PROPERTIES OF MALAYSIAN FIRED CLAY BRICKS AND THEIR EVALUATION WITH INTERNATIONAL MASONRY SPECIFICATIONS – A CASE STUDY ZAINAB ARMAN ALI UNIVERSITI TEKNOLOGI MALAYSIA
Jul 28, 2015
PROPERTIES OF MALAYSIAN FIRED CLAY BRICKS AND THEIR
EVALUATION WITH INTERNATIONAL MASONRY SPECIFICATIONS
– A CASE STUDY
ZAINAB ARMAN ALI
UNIVERSITI TEKNOLOGI MALAYSIA
PROPERTIES OF MALAYSIAN FIRED CLAY BRICKS AND THEIR
EVALUATION WITH INTERNATIONAL MASONRY SPECIFICATIONS
– A CASE STUDY
ZAINAB BINTI ARMAN ALI
A thesis submitted in fulfilment of the
requirements for the award of the Degree of
Master of Engineering (Structure and Materials)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
MAY 2005
iii
This thesis is dedicated to the people very dear to my heart:
my late parents, Arman Ali Hj Mohibullah and Zabedah Hamzah
my husband, Ayob Sharif
and my children…
Amlina, Aliza, Alira, Afandi Akmal, Alia Atika and Arfa Adlina
iv
ACKNOWLEDGEMENTS
The author wish to acknowledge the guidance, advice and assistance
given by her supervisor, Associate Professor Dr. Faridah Shafii and to thank her
for her encouragement and friendship, without which this thesis would not be
possible. The author is also greatly thankful to her for the limitless time she spent
in helping through with the writing of the thesis.
The author would like to acknowledge the support awarded by the
Government of Malaysia under the IRPA scheme in funding this research.
Appreciation is also due to Claybricks & Tiles Sdn Berhad for its contribution in
providing the bricks used in this research.
To the staff of concrete laboratory of the Civil Engineering Faculty of
UTM, thanks are due to the technicians, Ros, Amirul and Shahrul for helping
with works in the laboratory and sampling activity at the factory. Special thanks
are conferred to dear friends at the Faculty of Civil Engineering especially Zaiton
Haron who had given the author a lot of encouragement and motivation at the
beginning of the research. The author is also grateful to Dr. Zalina Daud of the
Science Faculty of UTM for her assistance in enlightening the mathematics of
statistics and Encik Yasin for his help in the Chemistry Laboratory.
Last but not least the author would like to thank all members of her family
especially the children who had given a hand on some computations and
computer skills.
v
ABSTRACT The research examined and assessed the properties of Malaysian fired clay
bricks to provide information for the development and revision of Malaysian Standard MS 76:1972. Some laboratory investigations on bricks were conducted in conjunction with the use of various masonry standards to evaluate the compressive strength, dimensional tolerances, water absorption, initial rate of suction, efflorescence, density and soluble salt content. The test methods were mostly based on MS 76:1972 and BS 3921:1985 and in some cases new testing approaches were adopted to assess new property requirements not catered in existing masonry specifications. The analysis on random samples indicated the acceptance of the use of a normal probability theory even for data with values of coefficient of variation close to 30%. In the case where the coefficient of variation exceeded 30 % the log-normal probability function applies. The statistical control charts traced data homogeneity for the population and data lying beyond the 5 % confidence limit, which were not accounted for in the analysis. The compressive strengths of facing bricks ranged from about 40 N/mm2 to 50 N/mm2 with lower values for common bricks, i.e. 30 N/mm2 to 40 N/mm2. These ranges of compressive strengths fall in the top range specified in Singapore Standard, SS 103:1974. The compressive strengths specified in ASTM were based on dry curing whilst British Standard, Singapore Standard and Malaysian Standard were tested in saturated conditions. Curing methods affect compressive strength with air curing giving higher values. Water absorption for the bricks under investigation range from 10 % to 12 % and therefore do not fit in the category of Engineering A or B of MS 76:1972 and BS 3921:1985, however satisfy the requirements for the categories of SW (severe weathering) bricks in ASTM. The dimensions satisfy the tolerances given in BS 3921:1985 except for the height. However, the dimensional tolerance fits the T1 category of the European Standard EN 771-1. The initial rate of suction for the bricks ranged from 1.4 to 2.0 kg/min/m2 indicating high suction property thus implying the necessity of wetting bricks before laying. Efflorescence does not seem to be a major problem hence these bricks could be satisfactorily used for facing construction purposes without resulting in salt deposition on the surfaces. The range of density (1760 to 1800 kg/m3) exhibited by the bricks satisfy the sound insulation requirements specified in the United Kingdom Building Regulations. In this research a method of predicting the compressive strength of bricks when laid in the different orientations was derived. This is a useful means of estimating the compressive strength of brick in practice where test are only conducted on the bed face. The research also highlighted a method of estimating the porosity of bricks for values of known water absorption.
vi
ABSTRAK
Penyelidikan ini mengkaji dan menilai sifat-sifat kejuruteraan bata tanah liat
bakar negara bagi membekalkan maklumat yang diperlukan untuk pembangunan Standard Malaysia MS 76:1972. Beberapa ujian makmal ke atas bata telah dijalankan selaras dengan penggunaan beberapa standard masonry untuk menganalisis kekuatan mampatan, toleransi pendimensian, penyerapan air, kadar resapan awal, ketumpatan, kesan peroi dan kandungan garam larut. Sebahagian besar ujian-ujian ini adalah berdasarkan kaedah MS 76:1972 dan BS 3921:1985 manakala pendekatan ujian semasa juga digunakan bagi menganalisis ciri-ciri baru yang tidak terkandung dalam spesifikasi sedia ada. Analisis sampel yang dipilih secara rawak menunjukkan penerimaan penggunaan teori kebarangkalian normal walaupun untuk data di mana nilai pekali perubahan menghampiri 30 %. Bagi kes dimana nilai pekali perubahan melebihi 30 %, fungsi kebarangkalian log-normal digunakan. Carta kawalan statistik digunakan untuk mengesan kehomogenan data dan data melampaui 5 % had keyakinan yang tidak diambil kira di dalam analisis. Kekuatan mampatan bata permukaan adalah antara 40 hingga 50 N/mm2 manakala bata biasa mempunyai nilai lebih rendah iaitu 30 hingga 40 N/mm2. Julat kekuatan mampatan ini tergulung dalam kategori tertinggi Standard Singapura, SS 103: 1974. Kekuatan mampatan dalam spesifikasi ASTM adalah berdasarkan bata diawet udara. Berbeza dengan Standard British, Singapura dan Malaysia, di mana bata di uji dalam keadaan tepu. Pengawetan udara memberikan nilai yang lebih tinggi. Penyerapan air adalah antara 10 hingga 12 %. Nilai ini tidak menepati keperluan MS 76:1972 dan BS 3921:1985 untuk kategori bata kejuruteraan A dan B. Walau bagaimanapun ia memenuhi syarat yang ditentukan dalam spesifikasi ASTM bagi bata jenis SW (terdedah pada kesan cuaca yang teruk). Dimensi bata dapat memenuhi keperluan toleransi pendimensian bagi standard BS 3921: 1985, kecuali ketinggiannya. Di bandingkan dengan Standard Eropah EN 771-1 pula, didapati ia menepati kategori T1. Kadar resapan awal bata ialah dari 1.4 hingga 2.0 kg/min/m2, menunjukkan ciri resapan yang tinggi, oleh itu bata perlu dibasahkan sebelum diikat. Bata tidak menghadapi masalah peroi, jadi ia boleh digunakan sebagai bata permukaan tanpa berlaku pemendapan garam di permukaannya. Julat ketumpatan bata ialah 1760 hingga 1800 kg/m3, sesuai bagi penggunaan dinding bangunan dengan nilai rintangan kebisingan memenuhi spesifikasi kanun bangunan di United Kingdom. Dalam penyelidikan ini kaedah untuk meramalkan kekuatan mampatan bata apabila disusun dengan orientasi yang berlainan telah dapat dihasilkan. Kaedah ini berguna bagi menganggarkan kekuatan mampatan bata secara praktikal dimana ujian mampatan hanya dilakukankan di permukaan atas bata. Kajian ini juga menerangkan kaedah menganggarkan keliangan bata daripada nilai penyerapan airnya.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
TITLE PAGE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xiii
LIST OF FIGURES xviii
LIST OF SYMBOLS AND ABBREVIATIONS xxi
LIST OF APPENDICES xxii
1 INTRODUCTION 1
1.1 History and Development of Masonry 1
1.2 Manufacturing of Clay Bricks 2
1.3 Construction Requirements for Masonry and
the Needs for Specification
3
viii
1.4 Masonry Standardisation and International
Development
4
1.5 Defining the Contents for Standard
Specifications
5
1.6 Research Problem 6
1.7 Aim and Objectives of the Research 8
1.8 Scope of Work 9
1.9 Layout of Thesis 10
2 LITERATURE REVIEW 12
2.1 Introduction 12
2.2 Compressive Strength 12
2.2.1 Strengths Variability 12
2.2.2 Brick Strength and Masonry Strength 13
2.2.3 Effects of Brick Type and Geometry 15
2.2.4 Effects of Test Methods and
Measurements
15
2.3 Dimensional Tolerance 17
2.4 Water absorption 19
2.5 Initial Rate of Suction 22
2.6 Soluble Salt Content and Efflorescence
Effects
24
2.7 Density 24
2.8 Brick Specifications in International
Standards
26
2.8.1 Compressive Strengths 26
2.8.2 Water Absorption 28
ix
2.8.3 Initial Rate of Suction (IRS) 29
2.8.4 Dimensional Tolerance 30
2.8.5 Efflorescence 33
2.8.6 Soluble Salt Content 35
2.9 Test Methods and Measurements in
International Standards
37
2.9.1 Methods of Sampling for Tests in
International Standards
37
2.9.2 Compressive Strengths 38
2.9.3 Water Absorption 39
2.9.4 Initial Rate of Suction 41
2.9.5 Dimensional Tolerance 41
2.9.6 Efflorescence 42
2.10 Conclusions 49
3 LABORATORY TESTS ON PHYSICAL
PROPERTIES OF BRICKS
54
3.1 Introduction 54
3.2 Sampling of Bricks 54
3.3 Testing Programme 55
3.4 Dimensional Tolerance 58
3.5 Density 61
3.6 Initial Rate of Suction 63
3.7 Water Absorption (5-hours boiling test) 66
3.8 Compressive Strength 67
3.9 Soluble Salt Content 72
3.10 Efflorescence 79
x
4 STATISTICAL ANALYSIS OF TEST SPECIMENS 81
4.1 Introduction 81
4.2 General Approach for Analysing Sample 81
4.2.1 Description of Data 82
4.2.2 Histograms and Normal Distribution
Curve
84
4.2.3 Log-normal Distribution Curve 86
4.2.4 Derivation of Population Estimates 87
4.2.5 Hypothesis Testing 89
4.2.5.1 Analysis of Variance
(ANOVA)
89
4.2.5.2 Control Charts 90
4.3 Application of Statistical Methods for
Samples Under Investigation
93
4.3.1 Description and Presentation of
Sample Data
96
4.3.2 Test for Data Homogeneity 103
4.3.3 Determination of Sample Variance
Using the ANOVA
105
4.3.4 Estimates of Population Mean 107
4.4 Conclusions 107
5 RESULTS AND DISCUSSIONS 110
5.1 Introduction 110
5.2 Compressive Strength 110
5.3 Dimensional Tolerance 125
xi
5.3.1 Overall Dimension of 24 Bricks 125
5.3.2 Dimension of Individual Brick for
Length, Width and Height
125
5.4 Water Absorption 135
5.5 Initial Rate of Suction 138
5.6 Density 142
5.7 Efflorescence 146
5.8 Soluble Salt Content 146
6 APPLICATION OF RESEARCH FINDINGS 148
6.1 Relationship of Aspect Ratio to Compressive
Strength
148
6.2 Relationship of Water Absorption to Porosity
and Compressive Strength
151
7 CONCLUSIONS AND RECOMMENDATIONS
FOR FURTHER WORK
154
7.1 Conclusions 154
7.2 General Conclusions 154
7.3 Detailed Conclusions 155
7.3.1 Compressive Strength 155
7.3.2 Water Absorption 156
7.3.3 Dimensional Tolerance 157
7.3.4 Initial Rate of Suction 157
7.3.5 Soluble Salt Content 156
7.3.6 Density 158
xii
7.4 Recommendations for Further Work 158
REFERENCES 161
APPENDICES 165
xiii
LIST OF TABLES
TABLE TITLE PAGE
2.1
Compressive strengths of bricks tested in different
orientations (Hendry, 1997)
16
2.2 Aspect Ratio Factor (Ka) 17
2.3 Limits of durability indices (Surej et al., 1998) 21
2.4 Characteristic flexural strengths and levels of water
absorption (BS 5628 Pt. 1, 1985)
21
2.5 Typical sound insulation values of masonry walls
(Curtin et al., 1995)
25
2.6 Classification of bricks by compressive strength and
water absorption (BS 3921:1985)
26
2.7 Physical requirements for building bricks (ASTM C
62-89a, 1990)
27
2.8 Characteristic compressive strength in accordance to
Australian Standard (AS 1225:1984)
27
2.9 Dimensional tolerance based on measurement of 24
bricks and coordinating and work size in accordance to
British Standard (BS 3921:1985)
30
2.10 Dimensional tolerance in accordance to Australian
Standard (AS 1225 – 1984)
31
2.11 Dimensional tolerance of facing bricks in accordance
to ASTM C 216-90a (1990)
32
2.12 Dimensional tolerance for mean value of work size in
accordance to European Standard (prEN 771-1, 2000)
33
xiv
2.13 Dimensional tolerance for range of work size in
accordance to European Standard (prEN 771-1)
33
2.14 Classification of bricks in accordance to dimensional
deviation limits in Singapore Standard (SS103: 1974)
33
2.15 Levels of efflorescence in British Standard (BS
3921:1985)
34
2.16 Levels of efflorescence for the Australian Standard
(AS 1225 – 1984)
35
2.17 Levels of efflorescence in Singapore Standard
(SS103: 1974)
35
2.18 Maximum salt content for the low category (L) in
accordance to British Standard (BS 3921:1985)
36
2.19 Soluble salt content categories in accordance to
European Standard (prEN 771-1)
37
2.20 Sample size for tests in international standards 38
2.21 Comparison of water absorption from 5-hr boiling and
the 24-hr cold immersion tests using whole brick and
brick lumps (Khalaf and DeVenny, 2002)
40
2.22 Test methods and measurements for compressive
strength in international standards
43
2.23 Test methods and measurements for water absorption
in international standards
44
2.24 Test methods and measurements for initial rate of
suction in international standards
45
2.25 Test methods and measurements for dimensional
tolerance in international standards
46
2.26 Test methods and measurement for efflorescence in
international standards
48
3.1 Testing programme 56
3.2 Overall dimensions of 24 bricks 58
3.3 Individual brick measurement of length, width, and
height for all batches.
59
3.4 Density of bricks for Batch 1 62
xv
3.5 Initial rate of suction in samples for Batch 1 65
3.6 Water absorption of bricks for Batch 1 67
3.7 Compressive strength of common bricks tested on bed
face
70
3.8 Compressive strength of facing bricks tested on bed
face
71
3.9 Compressive strength of facing bricks tested on the
stretcher face
72
3.10 Compressive strength of facing bricks tested on the
header face.
72
3.11 Percentage of sulphate content in samples for all
batches
73
3.12 Standard calibration for calcium 75
3.13 Percentage of calcium in samples for all batches 76
3.14 Standard calibration for sodium and potassium 76
3.15 Percentage of potassium in samples for all batches 77
3.16 Percentage of sodium in samples for all batches 78
3.17 Standard calibration for magnesium 78
3.18 Percentage of magnesium in samples for all batches 79
4.1 Components of variance from ANOVA 90
4.2 Water absorption of specimens in each sample for
facing brick
98
4.3 Frequency distribution of data for facing bricks 99
4.4 Normal and log-normal curve fit for water absorption 100
4.5 Normal and log-normal curve fit for compressive
strengths of common bricks
101
4.6 Comparisons of 33 percentile values from normal and
log-normal curve for compressive strength of common
brick
103
4.7 Probability that x will not be exceeded 103
4.8 Sample means and ranges for water absorption 104
xvi
4.9 Control limits for means and ranges for water
absorption
104
4.10 Samples accounted for in the estimate of population
mean for water absorption
106
4.11 ANOVA and components of variance for water
absorption
106
5.1 Compressive strength of specimens in each sample for
facing bricks tested on bed face
111
5.2 Compressive strength of specimens in each sample for
facing bricks tested on stretcher face
112
5.3 Compressive strength of specimens in each sample for
facing bricks tested on header face
112
5.4 Normal curve fit for compressive strength of facing
bricks tested on bed and stretcher face
113
5.5 Log-normal curve fit for compressive strength of
facing brick tested on header face
114
5.6 ANOVA and variance components for compressive
strengths of facing bricks tested on bed, stretcher and
header faces
117
5.7 Compressive strength of facing brick when tested on
bed face as computed from net areas
120
5.8 Compressive strength of facing and common bricks
and standard requirements
122
5.9 Compressive strength of specimens in each sample for
common bricks
123
5.10 Overall measurement of length, width and height of 24
bricks and individual brick dimensional deviations
from work size
126
5.11 Dimensional deviations of brick from work size and
comparisons with values of dimensional tolerance for
BS 3921:1985 and prEN 771-1
128
xvii
5.12 Individual brick dimensions for length, width and
height in all samples
130
5.13 Mean dimensions of individual length, width and
height of brick compared with British Standard (BS
3921:1985)
135
5.14 Water absorption of specimens in each sample for
facing bricks
135
5.15 Comparison of water absorption with limits specified
by British Standard and ASTM
137
5.16 Relationship between characteristic flexural strengths
and levels of water absorption (BS 5628 Pt. 1)
138
5.17 Computed values for initial rate of suction of
specimens for facing bricks based on gross area of
immersion
139
5.18 Computed values for initial rate of suction of
specimens of facing bricks based on net area of
immersion
142
5.19 Density of specimens in each sample for facing bricks
143
5.20 Density of bricks for walls and walls with plaster finish
(Building regulations of the UK)
145
5.21 Typical sound insulation values of masonry walls
(Curtin et al., 1995)
145
5.22 Percentage of soluble salts in samples from all batches 146
6.1 Relationship between bricks compressive strength,
water absorption and porosity (Khalaf, 2002)
152
xviii
LIST OF FIGURES
FIGURES TITLE PAGE
2.1 Mean compressive strength of walls against brick
strength for 102mm thick brickwork in various mortars
14
2.2 Expansion of kiln-fresh bricks due to absorption of
moisture from atmosphere
19
2.3 Relationship of flexural strength of brickwork with
water absorption of bricks in plane of failure (a) and (c)
parallel to bed joints and (b) and (d) perpendicular to
bed joints (Morton, 1986)
22
3.1 Sequence of testing 56
3.2 Overall Measurement of (a) length, (b) width
and (c) height for 24 bricks
60
3.3 Apparatus for the measurement of density 63
3.4 Apparatus for measuring the initial rate of suction 65
3.5 Apparatus for water absorption test 66
3.6 Compressive machine -Tonipact 3000 69
3.7 a Bricks tested on bed face 69
3.7 b Bricks tested on stretcher face 69
3.7 c Bricks tested on header face 70
3.8 A schematic diagram of an atomic absorption
spectrometer (Hammer, 1996)
74
3.9 Calibration curve for detection of calcium 75
3.10 Calibration curve for detection of sodium and
potassium
77
3.11 Calibration curve for detection of magnesium 78
xix
3.12 Efflorescence test 80
4.1 Mean, median and mode in a distribution skewed to the
right.
84
4.2 Areas under normal probability curve 88
4.3 T-distribution curves for various values of n (Chatfield,
1978)
89
4.4 Control charts for sample means and ranges (Neville,
1985)
93
4.5 Process of statistical analysis 95
4.6 Histogram, normal curve and log-normal curve, for
water absorption of bricks
99
4.7 Histogram, normal and log-normal curve for
compressive strength of common bricks (c.v.
approaching 30%)
103
4.8 Control chart for means values of water absorption
105
4.9 Control chart for ranges of water absorption. 105
5.1 Histogram, normal and log-normal curve for
compressive strength of facing bricks tested on (a) bed
face (b) stretcher face (c) header face
115
5.2 Control charts of mean values and ranges for
compressive strengths tested on (a) bed face (b)
stretcher face (c) header face
116
5.3 Relationship between compressive strength and h/t
ratio of bricks
119
5.4 Relationship between the computed compressive
strength (based on net loaded area of bed face) to h/t
ratio
121
5.5 Histogram and normal curve for compressive strength
of common bricks
123
5.6 Control charts of mean values and ranges of samples
for compressive strength of common bricks
125
5.7 Comparison of overall dimensions of (a) length (b) 127
xx
width and (c) height with allowable range of British
and Singapore Standard
5.8 Histogram and normal curve for individual dimensions
of length, width and height of bricks
133
5.9 Control charts for mean values and ranges of samples
for (a) length (b) width and (c) height of bricks
134
5.10 The histogram and the normal curve fit for water
absorption of bricks
136
5.11 Control chart of mean values and ranges of samples
for water absorption of bricks
137
5.12 Histogram and normal curve fit for IRS based on gross
area of immersion
140
5.13 Control charts for means and ranges for IRS based on
gross area of immersion
140
5.14 Histogram and normal curve fit for density of bricks 144
5.15 Control charts for mean values and ranges of samples
for density of bricks
144
6.1 Relationship between compressive strength and h/t
ratio of bricks
149
6.2 Orientations of bricks in a brick laying (a) header face
(b) bed face and (c) stretcher face.
149
6.3 Relationship of water absorption with porosity from
Table 6.1
152
6.4 Relationship of porosity with compressive strength
from Table 6.1
152
xxi
LIST OF SYMBOLS AND ABBREVIATIONS
ANOVA - analysis of variance
Mpa - Megapascals
AS - Australian Standard
ASTM - American Standard of Testing Materials
BS - British Standard
c.v. - Coefficient of variation
df - Degree of Freedom
EN - European standard
MS - Malaysian Standard
MS - Mean of Squares
n - Sample size
N.H. - Null Hypothesis
NZS - New Zealand Standard
R - Range
s - Sample standard deviation
SS - Sum of squares
Std. dev. - Standard deviation
Var - Variance
ν - Coefficient of variation
x - Mean of sample means
µ - Population mean
σ - Population standard deviation 2s - Sample variance
x - Sample mean
xxii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A1. Results of Tests Specimens for Dimensional 166
Tolerance of Individual Bricks
A2. Results of Test Specimens for Density of Bricks 170
A3. Results of Tests Specimens for Initial Rate 175
of Suction of Bricks
A4. Results of Tests Specimens for Water Absorption 183
of bricks
A5. Results of Tests Specimens for Compressive 188
Strength of Bricks
B. Statistical Tables 200
CHAPTER 1
INTRODUCTION
1.1 History and Development of Masonry
The history of civilisation is synonymous to the history of masonry. Man’s
first civilisation, which started about 6000 years ago, was evident by the remains of
the Mesopotamians masonry heritage. During those days masonry buildings were
constructed from any available material at hand. The Mesopotamians used bricks,
made from alluvial deposits of the nearby River Euphrates and Tigris to build their
cities beside these two rivers. Where civilisation existed in the vicinity of mountains
or rocky outcrops, stone was used. The Egyptians pyramids that existed along the
rocky borders of the Nile valley were examples of such stone masonry. In the
Eastern civilisation remains of historical masonry is the reputed Great Wall of
China, which is considered as one of the seven construction wonders in the world.
The materials used in the construction varied from tamped earth between timbers
and adobe i.e. sun-dried bricks to local stones and kiln-fired bricks. The part of the
wall that remains until today is mainly those made of bricks and granite.
The early forms of masonry application in Malaysia dated back about 350
years ago with the construction of the Stadthuys in Malacca, built by the Dutch in
1650. A more modern form of masonry construction was initiated by the British who
colonised the then Malayan Peninsula. Brickwork buildings were at that time built
specially for government offices, quarters and residential. The administrative block,
2
Sultan Abdul Samad building built in 1894 and given a face-lift during the Fourth
Malaysian Plan (1981 – 1985) is an example of a masonry heritage, which stands as
a remarkable landmark of Kuala Lumpur.
In its early forms masonry structures were built without any structural
calculations. Units of masonry consisting of stones or bricks were either stacked dry
or bonded with any adhesive material to form structures and self weight being used
to stabilise the construction. The Great Wall of China for example, stood at 6.5
meters wide at the base and 5.8 meters at the top, constructed at this massive scale
mainly for stability.
With the advancement of engineering technologies and manufacturing the
development of masonry units and their applications have extended beyond the
conventional approaches and processes leading to a more efficient design and
economy. Situations where considerable lateral forces have to be resisted, the low
tensile strength of bricks could be overcome by using reinforced masonry.
Construction where greater span lengths is desired, post tensioned bricks are used,
making it possible for bricks to be used in large single cell buildings.
1.2 Manufacturing of Clay Bricks
Clay brick is the most extensively used type of masonry units throughout the
world. Its widespread use is mainly due to the availability of clay and shale in most
countries. Its durability and aesthetics appeal also contribute to its extensive
application in both load bearing and non-load bearing structures.
Manufacturing techniques for the production of clay bricks have changed
from the initially hand moulded processes to modern mechanisation. At present
bricks are formed either by the process of extrusion, moulding or dry pressing.
These advance techniques of manufacturing allow greater flexibility in its design;
with a more efficient and varied burning process a wide range of products can be
manufactured. Longer burning processes also tend to produce denser units thus
3
allowing its use for load bearing purposes. Other variations including appearance,
colours, textures, sizes and physical properties could be designed accordingly to the
type of bricks to be produced and its application.
1.3 Construction Requirements for Masonry and the Needs for Specification
Due to the varying manufacturing process and the raw materials, bricks
produced could have a wide range of variability in its appearance and physical
properties making brick a versatile building unit in construction. Bricks are of great
importance for load bearing walls in low and medium rise buildings and for non-
load bearing walls as cladding for buildings. It serves several functions including
structure, fire protection, thermal and sound insulation, weather protection and
subdivision of space.
The several functions of bricks and the availability of a variety of bricks that
are able to serve the different construction requirements therefore require an
efficient and consistent guideline in achieving a safe, efficient and economical
design. This is often dictated by specifications and standards.
Load bearing brickworks, besides functioning as subdivision of space should
also have the load carrying capacity, necessary thermal and acoustics insulation as
well as fire and weather protection. Consequently, bricks in load bearing
applications should have adequate strength so that it could safely carry the loads
imposed by the structure and be able to meet the other physical requirements
specified in standards. On the other hand, non-load bearing brickworks are non-
structural, which are designed not to carry load and therefore consideration for
strength is of less importance compared to the requirements needed in load-bearing
masonry.
A damp-proof-course in brick walls at ground floor level prevent moisture
from the ground rising through the bricks and mortar and causing dampness in the
lower parts of the ground floor walls. For this reason bricks used as damp-proof-
4
course must be sufficiently impermeable and this could be ascertain through its
water absorption property.
Facial bricks are mostly produced as quality bricks with high compressive
strength and low water absorption as they can be efficiently applied as structural
bricks with aesthetics quality for use in external walls. These bricks should also
possess other physical requirements essential in good brickwork practices.
1.4 Masonry Standardisation and International Developments
The earliest standard was for weights and measures, which could be traced
back to the ancient civilisation of Babylon and early Egypt (IEEE, 2001). However,
the importance of standardisation was only fully realised until during the industrial
revolution of early nineteenth century.
As for masonry, standards had evolved through research discoveries and the
experience acquired over the years in the use of masonry. Each masonry standard is
different and unique for any country as it incorporates the national requirements. As
such the brick specifications for Australia, America, Britain differs. However, the
basic approach may be similar, to some extent. These standards were developed
more than several decades ago and used the prescriptive approach.
The trend towards globalisation requires harmonisation of standards and this
is evident with the European Standard (EN), which was established to encourage
trade between the European member states and the EN 771 became the new standard
thus setting new specifications of masonry units for Europe.
5
1.5 Defining the Contents for Standard Specifications
The international masonry standards define specifications by consideration
of the parameters described in the foregoing paragraph.
With respect to the mechanical properties of bricks, the most important is
compressive strength, which as well as being direct importance to the strength of a
wall, serves as a general index to the characteristics of the bricks. It is measured by
a standardised test, the results rely to a certain degree on the standard procedures
and conditions for testing prescribed in standards.
Bricks vary in their dimensions due to the variable shrinkage occurring
during and after manufacturing. This dimensional variability should be a minimum
in facing brickwork to ensure even joints for an aesthetically pleasant wall.
Water absorption of brick, which indicates bricks permeability, is dependent
on its porosity. Porous bricks will allow water to penetrate a wall more easily thus
contributing to problems of water seepage in masonry walls. This is an important
factor to be considered in masonry materials especially for tropical regions where
there is abundance of rain. In temperate countries, water absorption property of a
brick is used in standards in defining bricks durability in terms of its resistance to
freezing and thawing.
The initial rate of suction, which is the amount of water sucks by the brick
from mortar during laying, affects the bond between bricks and mortar in a
brickwork and is a required parameter in design of flexural walls. Optimum bond
strength could be achieved by ensuring the initial rate of suction is within the
specified limits in standards.
The other property, which is known to affect the appearance of a wall and
therefore critical in facing bricks is the effects of efflorescence. The whitish salts
deposits that appear on bricks surfaces are called efflorescence. Efflorescence is
caused by the presence of soluble salt in the bricks and water as the carrier, which
transport the salts to bricks surfaces.
6
The content of detrimental soluble salts in bricks also affects the durability of
brickwork. For example, if the amount of water-soluble sulphate exceeds the
allowable, sulphate attack will occur which will cause the disintegration of
brickwork and thus affecting its durability.
The various standards adopt different methods of measurement for
evaluating the properties of bricks. Limits may be specified to provide guidelines in
achieving satisfactory results of the final construction.
The Malaysian standard MS 76:1972 was a mere adoption of BS 3921,
excluding certain properties not relevant to Malaysian requirements, and therefore
limiting to a number of main properties only. With the advent of highly technical
manufacturing techniques and subsequently the presence of new range materials,
materials may have to be tested for additional physical and chemical properties, to
ensure its best performance after laid on construction site.
An improvement of Malaysian Standard is essential to cater with current
technical requirements and ensuring effectiveness of masonry applications. This
entailed investigations on brick properties before any recommendations could be
made on the materials and limits set to achieve satisfactory results in construction.
The research examine the various masonry specifications including
Malaysian Standard in an attempt to establish a better understanding of the various
standards and in deriving recommendations for Malaysian applications relating to
new technical requirements.
1.6 Research Problem
The development of the existing Malaysian standard MS 76:1972
(Specification for bricks and blocks of fired brickearth, clay or shale) were based on
BS 3921:Part 2:1969 (Specification for Bricks and blocks of fired brick-earth, clay
or shale). The British Standard had been revised twice, the latter versions being BS
7
3921:1974 and the existing BS 3921:1985. The revisions incorporate significant
details pertaining to material requirements and construction practices. Some of the
significant changes in existing British Standard BS 3921:1985 (British standard
specification for clay bricks) include bricks classifications, designations for
durability and new requirements on physical properties and revision of testing
methods.
The shift of British standard to European standard and eventual withdrawal
of the British Standard, therefore requires the Malaysian Standard to be revised
accordingly to suit to current market products and requirements for masonry
applications. Subsequently a research is necessary to study the various international
masonry specifications in providing a detailed understanding of the specifications
requirements, before recommendations be made to improve the existing brick
specification for Malaysia. These efforts will also facilitate the development of a
national standard capable of complying with standard global requirements.
In producing a national brick specification, data on local brick performance
are required to guide and support the new set of recommendations proposed for the
new standard.
The Malaysian Standard MS 76:1972 requires some essential amendments to
its specification to cater for present masonry application. For example, the existing
specification does not require any limit of salt content for ordinary quality facing
and common bricks, which are meant for external applications. Limits of soluble salt
content in bricks are essential as a preventive measures for salt deposition and
detrimental chemical reaction, which could damage the appearance of facial
brickwork construction. Investigation on the initial rate of suction property for
Malaysian bricks is crucial as this property, which is at present not included in the
specification, is an important criterion in structural brickwork design and
calculations.
The supplementation of data relating to local bricks performance is essential
to guide and support the new recommendations proposed for the improved
standard mentioned above.
8
1.7 Aim and Objectives of the Research
The aim of the research is to establish a detailed understanding of brick
properties through some laboratories investigations in conjunction with use of
various masonry standards to assess the material performance. The results of these
work supplemented with statistical studies and reviews of past research provides a
useful guidance to brick properties for local production. These work will also
provide data pertaining to current production of bricks which may be considered
significant to any revision or amendment made to the existing Malaysian Standard
for masonry MS 76:1972, currently under revision.
The objectives of the research are:
(i) To conduct an experimental investigation on compressive strength,
dimensional tolerances, density, initial rate of suction, water
absorption, efflorescence and soluble salt content of facing bricks.
(ii) To examine the compressive strength of common bricks.
(iii) To examine the compressive strengths of bricks tested in various
orientations as recommended by Australian/New Zealand and
European standard. Thus establish the relationship between the aspect
ratio (h/t) and compressive strength of bricks.
(iv) To study the density of bricks and its relation to acoustics properties
of masonry.
(v) To examine the statistics of locally manufactured bricks and the
respective control charts representing the population of bricks under
study.
(vi) To establish the relationship of water absorption, porosity and
compressive strength of bricks and to predict compressive strength
from known values of water absorption and porosity.
9
The studies were conducted through laboratory investigations of local bricks
and literatures establishing the state-of-the art of previous works and references to
international specification of masonry.
1.8 Scope of Work
The research is a case study, which dealt with the investigation of fired clay
facing and common bricks from a local manufacturer. The bricks were tested under
laboratory conditions as specified by the respective standards. The brick properties
examined were confined to studies on compressive strength, dimensional tolerance,
density, initial rate of suction, water absorption, efflorescence and soluble salt
content. Majority of the tests were based on the Malaysian Standard MS 76:Part 2
1972, which is basically an adoption of British Standard, BS 3921:1969. Since then
the British Standard for masonry has been revised several times to accommodate
changes for current needs.
Other standards used in the study were ASTM (American society for testing
and material), Australian/New Zealand standard, Singapore standard and European
standard. These standards formed the major references for comparisons of the
applications and methods of testing and determining the bricks properties
investigated in this programme. They form the major references for discussions in
this thesis.
Studies on bricks density are new to masonry and this was included in this
research in aligning with the new recommendations specified by the European
Standard.
The outcomes of the laboratory investigations were based on a local brick
manufacturer and therefore the results are inconclusive to suggest a representation of
the national population, however provides some guides to the properties of
Malaysian clay bricks.
10
1.9 Layout of Thesis
Chapter II describes the significance of physical and chemical properties of
bricks and its effects upon masonry behaviour. A review was conducted to examine
the various international masonry specifications, the recommended methods of
testing and measurements and comparisons between them. A considerable amount of
attention was given to the studies on masonry specifications by Malaysian Standard,
British Standard, and the Eurocode. Comparisons were also made by referring to
Australian/New Zealand Standard and ASTM. The limitations and advantages of the
various standards were highlighted and these form the basis of knowledge for the
work carried out in this thesis and where possible recommended for future standard
development.
Chapter III describes the laboratory works to identify the physical and
chemical properties of local clay bricks in providing data for Malaysian bricks. The
compressive strength, density, dimensions, water absorption, initial rate of suction,
efflorescence and salt content were investigated mainly using British Standard and
in specific cases other standards were also used. The British Standard is regarded as
the main reference used in this research as it is used widely in practice in Malaysia.
Chapter IV presents the statistical analysis of bricks properties investigated
in Chapter III. The descriptive statistics of data were computed and the graphical
distribution of data shown by histograms and normal curves. The application of
control charts was presented for testing data homogeneity. The analysis of variance,
ANOVA was used to derive the components of variances in samples, which in turn
will be used to calculate the bricks population mean.
Chapter V presents the experimental and statistical results for the bricks
properties investigated in the programme. The results for every parameter were
discussed and compared to previous research works and specification requirements
set by existing international standards.
11
Chapter VI presents a method of predicting compressive strength and
porosity properties of bricks based on the findings of work carried out in this thesis.
Chapter VII presents the conclusions of the works and recommendations for
future studies.
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The properties of bricks affect the appearance and the quality of masonry
construction. Therefore, emphasis has been given by codes and standards to specify
the properties of units and component materials, in order to achieve the designated
durability, quality and strength.
This chapter presents works conducted on bricks for specifications
development and standardisations. Evaluation of bricks made on compressive
strengths, absorption properties, initial rate of suction, dimensional deviations,
efflorescence effects, soluble salt content and density i.e. the parameters contributing
to specification development.
2.2 Compressive Strength
2.2.1 Strengths Variability
The compressive strengths of bricks vary considerably with the material used
in manufacturing and the duration and degree of burning. Bricks compressive
13
strengths can be defined into three levels i.e. the high strength engineering bricks
with compressive strength ranging from 55 to 69 N/mm2, the medium strength
bricks range from 27 to 48 N/mm2 and the low strength brick range from
approximately 14 to 25 N/mm2 (Lenczner, 1972). Due to these considerable
variations, strengths of bricks are classified accordingly to its application in
construction. Bricks with compressive strengths of approximately 5 N/mm2 are
sufficient for the construction of low-rise buildings like dwelling houses
(Hendry et al., 1981). For high-rise structures, engineering bricks and those of high
compressive strengths should be used (Hendry, 2001).
The compressive strengths of bricks were associated with materials and
manufacturing features as highlighted by Grimm (1975). Additionally, the
compressive strength can be generally higher for the following cases:
• Units made of shale by the stiff mud process
• Burned at high temperatures
• Cored less than 35% of its gross area with no sharp re-entrant corners
• Units with small heights
2.2.2 Brick Strength and Masonry Strength
Compressive strength of a brick is important as an indicator of masonry
strength and as a result, brick strength has become an important requirement in
brickwork design. A considerable amount of past research and studies on masonry
(Hendry, 1990, Lenczner, 1972, Sahlin, 1971,) indicated that stronger bricks
contribute to greater brickwork strength.
Brickwork is strongest in compression and research shows that the
compressive behaviour of brickwork depends on the strength of brick and mortar.
However there is no suggestion of a direct relationship between the individual
component strength and the resultant masonry strength. The complex nature of
14
analysis for masonry (composite material) contributes to the difficulties in
establishing such relationship.
Some existing work based on the analysis of experimental data conducted on
102.5 mm and 215 mm thick walls (Hendry and Malek, 1990) showed that the
compressive strength of walls (f) could be estimated by the following equations:
For wall thickness of 102.5 mm 0.2080.5311.242 b mf f f= …(2.1)
For wall thickness of 215.0 mm 0.778 0.2340.334 b mf f f= …(2.2)
Where,
fb and fm are the brick and mortar compressive strengths respectively.
Equations 2.1 and 2.2 were represented graphically as shown in Figure 2.1
(Hendry, 1990) and has been used as a basis for estimation in design codes for
masonry, BS 5628 Part 1: 1985: Structural use of unreinforced masonry.
1:2:9 mortar1:1:6 mortar
1:1/2:41/2 mortar1:1/4:3 mortar
05
1015202530
0 20 40 60 80 100 120
Compressive strength of brick (N/mm2)
Com
pres
sive
stre
ngth
of w
all
(N/m
m2 )
Figure 2.1: Mean compressive strength of walls against brick strength for
102mm thick brickwork in various mortars (Hendry, 1990).
Brickwork strength can also be estimated by other simple relationship with
unit strength. Hendry et al. (1996) proposed that the compressive strength of
brickwork could be approximated to the square root of unit strength and to the third
15
or fourth root of the mortar cube strength. The Brick Development Association of
UK (1974) relates bricks with compressive strength of 35 N/mm2 to wall strength,
with a ratio of 0.3 to 0.35:1.
2.2.3 Effects of Brick Type and Geometry
The type and geometry of bricks whether solid, perforated, or hollow have
an effect on the compressive strength of masonry. Hendry (1990) reported an earlier
findings done by Schellbach (1971) on the compressive strengths of highly
perforated units, and reported that the highest ratio of masonry strength to brick
strength was obtained for bricks with perforation ratio of 38-43 %. Hendry (1990)
highlighted that holes of round shape or slots with round corners have no
distinguished effects on compressive strengths of brickwork, Conversely, a decrease
in compressive strengths of brickwork were observed for bricks with cores of
rectangular slots. Rectangular slots tend to initiate shear failure.
2.2.4 Effects of Test Methods and Measurements
The compressive strengths of brick are measured by loading bricks in
compression. Conventional tests require bricks to be loaded normal to its bed face
and the faces are capped or packed before testing to reduce the effects of roughness,
lack of plane and platen effects. Different materials could be used for packing or
capping. Malaysia/British Standard recommended soft capping using sheets of
plywood between loaded surfaces of bricks specimen. On the other hand, ASTM
specifies the use of hard capping consisting of either a thin layer of molten sulphur
compound or a gypsum plaster compound. Soft packing has the advantage of a
reduction in the time of preparation for testing and it has occasionally been claimed
that soft capping produced a more representative strength than hard capping
(Drysdale et al., 1994). Grimm (1975) highlighted that if a brick specimen is
unrestrained through the insertion of a teflon pad between brick and machine head
16
the compressive strength of the unit is further reduced. This is due to reduction in
effects of the machine platen.
Besides the influence of platen restraint and capping material, the
compressive strengths of bricks are also affected by the orientation of the specimen
during testing. Bricks tested on its bed, edge and end would give different
compressive strengths due to the different heights of the specimen. The platen effect
on the brick will be reduced with increase in height subsequently decrease its
compressive strength. Table 2.1 shows the work reported by Hendry (1997) on the
compressive strengths of bricks when tested in different orientations. Maximum
strength was achieved when tested on bed whilst minimum strength was obtained
when tested on end. Considerations for this shape factor are given its importance in
the European Standard prEN 771-1, which requires bricks compressive strength to
be declared with the intended orientation for testing.
Table 2.1: Compressive strengths of bricks tested in different
orientations (Hendry, 1997) Tested Brick type
On bed On edge On end
14 hole 74.3 26.2 10.4
10 hole 70.2 29.5 21.7
3 hole 82.0 53.2 40.2
5 slots 64.1 51.8 13.8
The influence on the shape factors was considered in the Australian Standard
AS/NZS 4456.4:1997, Masonry units and segmental pavers- Methods of tests. In
this standard, the compressive strength of brick is multiplied with a factor called the
aspect ratio factor, Ka which depends on the height to thickness ratio, to provide the
unconfined compressive strength. The unconfined compressive strength is given by
equation 2.3.
1000a
PC KA
= …(2.3)
Where,
C = unconfined strengths in megapascals.
17
P = total load at which the specimen fails in Kn.
A = net area in mm2
Ka = aspect ratio factor (Table 2.2)
Table 2.2: Aspect Ratio Factor (Ka) Height to thickness ratio 0 0.4 1.0 5.0 or more
Aspect Ratio Factor (Ka) 0 0.5 0.7 1.0
The curing of bricks specimen before testing also affects the compressive
strength of brick. Wet bricks tend to show lower strengths than dry ones. Grimm
(1975) reported that dry brick can be 15% stronger than wet ones.
2.3 Dimensional Tolerance
Fired clay bricks vary in size due to the varying property of natural clay and
variations in the manufacturing drying and firing conditions. The total variations,
which may take place due to variable shrinkage properties of clay during and after
manufacturing can account to approximately 5 to 15 % of original dimensions. Due
to the presence of this wide range of variability, dimensional tolerances are specified
in standards to achieve the desired dimensional consistency. This is important in
brickwork because it has been proven from research and observations that
dimensional variation would affect brickwork aesthetically as well as structurally
Bricks dimension should not vary more than the tolerance specified in
standards. Limits for dimensional tolerance is specified in facing brickwork to
ensure that sizes of bricks do not differ too much as to affect the appearance of a
wall. This is especially important for very short length walls and piers. Besides this,
research has also shown that careful control of dimensions would markedly increase
the speed of brick laying (Haller, 1964).
18
Previous research on masonry has shown that units with low dimensional
variation will produce a wall of higher compressive strengths. The use of bricks with
well-controlled dimensions is also essential for high strength brickworks since
brickwork with non-uniform joint thickness would be subjected to bending moments
and stress concentration. According to Grimm (1975), the compressive strength of
relatively short brick masonry prisms, built from conventional materials which were
concentrically loaded and tested in accordance to ASTM E477 (7) may be predicted
from the following equation:
' ' 8 2 6 11.42 10 ( 9.45 10 )(1 )m b cf f fζη ε− −= + × + …(2.4)
Where, '
mf = compressive strength of brickwork masonry prism
'bf = compressive strength of brick
ζ = prism slenderness ratio
η = material size factor
ε = workmanship factor and this factor depend upon the verticality of the
wall, dimensional variation and quality of mortar joints. For good
workmanship,
ε = 0.
It is evident from equation 2.4 that the dimensional variation constitutes the
workmanship factor, affects the compressive strength of brickwork.
Quality control measures during manufacturing are important to ensure that
bricks dimensions are within limits specified in standards. One of the causes for
variation lies partly with the mould and wearing of dies. Moisture movement within
the brick can also contribute to size variations after manufacturing. Clay bricks tend
to expand as they pick up moisture after being unloaded from the kilns. The
magnitude of this movement varies accordingly to types of bricks and brick firing
temperatures. About half of the expansion occurs within a few days after
manufacturing and the remainder gradually stabilised after a few months (Fig.2.2).
19
Therefore, generally bricks are only taken to the site two weeks after coming out
from the kilns.
71 100
Maximum Expansion
Expa
nsio
n
Days0
Figure 2.2: Expansion of kiln-fresh bricks due to absorption of
moisture from atmosphere. (Hendry et al., 1997)
2.4 Water Absorption
Water absorption of a brick is defined as the weight of water in a brick
expressed as a percentage of the brick’s dry weight. It varies roughly from 4.5 to 21
% and the variation is mainly due to the variable raw material and the manufacturing
process.
The extrusion process in the manufacturing produces denser brick in
comparisons to the moulded bricks and denser bricks in turn would exhibit less
absorption. This was proven through experiments (Sahlin, 1971), which showed that
extruded bricks contain small percentage of voids and therefore are less absorbent to
water.
The effects of bricks absorption property due to variable raw material used in
its manufacturing was shown by Surej et al. (1998) who reported the work carried
out by Kung (1987) on the effects of raw material to water absorption. The report
showed that within the normal brick firing temperature range, the water absorption
20
and the porosity of the burnt bricks increases with increasing calcium carbonate or
limestone content in the raw materials.
Water absorption of bricks is usually measured by the 5-hours boiling and
24-hours cold immersion test. The 24-hours cold immersion test allows water to be
absorbed into pores, which are easily filled under cold condition while the 5 hours
boiling test gives fully saturated condition where all pores are filled up with water.
The ratio of 24 hours cold immersion to maximum absorption in vacuum or
boiling (C/B ratio) gives the saturation coefficient, which is used to indicate bricks
durability. The saturation coefficient, which is actually a measure of the relative
open pore space present in brick is crucial during freeze-thaw action to
accommodate the volume change in water as it freezes. The saturation coefficient
ranges from about 0.4 to 0.95, the lower value of around 0.4 indicates high
durability and higher values of around 0.95, low durability (F. M. Khalaf and A. S.
De Venny, 2002).
Other durability indices have also been developed based on relationship of
porosity and water absorption. Table 2.3 shows the durability indices developed by
Surej et al. (1998). Theses durability indices, which are a function of porosity and
water absorption of bricks is shown in equation 2.5 and 2.6. DIAP(C) and DIAP(S)
refers to durability index based on absorption properties derived from the cold
immersion absorption property and the suction property respectively.
450.70 1( ) 387.98 0.87(2.94 )
CDIAP CB B
= + − + …(2.5)
450.70 4( ) 329.81 0.97(2.94 )
SDIAP SB B
= + − + …(2.6)
Where,
B is the absorption due to 5-hr. boiling.
C1 is the absorption due to 1-hr.immersion absorption.
S4 is the 4-hr. capillary suction achieved through similar test as in the initial
rate of suction.
21
Table 2.3: Limits of durability indices (Surej et al., 1998) Limiting Values
Index Durable Non-durable
DIAP(C) >90 <75
DIAP(S) >85 <70
Studies on the effects of water absorption to structural performance of fired
clay masonry shows that water absorption of masonry units has a relation with
flexural behaviour of masonry. Research carried out by the British Ceramic
Research Association on test wallettes to study the relationship of flexural strength
of brickwork and water absorption of bricks has derived the relationship between
flexural strength and water absorption (Figure 2.3). The curved line indicated in
brown is the 95 % confidence limit and this was approximated to the stepped line,
which relates to three levels of water absorption i.e. less than 7%, 7% to 12% and
beyond12% to the respective values of characteristic flexural strengths. These limits
of water absorption associated with the flexural strength of brickwork are used in BS
5628: Part 1 for design of laterally loaded walls (Table 2.4).
Table 2.4: Characteristic flexural strengths and levels of
water absorption (BS 5628 Pt. 1, 1985)
Characteristic flexural strength, fkx N/mm2
Plane of failure parallel
to bed joints Plane of failure perpendicular
to bed joints
Mortar designation (i) (ii) and
(iii) (iv) (i) (ii) and
(iii)
(iv)
Clay bricks having a water absorption less than 7% 0.7 0.5 0.4 2.0 1.5 1.2
Between 7 % and 12 % 0.5 0.4 0.35 1.5 1.1 1.0 Over 12 % 0.4 0.3 0.25 1.1 0.9 0.8
22
0
0.5
1
1.5
2
0 10 20 30
Water absorption %
Flex
ural
stre
ngth
N/m
m2
0
1
2
3
4
0 10 20 30
Water absorption %
Flex
ural
stre
ngth
N/m
m2
(a) (b)
0
0.5
1
1.5
2
0 10 20 30
Water absorption %
Flex
ural
stre
ngth
N/m
m2
0
1
2
3
4
0 10 20 30
Water absorption %
Flex
ural
stre
ngth
N/m
m2
(c) (d)
Figure 2.3 Relationship of flexural strength of brickwork with water
absorption of bricks in plane of failure (a) and (c) parallel to bed
joints and (b) and (d) perpendicular to bed joints (Morton, 1986)
2.5 Initial Rate of Suction
The initial rate of suction (IRS) denotes the amount of water sucked by the
brick upon contact with mortar during laying. The IRS, resulting from the presence
of capillary mechanism of the small pores in the bricks, is an important property in a
masonry construction since it affects the bond strength between the brick and mortar
thus affecting water tightness and durability of masonry.
BS Mortar Designation (i) 1 : ¼ : 3
BS Mortar Designation (iii) 1 : 1 : 6
23
Bricks with IRS less than 0.25 kg/m2.min can be considered as low suction
bricks whilst bricks with IRS more than 1.5 kg/m2.min can be regarded as high
suction bricks (Drysdale et al., 1994). Tests have indicated that IRS values between
0.25 to 1.5 kg/m2.min generally produce good bond strength when used with the
appropriate mortar designations. High suction bricks absorb water from the mortar
rapidly thus impairing bond properties. This water is needed for the proper hydration
of cement where the mortar contacts the brick. On the other hand, low suction bricks
do not absorb much water and hence the surplus water will float on to the surface of
mortar to result in poor initial and final bonding strength. However, recent tests to
evaluate the bond strength and water penetration of masonry built with low IRS
brick, demonstrated that flexural bond strength of very low IRS brick (less than 0.25
kg/m2.min) can equal or exceed those of higher IRA brick with proper selection of
mortar materials and type (BIA, 2001).
The initial rate of suction (IRS) is determined by the amount of water
absorbed through the bed face when immersed in 3mm depth of water for a period of
1 minute. The British Standard recognises the IRS as a crucial requirement for
highly stressed masonry and a test method to determine IRS is given in the appendix
of BS 3921:1985. However, no limit for IRS has been specified. On the other hand,
ASTM, gives guidance on limits for IRS. It recommends that bricks with IRS
greater than 30g/min per 30 in2 (equivalent to about 1.5 kg/ m2.min) should be
wetted prior to laying.
Wetting of bricks before laying are more vital for construction in hot weather
especially for highly absorptive bricks. However, the wetting of bricks has its
shortcoming. The bricks will have variable degree of wetness giving rise to variable
compatibility with mortar (Drysdale et al., 1994).
24
2.6 Soluble Salts Content and Efflorescence Effects
All clay bricks contain soluble salts originating from raw clay deposits. In a
brickwork, salts may also originate from mortar or drawn up from the ground.
Efflorescence, which is the white deposition of salts on bricks surfaces, occurs due
to the presence of these salts carried by water to the brick surfaces.
Salts leading to efflorescence are mostly sulphates of sodium, potassium,
magnesium and calcium salts. Efflorescence usually occurs in new constructions and
takes place when water-carrying salts evaporates leaving the salts depositions on
masonry surfaces. The dissolved salts in crystalline form lead to visible white stains
on surfaces but are normally harmless. However, in extreme cases, crystallisation
may take place within the brick causing internal stresses and leading to spalling and
cracking (Hendry et al., 1997).
Sulphate action occurs when water carries sulphate from bricks into mortar,
containing tricalcium aluminate, one of the constituents of Portland cement and
hydraulic lime. This reaction causes mortar to expand, causing cracking or spalling
of mortar joints and occasionally spalling of facing bricks. Hendry (1981) suggested
a limit for sodium sulphate content in bricks, which should not exceed 3% by weight
of a brick in order to avoid spalling and disruption of bricks surface.
2.7 Density
Raw materials and manufacturing process affects bricks density, which could
vary between 1300 kg/m3 to 2200 kg/m3. The density of bricks influences the weight
of walls and the variation in weight have implications on structural, acoustical and
thermal design of the wall. Incorrect assumptions on wall weight can result in
inaccurate dead loads and seismic loads, reduced factor of safety in shear walls and
overestimate of acoustical transmission loss (Grimm, 1996)
25
For acoustical design the sound resistance of a solid masonry wall is related
principally to its weight; the heavier the wall the less is the noise transmitted through
it. Typical sound insulation values for a 102.5 mm and 215 mm thick wall is shown
in Table 2.5. Loudness of 45 dB – 50 dB is considered as moderate loudness
suitable for average home and general office (Drysdale et al., 1994).
Table 2.5: Typical sound insulation values of masonry walls
(Curtin et al., 1995) Material and construction Thickness
(mm) Weight (kg/m2)
Approximate sound reduction index (dB)
Brick wall plastered both sides with a minimum of 12.5 mm thick plaster
215
415
49.5
Brick wall plastered both sides with a minimum of 12.5 mm thick plaster
102.5 220 46
In most existing standards for clay bricks density was not included as
requirements for standardisations. However, in the recent European Standard prEN
771-1: Specifications for clay masonry units, requirements for density should be
declared by the manufacturer for acoustic purposes. The specified tolerances for
density of test samples are graded as D1 and D2 with difference of ± 10% and ± 5%
respectively from the manufacturer’s declared values. The declared values may also
be intended for the calculation of load assumptions and thermal insulation.
One of the main functions of a wall is to provide some degree of thermal
insulation between the exterior and interior environments. Thermal considerations
for buildings include the comfort of users and the energy requirements of heating
and air conditioning equipment. Brickwork has relatively low resistance to thermal
effects, which means that brick is a good conductor of heat. Thermal resistance of
wall increases with the decrease in the density of the materials; hence, a wall’s
thermal resistance is increased by using bricks made of less dense or aerated
materials.
26
However, brick as a high mass building material has the inherent energy
saving features of thermal storage, which means that they are slow to heat up and
slow to cool down. This thermal inertia or thermal storage of brickwork is affected
considerably by its mass, which depended on the density of brick and therefore its
importance in the design load for both heating and cooling.
2.8 Bricks Specifications in International Standards
This section deals with the comparisons of bricks specifications for existing
standards, namely, British Standard (BS), American Standard (ASTM), Australian /
New Zealand Standard (AS/NZS), European Standard (EN) and Singapore Standard
(SS). Malaysian Standard (MS), which is adopted from the earlier version of the
British Standard, was also reviewed. The comparisons is aimed at developing a
better understanding on the way each parameter is being treated for standardisations
in accordance to a particular country’s requirements.
2.8.1 Compressive Strengths
The British Standard (BS 3921:1985) categorised compressive strengths into
classes of Engineering A and B (Table 2.6). These classifications of bricks are
commonly used for construction with aesthetics and strength requirements. All other
bricks and the damp proof-course bricks should have strengths not less than 5
N/mm2, however, the damp-proof course is divided into 2 in accordance to water
absorption.
27
Table 2.6: Classification of bricks by compressive strength and water
absorption (BS 3921:1985) Class Average compressive
strength (N/mm2) Water absorption (5-hr.
boiling) % by weight
Engineering A Engineering B Damp-proof course 1 Damp-proof course 2 All others
≥ 70 ≥ 50 ≥ 5 ≥ 5 ≥ 5
≤ 4.5 ≤ 7.0
≤ 4.5 ≤ 7.0
No limits
In the American Standards (ASTM), compressive strengths are classified in
accordance to the different grades of weathering and exposure conditions as
indicated in Table 2.7. The grades of weathering can be either negligible (NW),
moderate (MW) or severe (SW) depending on the map zoning as given in ASTM.
Table 2.7: Physical requirements for building bricks (ASTM C 62-
89a, 1990) Designation Minimum compressive
strengths brick flat wise lb/in2 (N/mm2)
Maximum water absorption (5-hr. boiling), %
Maximum saturation coefficient
Average of 5 bricks
Individual Average of 5 bricks
Individual Average of 5 bricks
Individual Grade SW 3000(20.7) 2500(17.2) 17.0 20.0 0.78 0.80
Grade MW 2500(17.2) 2200(15.2) 22.0 25.0 0.88 0.90
Grade NW 1500(10.3) 1250(8.6) No limit No limit No Limit No limit
Similar requirements of compressive strengths are given for Facing (ASTM
C 216 – 90a) and Hollow Bricks(ASTM C 652 – 89a) in the category of Grade SW
and MW. However, there is no category for Grade NW in both Facing and Hollow
Bricks.
In the Australian Standard (AS 1225 – 1984) the characteristics compressive
strength is specified, against values for the ratio of manufacturing height to
manufacturing width (Table 2.8).
28
Table 2.8: Characteristic compressive strength in accordance to
Australian Standard (AS 1225:1984) Ratio of manufacturing height to manufacturing width
Characteristics compressive strength, MPa
≤0.7 ≥2
7.0 5.0
In Singapore Standard (SS 103:1974) compressive strengths are classified as
First, Second and Third Grade with minimum compressive strength of 35 N/mm2, 20
N/mm2 and 5.2 N/ mm2 respectively.
It can be seen from the comparisons that the British Standard specified
stringent limits than the ASTM. A minimum compressive strength of 70 and 50
N/mm2 respectively for Engineering A and B was specified in the British Standard.
Whereas, in ASTM the minimum compressive strength specified for structural
facing bricks were 20.7 and 17.2 N/mm2 for Grade SW and MW bricks respectively.
On the other hand, the minimum specification for building bricks in ASTM for
structural or non structural use is higher, i.e. a minimum value of 10.3 N/mm2. The
BS specifies a value of 5 N/mm2. Likewise, a stringent water absorption limit of
minimum 4.5% was found in BS compared to a minimum of 17% in ASTM.
2.8.2 Water Absorption
The BS 3921:1985 defines the limits of water absorption in order to
categorise engineering bricks and bricks for damp-proof course (Table 2.6). The
standard specifies a low water absorption ( ≤ 4.5 %) to classify Engineering A bricks
and bricks for damp-proof course 1; higher water absorption ( ≤ 7.0 %) to classify
Engineering B bricks and bricks for damp-proof course 2. There is no limit of water
absorption for all other types of bricks.
Similarly, ASTM relates compressive strengths to water absorption but with
an additional parameter, the saturation coefficient (Table 2.7). However, the water
29
absorption limits in ASTM were less stringent than the BS. The limits given for the
designation of SW and MW are equal for all three types of bricks: Building, Facing
and Hollow. The maximum water absorption limits are given for the average of five
bricks and for individual bricks. For SW bricks the maximum water absorption
specified are 17 % while the MW bricks are 22 %. No water absorption limits are
required for the grade NW bricks.
On the contrarily, the Australian Standard (AS 1225 – 1984) which was set
up as a basic standard specifies the properties common to most bricks and put no
limit to the water absorption properties as well as the initial rate of suction.
However, it was mentioned in the standard that if the need arises such requirements
should be provided by the purchasers.
Singapore standard (SS 103:1974) specifies some general requirements for
water absorption. The water absorption is limited to 25 % for common bricks, and
no requirement is set for facing bricks. This is probably due to the reason that
brickwork being widely used as infill walls there, which do not require structural or
facing bricks and therefore the water absorption is not critical.
On similar trend with the Australian Standard, water absorption was not
considered as a basic requirement for product description and designation in
European Standard prEN 771-1. Requirements for water absorption will depend on
its relevance in construction and in this case, the limits are to be declared by the
manufacturers.
2.8.3 Initial Rate of Suction (IRS)
British Standard BS 3921:1985 does not specify any limit for IRS. However,
a test method for determining this value is included in Appendix H of the standard.
30
ASTM specified that bricks to be tested for IRS, if the value exceeded
1.5 kg/ m2.min in which case for applications, bricks are to be wetted. The European
Standard prEN 771-1 does not specify any limits for IRS but these values will have
to be declared by manufacturers when relevant to the uses for which the unit is put
on the market. The mean IRS of the sample tested should fall within the range of the
declared values.
The Australian Standard does not specify any requirements for IRS, however
a test method to determine IRS is provided in AS/NZS 4456. Singapore Standard
SS 103:1974 and Malaysian Standard MS 76:1972 specifies no requirement at all on
IRS since both standards were developed using BS 3921:1969 as reference whereby
the initial rate of suction was not accounted for.
2.8.4 Dimensional Tolerance
Sizes and tolerance specified by the British Standard BS 3921:1985 are
meant only for the 225 mm × 112.5 mm × 75 mm format bricks. Requirements for
other bricks format are given in separate standards such as BS 4729(special shapes).
In BS 3921:1985, dimensional tolerance is measured by the deviations in the
overall length, width and height based on 24 bricks (Table 2.9). In addition,
individual brick dimension should not exceed the coordinating size for length, width
and height. Coordinating size is the work size including the allowance for mortar
joints and tolerances and work size is the manufactured size. The overall
measurement is based on the expectation that individual brick dimension should not
differ from the work size by more than 6.4 mm for length whilst 4.0 mm for both
width and height.
31
Table 2.9: Dimensional tolerance based on measurement of 24 bricks
and coordinating and work size in accordance to British
Standard (BS 3921:1985) Coordinating size
Work size Overall measurement of 24 bricks
mm 225 112.5 75
mm 215 102.5 65
Maximum (mm) 5235 2505 1605
Minimum (mm) 5085 2415 1515
Dimensional variations are used in the Australian Standard (AS 125 – 1984)
to classify the categories of bricks. The categories are as follows:
ST0 – bricks not required to be precise in dimensions
ST2 – bricks manufactured to finer tolerances for special applications.
ST3 – bricks where regularity in size is necessary
Limits in dimensional tolerance (Table 2.10) for each of these categories are
based on the variations of length, width and height of 20 bricks for the respective
dimensions. In addition, the length shall not be less than 1.5 times the width or not
exceeding 390 mm. The height shall not be greater than 70 percent of the length.
Table 2.10: Dimensional tolerance in accordance to Australian
Standard (AS 1225 – 1984)
Dimensional tolerance of 20 bricks Size Category
Length
Width Height
ST0 ST2 ST3
± 90 mm ± 40 mm ± 60 mm
± 50 mm ± 25 mm ± 40 mm
± 50mm ± 25 mm ± 40 mm
General criteria for dimensions and proportions (a) Length not less than 1.5 times width nor more than 390mm (b) Height shall not be greater than 70 percent of length.
Tolerance on dimensions specified by ASTM is based on a sample of 10
bricks and each brick should not lie outside the tolerance limits given in the
respective standards for Facing, Hollow and Building bricks. Table 2.11 shows the
tolerance limits for facing bricks. Unlike the British Standard, variations in
32
dimensions are not given in terms of length, width and height but are specified with
respect to some intervals of dimensions. Dimensional variations for facing and
hollow bricks are classified into categories defined by usage, exposure and
architectural requirements corresponding to Type FBX and FBS. In addition, the
facing and hollow bricks are also required to satisfy the tolerances on distortion and
out of square.
Table 2.11: Dimensional tolerance of facing bricks in
accordance to ASTM C 216-90a (1990) Maximum permissible variation from specified dimension, plus or minus (mm)
Specified dimensions, (mm)
Type FBX Type FBS
76 and under 76 to 102, incl. 102 to 152, incl. 152 to 203, incl. 203 to 305, incl. 305 to 406, incl.
1.6 2.4 3.2 4.0 5.6 7.1
2.4 3.2 4.7 6.4 7.9 9.5
Note: FBX: Brick for general use in exposed exterior and interior walls where a high degree of mechanical perfection, narrow colour range and minimum permissible variation in size are required. FBS: Brick for general use in exposed exterior and interior masonry walls where wider colour ranges and greater variation in sizes are permitted than are specified for type FBX.
In European Standard prEN 771-1, the dimensional tolerances are specified
under three categories i.e. T1, T2 and T0 and the respective tolerances for each
category are to be computed using the formula, which depends on the work size
dimensions (Table 2.12). The mean values for all dimensions i.e. the length, width
and height in a sample of 10 bricks should not exceed the declared values by the
respective tolerance in the category. In addition, for works, which require acoustical
property, dimensional tolerance in terms of the range values from a measurement of
10 bricks in a sample should be within the categories given in Table 2.13.
33
Table 2.12: Dimensional tolerance for mean value of work size in
accordance to European Standard (prEN 771-1, 2000) Category Tolerance
T1 0.40 (work size dimension) mm or 3mm whichever is greater±
T2 0.25 (work size dimension) mm or 2mm whichever is greater±
T0 A deviation in mm declared by the manufacturer
Table 2.13: Dimensional tolerance for range of work size in
accordance to European Standard (prEN 771-1) Category Maximum range
R1 0.6 (work size dimension) mm
R2 0.3 (work size dimension) mm
R0
A range in mm declared by the manufacturer
In Singapore Standard (SS 103: 1974) the dimensional tolerance are
categorised as First, Second and Third Grade in accordance to the dimensional
deviations of the overall measurements of length, width and height of 24 bricks
respectively (Table 2.14).
Table 2.14: Classification of bricks in accordance to dimensional deviation
limits in Singapore Standard (SS 103: 1974)
Overall measurements of 24 bricks (mm)
First Grade Second Grade Third Grade
Length 5085 to 5235 5280 to 5472 Width 2415 to 2505 2445 to 2580
Height 1530 to 1620 1704 to 1800
Bricks satisfying all other requirements but having dimensions and compressive strength outside First Grade and Second Grade.
34
2.8.5 Efflorescence
In the British Standard, the levels of efflorescence of bricks are categorised
either as slight, moderate and heavy (Table 2.15). Bricks showing efflorescence in
the heavy category is considered as not complying with the standard. An evaluation
for efflorescence is based on the visual examination of 10 specimens in a sample,
tested in accordance to Appendix C of BS 3921:1985. Slight efflorescence refers to
bricks with up to 10 % of its surface area contaminated with salts and more than 10
% but not exceeding 50 % are categorised as moderate whilst heavy category refers
to bricks with more than 50 % of its surface area affected. In addition, the heavy
category of efflorescence is accompanied by powdering and flaking of the surface.
Table 2.15: Levels of efflorescence in British Standard (BS3921: 1985) Nil No perceptible deposit of salt
Slight Up to 10% of the area of the face covered with a deposit of salt, but
unaccompanied by powdering or flaking of the surface.
Moderate More than 10% but not more than 50% of the area of the face covered with a deposit of salts but unaccompanied by powdering or flaking of the surface.
Heavy More than 50% of the area of the face covered with a deposit of salts and/or powdering or flaking of the surface.
In ASTM requirements for efflorescence is meant only for facing and hollow
bricks. The test method and rating based on 5 pairs of bricks are given in ASTM C
67 – 90a. The bricks are rated as effloresced if perceptible differences are noted and
otherwise. The standard requires bricks of rating not effloresced.
In the Australian Standard (AS 1225 – 1984) the level of efflorescence for
brickwork constructed for appearance should not exceed the limits defined by the
slight category (Table 2.16). The classification is based on the worst case of
efflorescence category occurring in the 5 pairs of bricks tested.
35
Table 2.16: Levels of efflorescence for the Australian Standard
(AS 1225 – 1984)
Nil No observable efflorescence
Slight Not more than 10% of the total external above-water surface covered by a deposit of salts.
Moderate More than 10% of one external above-water surface but not more than 50% of the total external above-water surface covered by a deposit of salts.
Heavy A deposit of salts covering more than 50% of the total external above-water surface.
Severe Any efflorescence that is accompanied by powdering or flaking of the surface of the specimen.
The Singapore standard specifies level of efflorescence similar to the British
standard, however with the addition of another category designated, ‘Serious’. This
level refers to cases where a heavy deposit of salts, accompanied by powdering
and/or flaking of the surface and tending to increase with repeated wetting of the
specimen. Facing bricks and common bricks should not exceed the conditions stated
for slight and the moderate efflorescence (Table 2.17).
Table 2.17: Levels of efflorescence in Singapore Standard
(SS 103:1974) Nil No perceptible deposit of salt
Slight Not more than 10% of the area of the face covered with a
thin deposit of salt.
Moderate A heavier deposit than ‘slight’ and covering up to 50% of the face, but unaccompanied by powdering or flaking of the surface.
Heavy A heavy deposit of salts covering 50% or more of the area of the face but unaccompanied by powdering or flaking of the surface.
Serious A heavy deposit of salts accompanied by powdering and/or flaking of the surface and tending to increase with repeated wettings of the specimen.
36
2.8.6 Soluble Salt Content
In the British Standard (BS 3921:1985) bricks are classified as Low (L) and
Normal (N) indicated by the salt content. The normal category (N) assumes no limit
on soluble salt content while the low category (L) should have salt content not
exceeding the values given in Table 2.18.
Table 2.18: Maximum salt content for the low category (L)
in accordance to British Standard (BS 3921:1985) Soluble salts Maximum content %
Sulphate Calcium Magnesium Potassium Sodium
0.5 0.3 0.03 0.03 0.03
The Singapore Standard (SS 103:1974) specifies a total salt content of 1%
and 2% for Facing and Common bricks respectively. In addition, the Standard also
specifies the content of sulphuric anhydride (SO3), which should not exceed 0.3%
by mass for all the three grades of bricks classifications.
The Australian standard (AS 1225 - 1984) and the ASTM do not include any
requirements for soluble salt content. However, a test to determine the resistance of
bricks to salt attack is given in the Australian Standard, AS/NZS 4456.10:1997. In
this test, specimens are subjected to cycles of soaking in salt solution, oven drying
and cooling. The specimens are then weighed to determine the total mass lost and
this is used to define the salt attack resistance categories i.e. exposure, general
purpose and protected.
The recent European Standard prEN 771-1 designate soluble salt content in
bricks in terms of category of application i.e. S0, S1 and S2 as shown in Table 2.19.
S0 is suitable for completely dry applications, S1 is for normal exposure condition
and S2 is meant for masonry structures subjected to prolonged saturation. There is
no requirement for salt limits in the S0 category of application. An example of such
37
application is in rendered walls where protection from water and moisture
penetration is provided by the layer of plaster applied on bricks surfaces.
Table 2.19: Soluble salt content categories in accordance to
European Standard (prEN 771-1) Total % by mass not greater than Category
Na+ + K+ Mg 2+
S 0 No requirement No requirement
S 1 0.17 0.08
S 2 0.06 0.03
There is no limit given by the pr EN 771-1 on the sulphate content and it was
noted in the standard that consideration on this may be dealt with in national design
codes. There is no requirement for calcium and potassium and sodium is given in
combined form.
2.9 Tests Methods and Measurements in International Standards
2.9.1 Methods of Sampling for Tests in International Standards
Bricks to be tested are to be selected at random from a lot. A lot consists of
the whole population of bricks to be tested. The bricks selected from the lot would
constitute the samples, which are representative of the bricks population. Methods of
sampling and sample size i.e. the number of bricks in a sample could vary from one
standard to another. American Standard specifies the lot size for samples (for the
compressive strength and absorption determinations) as 250,000 brick. For larger
lots 5 bricks are to be selected from each 500,000 brick. The British Standard
limited the lot size as not greater than 15,000 bricks. The lot size was not specified
exactly in the Australian Standard (AS/NZS 4456.1:1997). It states that:
For testing a lot, the sample shall comprise masonry units selected
as representative from an identifiable lot and the test results shall
apply to that lot.
38
The sample size required for the various tests differs according to the
standard requirements as illustrated in Table 2.20.
Table 2.20: Sample size for tests in international standards
Number of bricks required for tests in standards
Tests
BS 3921 ASTM AS/NZS
4456
SS 103 PrEN 771-1
Compressive strength 10 5 10 10 10
Cumulative dimensions 24 - 20 24 -
Individual dimensions 24 10 20 24 10
Water absorption 10 5 10 10 10
Initial rate of suction - 5 10 - 10
Efflorescence 10 10 10 10 -
Salts content 10 - - 10 10
Density - - 5 - 10
The British Standard adopts a larger number of sample size for dimensional
tests whilst the number of bricks were kept to 10 for testing other parameters. The
Singapore Standard and Malaysian Standard were derivations from British Standard,
therefore similarity in the number of bricks used in the respective tests. The ASTM
and Australian/New Zealand Standard are based on metrics, therefore sampling was
based on 5 and 10 units respectively. The European Standard is more consistent in
that all tests are restricted to 10 bricks.
2.9.2 Compressive Strengths
The Compression tests used for determining the brick compressive strength
are carried out differently for various standards (Table 2.22). For example, the
packing materials used are different for test conducted in accordance to BS and
ASTM. Whilst the BS used plywood, the ASTM favours the use of hard capping
made of gypsum and sulphur. Conversely, the European Standard requires bricks
surfaces to be grounded to parallel tolerance before testing.
39
The rate of loading applied to the bricks differ in each standard, and could
vary throughout each test, except for AS/NZS, which adopt a constant loading
method.
The calculation of compressive strength also differs among the standards. BS
3921, ASTM C67 and SS 103 based their calculation on gross area. On the other
hand, AS/NZS 4456 compute the compressive strength based on net area, which
gives a higher value of compressive strength compared to calculation using net area.
In general, the ASTM implement an entirely different test approach
including the number of specimens, curing condition and capping material in
comparison to others.
2.9.3 Water Absorption
Table 2.23 shows the comparisons of the test and measurement methods used
in determining the water absorption of bricks in the various standards. British and
Singapore Standard only adopted the 5-hours boiling test, whereas ASTM specified
both the 5-hours boiling and the immersion tests. These two tests are required for the
determination of the saturation coefficient, which is the ratio of absorption by 24-hr
immersion in cold water to that of the 5-hr boling.
The Malaysian Standard MS 76:1972 allows two alternative methods to
measure water absorption i.e. the 5-hours and the vacuum method, which is similar
to the earlier version of the British standard. However, in BS 3921:1985 only the 5-
hours boiling test is specified since research has shown that there is no simple
relationship between these two methods and results of the two tests could be
different.
The European standard prEn 771-1 specifies the 24-hr water immersion test
to determine water absorption. Water absorption measured by the 24 hr immersion
40
would apparently show a lower value of water absorption in comparison with the 5-
hr. boiling test.
A new method of test for water absorption was introduced recently (Khalaf
and DeVenny, 2002). In this test, 20 mm-brick lumps instead of full brick units were
used. Table 2.21 shows the comparison of results between whole brick and the 20-
mm brick lump for the 24-hr cold immersion and the 5-hr. boiling tests. The results
showed that the5-hrs boiling test underestimates the absorption of bricks. In
addition, results for the 5-hr boiling test were almost equivalent to the 24-hr cold
immersion for the brick lump and in this respect; the saturation coefficient could not
be measured. However, it should be noted that the test for cold immersion was
carried out after bricks were vacuum. The advantage of this new test is that it could
be conveniently carried out without the necessity of big tanks for boiling of whole
bricks and thus saving on the fuel consumption.
Table 2.21: Comparison of water absorption from 5-hr boiling and the
24-hr cold immersion tests using whole brick and brick lumps
(Khalaf and DeVenny, 2002)
Brick type
Water absorption of brick units BS 3921 (5-hr boil) (%)
Water absorption of brick units (24-hr cold) (%)
Water absorption of brick lumps (5-hr boil) (%)
Water absorption of brick lumps (24-hr cold) (%)
Class B Engineering
6.0 5.2 6.3 6.2
Clay 10-hole 6.2 4.6 7.4 7.2
Clay 3 slot and 8 hole
5.8 5.3 7.4 7.4
Clay frogged common
12.9 10.3 14.1 11.5
Granite 2.63 2.55 2.63 2.55
Besides implementing the different types of test for the measurement of
water absorption there are also some differences observed in the number of bricks
used and preparation of specimens before testing. ASTM requires five half-brick
while AS/NZS and BS specify the use of 10 whole bricks. Another difference is in
the duration for attaining constant mass when drying bricks in the oven. BS 3921
41
assumes 48 hours of heating in the oven to achieve constant mass whereas the
AS/NZS and ASTM monitor the weight loss during drying and constant mass is
assumed if subsequent drying indicate that the change in mass is not greater than
0.1 % of the previous weight for the AS/NZS and 0.2 % for ASTM.
2.9.4 Initial Rate of Suction
Table 2.24 shows the comparisons of test and measurement methods for the
initial rate of suction as required by the various standards. The tests principles are
similar in all standards, whereby bricks capillary suction is measured by immersing
bricks in about 3 mm depth of water for a duration of 1 minute. The ASTM and the
Australian Standard specify some means to set up the apparatus in maintaining water
level to the required height of immersion.
In the Australian / New Zealand Standard (AS/NZS 4456:1997) IRS are
given in terms of Anet and Agross as shown in Table 2.24. The ASTM specified that
the IRS measured for cored bricks should be modified with a factor depending on
the net area of immersion, which will result in a higher value of IRS compared with
calculation based on gross area. The BS on the other hand based its IRS calculation
on the gross area of immersion.
2.9.5 Dimensional Tolerance
Methods of testing to determine dimensional tolerances vary between the
standards (Table 2.25). British, Australian/New Zealand, Malaysian and Singapore
standard specify dimensional tolerance measured from the cumulative dimensions of
specified numbers of bricks, whereas, ASTM and European standard specify an
individual brick dimensional tolerance. Other variations include the numbers of
bricks required for the cumulative dimensions and the methods of measuring the
tolerance.
42
ASTM based their tolerance on a sample of 10 bricks and each brick should
not depart from the specified size by more than the tolerance given in the standard.
While, the British and Singapore standard establish the tolerance limits based on two
approaches namely (i) individual dimension (ii) the overall measurement for 24
bricks. While AS/NZS, tolerance limit is based on overall measurement of 20 bricks.
The European standard specifies an entirely different dimensional tolerance
limit based on the mean and range values for a sample of 10 bricks according to the
different categories. The mean deviation refers to basic requirement and constitute a
minimum description of a unit whilst the range is only required when relevant to the
needs of application. In addition, European standard also specified some geometry
requirements for bricks to be used in elements subjected to acoustics requirements.
2.9.6 Efflorescence
The test for efflorescence in existing standards involved cycles of wetting
and drying of bricks in laboratory after which they are examined for the salts
depositions on the surface. The procedures for quantifying efflorescence differ
between the standards (Table 2.26). British standard and Australian/New Zealand
standard categorise efflorescence into levels in accordance to the degree of
contaminants. In contrast, the ASTM quantify efflorescence in bricks either simply
effloresced or not effloresced. The new amendments made to BS 3921 in 1995
ignored the effects of efflorescence. Similarly, European Standard prEN 771-1 does
not specify any requirement for efflorescence in bricks.
43
Table 2.22: Test methods and measurements for compressive strength in international standards
Test Standards
Sample size
Preparation of specimen Speed of testing Capping material Compressive strength
calculations
BS 3921 Appendix. D
10 (Whole brick)
Immerse brick in water for 24 hrs or saturate by boiling
Convenient rate not exceeding 35 N/(mm2.min) until half of expected max. load after that reduces to 15 N/(mm2.min) until failure.
Soft capping: three-ply 4mm thick plywood
Maximum load
smaller bed of the overall dimension
ASTM C67-90a
5 (Half brick)
Dry specimen in the oven for not less than 24 hrs.
Convenient rate until about half of expected maximum load after that uniform rate.
Hard capping: • Gypsum • Sulphur
Maximum load
Average of gross area of upper and lower bearing surfaces
AS/NZ 4456:1997
10 (Whole bricks)
Moisture content as sampled
Constant rate within a range equivalent to a stress of 150 kPa/s (9 N/mm2.min) to 700 kPa/s (42 N//mm2.min)
Soft capping: • 4 -6 mm plywood • 12mm fibreboard
Unconfined 1000a
PC KA
=
where, aK = aspect ratio factor A = net area
PrEN 771 – 1
10 (Whole bricks)
Bricks tested dry Not available No capping needed. Surfaces ground to a parallel tolerance
Not available
44
Table 2.23: Test methods and measurements for water absorption in international standards
Test Standards
Sample size
Type of test Determination of dry mass Test procedures Calculation of water absorption
BS 3921 Appendix. E /SS 103
10 (Whole brick)
5-hour boiling test
Drying – in oven (110 ±8°C) for at least 48 h. Cooling – bricks left unstacked in a ventilated room for 4 h, with 2 h of continuous air using an electric fan. Dry mass is determined when bricks are cool.
5-hr.boiling – Bricks are boiled in a tank of water for 5 hrs. Then are cooled naturally in the water for not less than 16 hours nor more than 19hrs.Then take the weight (wet mass).
(wet mass-dry mass)100
dry mass%
Average of 10 specimens to the nearest 0.1%.
ASTM C67-90a
5 (Half brick)
i) 5-hour boiling and ii) 24-hour immersion test.
Drying – in oven (110 to 115°C for not less than 24 h and until two successive weighing at intervals of 2 hrs. show an increment of loss not greater than 0.2% of previous weight. Cooling – in a room temperature maintained at 24 ± 8°C, relative humidity 30 – 70%. Record the average dry mass of all specimens as Wd.
Immersion test – submerge cool bricks in clean water at 15.5-30°C, for 24 h. Then remove specimens wipe dry and weigh. Record the average weight of all specimens as Wsc. 5-hr.boiling – bricks are boiled in a tank of water for 5 hrs. Then cool naturally to 15.5-30°C. After that remove specimens wipe dry and weigh. Record the average weight of all specimens as Wsb.
Absorption by immersion: =(Wsc-Wd)/ Wd Absorption by boiling: =(Wsb-Wd)/ Wd (Saturation coeff. = absorption by immersion / absorption by boiling)
AS/NZ 4456.14: 1997
10 (Whole bricks)
i) 5-hour boiling and ii) 24-hour immersion test.
Drying – in oven (110 ±8°C) until consecutive weighing at intervals of 4 hrs show a change in mass of not greater than 0.1 %. Record the lowest average weight for all specimens at room temperature as the dry mass m1.
Immersion test – submerge cool bricks in clean water at ambient temperature, for 24 h. Then remove specimen wipe dry and record the average mass of all specimens as m2. 5-hr boiling – bricks are boiled in a tank of water for 5 hrs. Then cool naturally to 15.5-30°C. Then take this saturated weight and record the average mass of all specimens as m3.
Absorption by immersion: Wi (%) = 100(m2-m1)/ m1 Absorption by boiling: Wb (%) = 100(m3-m1)/ m1 Saturation coefficient = Wi / Wb
prEN 771 - 1 10 (Whole bricks)
24-hour immersion test.
Not available Not available Not available
45
Table 2.24: Test methods and measurements for initial rate of suction in international standards
Test Standards
Sample size Preparation of specimen Test procedures Initial rate of suction calculations
BS 3921 Appendix. H
Not specified
The bricks are dried in the oven as in absorption test. The weight of the dry brick is recorded as
1m in gm.
The dry brick is immersed in water at a depth of 3 ± 1mm for 1 min. Record this weight 2m in gm.
22 1
2
1000( ) in kg/m .min .
where = gross area of the immersed face of the brick in mm
m mIRS
AA
−=
ASTM C67-90a
5 (Whole brick)
i) Oven drying as in absorption test or ii) Ambient air drying The weight of the dry brick is recorded as 1m in gm.
The dry brick is immersed in water at a depth of 3 ± 1mm for 1 min. Record this weight as
2m in gm. Some means of maintaining water level at a depth of immersion of 3 ± 1mm is provided in the standard.
IRS = 1 2m m− in gm. IRS is measured in gm/min/30 in2. For cored bricks the measurement of IRS i.e. 1 2m m− has to be multiplied
with a factor of 30net area
.
AS/NZS 4456.17: 1997
10 (Whole brick)
Bricks are dried in the oven as in absorption test. The weight of the dry brick is recorded as 1m in gm.
The dry brick is immersed in water at a depth of 3 ± 1mm for 60 ±1 sec. Record this weight
2m in gm. A set up of the apparatus suggesting a way of maintaining immersion at depth of 3 ± 1mm is provided in the standard.
2 1
2 1
1000( )
1000( )
grossgross
netnet
m mIRS
Am m
IRSA
−=
−=
IRS (kg/m2 .min) for each brick and mean of the 10 specimens.
prEN 771 - 1 10 (Whole bricks)
Not available
46
Table 2.25: Test methods and measurements for dimensional tolerance in international standards
Measurement of dimensional tolerance Test Standards Individual brick dimension Cumulative (overall dimension)
BS 3921 Appendix. A
1. Each brick from the 24 bricks for the cumulative measurements must not exceed the coordinating size as given in Table 2.9.
1. Cumulative dimensions of 24 bricks must not exceed the specified range for length width and height as indicated in Table 2.9. The cumulative measuremen is based on the assumption that each brick should not differ from the work size by more than 6.4mm for length, 4mm for width and height.
ASTM C67-90a
1. Each brick from the 10 bricks in a sample should not vary from the specified allowable dimensional tolerance as given in Table 2.8
2. Tolerance on distortion and out
of square is also specified for facing bricks.
No cumulative dimension specified
AS/NZS 4456.17: 1997
1. Each brick from the 20 bricks should
comply with the general criteria as given in Table 2.7.
1. Cumulative dimensions of 20 bricks must not exceed the specified range for length width and height for the three categories (Table 2.10). These categories identify bricks tolerance requirements: ST0 – bricks no required to be precise in dimensions ST2 – bricks manufactured to finer tolerance for special application ST3 – bricks where regularity in size is necessary.
47
Table 2.25 (cont.): Test methods and measurements for dimensional tolerance in international standards
Measurement of dimensional tolerance Test Standards
Individual brick dimension Cumulative (overall dimension)
PrEn 771-1 1. Mean dimensions for the test sample should not be greater than declared means for categories T1, T2 and T0
Where,
T1: 0.40 (work size dimensions) mm or 3 mm whichever is greater±
T2: 0.25 (work size dimensions) mm or 2 mm whichever is greater± T0: a deviation in mm declared by the manufacturer.
2. The declared range should be within the range determined within the test sample for the categories R1, R2 and R0
Where, R1: 0.60 (work size dimensions) mm±
R2: 0.30 (work size dimensions) mm± R0: a range in mm declared by the manufacturer.
No cumulative dimension specified
48
Table 2.26: Test methods and measurements for efflorescence in international standards
Test Standards
Specimen Numbers Test procedures
Measurements of efflorescence
BS 3921 Appendix. C *
10 (Whole brick)
One face of the brick is subjected to 2 cycles of wetting and drying for the specified time. Then examined for efflorescence by comparing this face with the other faces that is not subjected to the wetting and drying cycles.
Levels for efflorescence as shown in Table 2.7. Bricks are categorised according to the worst occurrence. Bricks with ‘Heavy’ efflorescence are considered as not complying with the standard.
ASTM C67-90a
5 pairs (Whole brick)
One specimen from each pair is allowed to stand on ends partially immersed in water for 7 days. The other pair is kept in a room with specified humidity and temperature. Then dry both sets in oven for 24 hrs. After that compare and examine both sets for efflorescence.
Efflorescence is recognised as either ‘effloresced’ or ‘not effloresced’
AS/NZS 4456.6: 1997
5 pairs (Whole brick)
One specimen from each pair is allowed to stand on ends partially immersed in water for 7 days then air dry for 2 days. After that compare and assessed with respect to a matching brick.
Levels for efflorescence as shown in Table 2.13. Bricks are categorised according to the worst occurrence. Bricks exposed to view should not exceed ‘slight’.
prEn 771-1
No requirements
*Note: Efflorescence test has been removed from BS 3921 (AMD 8946/December 1995)
49
2.10 Conclusions
A considerable amount of past research and studies on masonry indicated the
relationship between masonry strength and unit strength. An example of such
relationship developed by Hendry (Equation 2.1 and 2.2) and is used in the code for
masonry design (BS 5628:1985). The compressive strength is therefore one of the
most important bricks properties for design requirements, and dealt by
specifications.
The compressive strengths of bricks can vary from 5 N/mm2 to over 100
N/mm2, depending upon materials and types of manufacturing and to some extent
are affected by the methods of testing in evaluating the compressive strength.
Malaysia Standard / British Standard identifies its clay bricks as Engineering A and
B (compressive strength ranging from more than 70 N/mm2 to not less than 50
N/mm2) for structural purposes and as ‘All others’ for strengths above 5 N/mm2. On
the other hand, ASTM classifies bricks into three categories i.e. building, facing and
hollow, with a minimum compressive strength of 20.7 N/mm2 and 17.2 N/mm2 to be
used in regions of severe (SW) and moderate weathering (MW) respectively. Grade
NW bricks with minimum compressive strength of 10.3 N/mm2 is meant for
applications in regions with negligible weathering. Singapore Standard defines
bricks as First, Second and Third Grade in accordance to the levels of compressive
strengths, with a minimum value of 5.2 N/mm2 for general purpose construction.
The methods of testing compressive strength are known to affect the
computed values obtained in standards. The usage of soft capping specified by the
British and Australian/New Zealand Standard is believed to reduce platen restraints.
Platen restraint induces artificial strengthening thereby enhancing the compressive
strength. Hard capping is used in ASTM and European Standard prEN 771-1 uses no
capping material, however requires the surfaces to be ground parallel and free of
irregularities.
The British, ASTM, Malaysian and Singapore standards based the evaluation
of compressive strength upon bricks tested on bed faces with the exception of
Australian/New Zealand, which accommodate the compressive strength for tests in
50
other orientations, producing a different height to thickness ratio (h/t) depending on
the bricks orientation in the tests. The aspect ratio, h/t, has a considerable effect on
the compressive strength, the higher the ratio the least is the compressive strength.
Subsequently, bricks tested on the bed face (lowest h/t ratio) display the largest
compressive strength. The development of European specification for masonry units,
prEN 771-1 introduces similar test methods to Australian/New Zealand Standard,
but the strength limits are to the discretion of the manufacturers declared values. The
EN and Australian approach of defining the unit strength in various orientations
provide a comprehensive information on the unit and this is useful for structural
design purposes.
Amongst others the compressive strength of units are affected by the curing
methods. Previous research; tend to indicate higher strength for dry bricks as high as
15 % greater than cured bricks. Evaluation of compressive strengths by ASTM and
European Standard was based on dry bricks in contrast to British, Malaysian, and
Singapore standards, which cured the bricks by saturating them in cold immersion or
by boiling. On the contrarily, Australian/New Zealand Standard carried out the
compressive strength on bricks as received i.e. the bricks having a moisture content
as sampled. However, if the bricks moisture content exceeds 25 %, air-drying is
required.
Most masonry standards dictate the requirements of water absorption for
bricks with structural applications and cases where resistance to water and moisture
penetration are critical. For example, in British Standard BS 3921: 1985 low water
absorption limits is specified for Engineering A and B and damp-proof course 1 and
2 bricks with water absorption of ≤ 4.5 % and ≤ 7.0 % respectively. Bricks for other
applications than those already mentioned are not restricted to any water absorption
limits. Similarly, masonry specification in ASTM C 62-89a, ASTM C 652-89a and
ASTM C 216-90a specified limits for water absorption of bricks with high levels of
compressive strengths where applications are specifically for severe and moderate
weathering regions. For negligible weathering regions bricks are not required to
conform to any limits of water absorption.
51
The Australian Standard, AS 1225-1984, is a general standard for all
masonry materials and does not specify limits for water absorption however has
included test methods for determining these values. The European Standard for
masonry units (pr EN 771-1), specifies water absorption requirements for bricks to
be used in external applications and the value is as declared by the manufacturers.
Recent research indicated the existence of some relationship between water
absorption to bricks porosity and compressive strength. The research revealed that
bricks with the least water absorption and small porosity produce higher
compressive strengths and this relationship could be used as an early indicator for
compressive strength. Other studies carried out on the relationship of water
absorption and bricks porosity had established durability indices, which provide
guideline for resistance of masonry against the freeze and thaw actions. These
indexes provide limits that can be used to identify durable and non-durable bricks.
The two types of test methods used for measuring water absorption i.e. the 5-
hours boiling and 24-hours cold immersions are known to give different
measurements. The 5 hours boiling test provides results for saturated conditions,
while the 24 hours cold immersion gives partial saturation. The prEN 771-1 requires
water absorption of bricks to be determined by the 24 hours cold immersion test,
hence producing a lower value of water absorption measurement.
The IRS is the rate at which a brick sucks water from mortar during laying
and therefore affects the bond strength between units and mortar. The suction
properties are crucial to the design of walls subjected to lateral load particularly in
highly stressed masonry structures. The IRS does not form an integral part of the
specifications for both the Australian/New Zealand and British Standards. However,
testing method to determine IRS is provided by the standards. On similar grounds
the European standard pr EN 771-1, requires IRS to be specified for relevant cases
of applications and the value of IRS to be declared by the manufacturer. In contrast,
ASTM requires the IRS values for bricks to be known and recommends that bricks
to be wetted before laying if the IRS is higher than 30 g/min per 30 in2 (1.5
kg/min/m2). The practice of wetting bricks before laying ensures proper bond
development between mortar and the highly absorptive bricks. In highly stressed
52
structures a good bond between mortar and bricks is essential to prevent the
occurrence of cracks in mortar joints and thus enhancing the water-tightness
property of facing brickwork.
The dimensions and tolerances of bricks are used to describe and designate
masonry units in standards. Dimensional variations are expected due to the
shrinkages in the natural clay deposits, which take place during drying and burning
processes. The standards specified dimensional tolerances to restrict these variations
in satisfying the required construction criteria. For facing bricks, dimensional
control is more stringent for wall appearance and lesser for other applications. Most
standards specify dimensional tolerances according to the types of masonry
construction.
There are two approaches of measuring dimensional tolerances in standards,
namely the individual and cumulative dimension of a set of bricks. In the recent
European Standard dimensional tolerance are specified in terms of the mean and the
range from a sample of 10 bricks and this should be within the range defined in the
specified categories. The dimensional tolerance determined from cumulative
dimensions of a set of bricks as given by Australian Standard AS 1225:1984,
Malaysian Standard MS 76 Part 2:1972 and British Standard BS 3921:1985 helps to
offset the individual brick dimensional variation, which maybe useful in determining
variation within and between batches of bricks delivered on site.
Efflorescence, that appear on the surfaces of bricks after construction, is
usually not harmful to a masonry structure but unsightly in facing brickwork. These
white stains indicate the presence of soluble salts in bricks. The test method for
efflorescence in all standards involves simple laboratory works and measurements
and evaluations of efflorescence are based on visual inspection. The test seems not
related to the field exposure that a brick is exposed to in a masonry structure.
Furthermore, with the introduction of limits for soluble salt content in all bricks, the
efflorescence requirement was considered as unnecessary and had been omitted by
the British Standard and the new European standard. However, this test is being used
by manufacturers to indicate the soluble salt content in bricks and its liability to
efflorescence.
53
Recent global development in standardisation works particularly in Europe
has brought about some significant changes to masonry standards. The British
Standard, upon which the existing Malaysian standard is based on, will soon be
replaced by the harmonised European Standard prEN 771-1 specifications for
masonry units. The new standard introduces some modifications to the BS 3921,
which include new test methods and requirements criteria, prompted by research
discovery and new technological development in masonry. A study on the
performance of local bricks is therefore timely to provide comprehensive
information on bricks considered relevant to the current construction industry and
market and design requirements pertaining to modern construction.
CHAPTER 3
LABORATORY TESTS ON PHYSICAL
PROPERTIES OF BRICKS
3.1 Introduction
This chapter examines the physical properties of the bricks. Laboratory
investigations were performed on samples of bricks at the Structural Laboratory of
the Faculty of Civil Engineering, Universiti Teknologi Malaysia. Tests were
conducted to examine dimensional tolerance, density, initial rate of suction, water
absorption, compressive strength, soluble salt content and efflorescence.
3.2 Sampling of Bricks
Sampling is a process involving the collection of bricks at random to make
up a sample to represent the population of bricks used in this research. The number
of specimens in a sample i.e. the size of sample (n) is the number of bricks required
for any tests. Sampling was carried out at a brick factory, which is considered a
major producer of brick in the country. The factory has a monthly production
capacity of 10,000,000 units of bricks and it is also a major exporter of bricks to
counties in Asia like Japan and Singapore.
55
Two categories of bricks comprising of the facing brick and the common
brick were sampled at random from the factory output. Facing bricks are quality
bricks with attractive external appearance and common bricks are meant for general
building works that do not require external look. Random selection means that every
brick must have a probability of being selected. However, this was found to be quite
impossible at times when bricks were in big piles making it difficult to reach and
acquired. Four factory visits were made and for each visit a batch of approximately
100 pieces of facing bricks and 40 pieces common bricks were selected. A batch is a
collection of bricks acquired at every visit.
3.3 Testing Programme
The testing programme (Table 3.1) shows the extent of the work detailing the
total number of batches used for the laboratory investigations including the number
of samples in every batch for the various tests. The test procedures and the sample
size (n), i.e. number of bricks required in every sample for testing of dimensional
tolerance of 24 bricks, Initial rate of suction (IRS), absorption, compressive strength,
soluble salt content and efflorescence were generally in accordance to BS 3921:
British Standard Specifications for Clay bricks (1985), with the exception of the
density test which were done with reference to the AS/NZS 4456.8:1997.
The tests were performed in sequence as shown in Figure 3.1, such that it
will optimise the quantity of sample used in the investigation. For example, each test
will commence with dimensional measurements, and the same 10 bricks be tested
for density, IRS, absorption and compression. The fragments from the compressive
strength will then be used for testing of soluble salt content. The efflorescence test
was conducted separately on another 10 bricks from each batch of samples.
The series of tests shown in Figure 3.1 were performed for the facing bricks,
which are referred to as structural bricks. The common bricks were only tested for
their compressive strengths. Structural bricks entailed design calculation which
requires the compressive strengths of units to be known, for this reason, it is
56
essential to examine the strengths characteristics and other physical properties.
Hence, the properties of facing bricks need to be investigated in this case. On the
other hand, common bricks, which are meant for general building works do not
require specification on the properties except for its compressive strength. Thus,
they are only tested for this particular property. Compressive strength test was
carried out on common bricks to examine the variation of strengths in order to
categorise the brick into their strengths classification. Efflorescence, which tends to
affect external appearance may be considered insignificant for common bricks as
they are usually used for infill walls with plastered surfaces. The water absorption
property may also not be considered essential in this case since the plaster may help
in resisting water penetration into a wall to a certain degree.
24 bricks 10 bricks 10 bricks Figure 3.1: Sequence of testing
Dimension Efflorescence
Density
Initial rate of suction
Absorption
Compressive strength
Soluble salt content
57
Table 3.1: Testing programme Number of samples per batch for the various tests
Dimensional tolerance
Bat
ch
Dat
e of
sa
mpl
ing
Num
ber
of
bric
ks
sam
pled
in a
ba
tch Overall
dimension (n = 24)
Individual dimensions (n = 6)
Density (n = 10)
Initial rate of suction (n = 10)
Water Absorption (n = 10)
Compressive strength (n = 10)
Soluble salt content (n = 10)
Efflores- cence (n = 10)
1 26/4/2001 100 facing bricks
2 8
3 3 3 6 2 1
40 common bricks
- - - - - 3 - -
2 13/6/2001 100 facing bricks
4 16 8 8 8 8 3 1
40 common bricks
- - - - - 3 - -
3 25/7/2001 100 facing bricks
4 16 8 8 8 8 4 1
40 common bricks
- - - - - 3 - -
4 19/9/2001 100 facing bricks
4 16 8 8 8 8 3 1
40 common bricks
- - - - - 3 - -
Total samples for all batches 14 56 27 27 27 30 12 12 4
58 3.4 Dimensional Tolerance
Dimensional tolerances were measured from the respective length, width and
height of overall dimension of 24 bricks and individual brick dimension. Tests were
conducted on 24 bricks to examine the dimensional tolerance in accordance to BS
3921. The 24 bricks were selected at random from a batch of 100 bricks. For the
measurement of overall lengths, the bricks were placed in two rows, each of 12
numbers, on a flat surface in the laboratory. Measurements were made using an
inextensible steel tape. The measurements for the two rows were added to give the
overall dimension of length for 24 bricks. Measurements of width and height were
taken for 24 bricks in a row. A long steel channel, aligned against the row of bricks
ensured that bricks were arranged in a straight line (Figure 3.2). For individual
dimensions the vernier calliper were used in which a measurement to two decimal
places was recorded. The results for the overall dimension of length, width and
height are shown in Table 3.2. Table 3.3 shows the individual dimension for length
width and height in the samples. The complete tabulation of results for the
individual dimensions in each specimen is shown in Appendix A1.
Table 3.2: Overall dimensions of 24 bricks
Sample Length (mm)
Width (mm)
Height (mm)
1 5240 2415 1638 Batch
1 2 5254 2410 1646 3 5216 2408 1648 4 5263 2426 1651 5 5241 2421 1650
Batch 2
6 5243 2419 1653 7 5175 2405 1628 8 5218 2412 1640 9 5185 2413 1625
Batch 3
10 5178 2397 1634 11 5203 2416 1638 12 5211 2400 1643 13 5210 2409 1643
Batch 4
14 5213 2414 1644
59 Table 3.3: Individual brick measurement of length, width, and height for all batches
Sample Length (mm) Width (mm) Height (mm)
1 218.43 100.20 67.08 2 218.43 99.79 67.23 3 216.58 99.00 67.45 4 218.03 99.63 67.19 5 216.57 98.96 66.37 6 217.68 99.81 67.16 7 217.68 99.97 67.91
Batch 1
8 219.08 99.91 68.01 9 216.64 99.93 68.18
10 215.53 99.31 67.83 11 216.13 99.33 68.06 12 216.35 98.85 67.67 13 218.01 100.41 68.18 14 217.67 100.27 67.25 15 217.68 99.83 67.67 16 218.82 100.73 68.81 17 216.78 99.77 67.60 18 218.97 100.89 68.95 19 216.66 99.76 68.18 20 217.74 100.22 68.10 21 219.05 100.22 68.08 22 217.49 101.03 68.57 23 216.29 99.81 67.86
Batch 2
24 217.97 99.97 67.89 25 215.74 99.73 67.80 26 214.62 99.53 66.93 27 215.09 99.81 67.09 28 214.67 99.90 67.08 29 215.43 99.67 67.43 30 216.26 100.45 67.67 31 214.71 99.38 67.37 32 215.71 100.27 67.54 33 215.19 99.39 67.35 34 215.45 99.99 67.23 35 215.13 99.03 66.93 36 215.10 98.70 67.05 37 216.06 99.82 67.04 38 214.98 99.22 66.83 39 214.77 99.59 66.96
Batch 3
40 215.18 100.17 67.08 41 216.42 100.23 67.70 42 216.23 99.78 67.53 43 215.63 99.63 67.41 44 215.09 98.89 67.13 45 215.09 98.73 67.28 46 215.69 99.43 67.43 47 215.72 99.13 66.58 48 216.18 99.15 67.58 49 216.92 100.23 67.35 50 214.57 99.01 67.03 51 216.83 100.03 67.53 52 217.00 99.73 67.01 53 215.83 99.96 68.28 54 215.36 99.48 67.19 55 216.14 100.27 67.43
Batch 4
56 216.28 99.80 67.46 Mean x
Std. dev. s 216.42 1.912
99.73 1.116
67.48 0.888
60
(a)
(b)
(c)
Figure 3.2: Overall Measurement of (a) length, (b) width
and (c) height for 24 bricks
61 3.5 Density
The bricks density was measured in accordance to AS/NZS 4456.8, since BS
3921 does not provide for such testing specification. However, this is a new
requirements in the European Standard for which bricks are to be tested. Ten bricks
were selected from the 24 bricks used for dimensional testing. Each brick was
labelled with numbers for example 51, 27, 48…99 (Table 3.4) using permanent
waterproof ink for identifications. The weight of each brick was taken to represent
the ambient mass i.e. the mass at the time of measurement, mo. The bricks were then
immersed in water for 2 hours, then removed from the water and allowed to drain
for not more than 1 min. Any excess water on the surface were then removed by
wiping with a cloth. The brick was then weighed and the mass recorded i.e. m1.
After that, the brick was placed in an apparatus to measure its submerged mass, m2.
These procedures were repeated for all 10 bricks.
The device used to measure submerged mass of bricks throughout the testing
programme is shown in Figure 3.3. This device was an existing unit used previously
for measuring the density of concrete cubes in the laboratory. It consists of a water
bath and an attached steel cage to hold the specimens under investigations. The steel
cage is connected to a digital weight indicator. Upon lowering the cage and
specimen, the readings of submerged mass will be indicated by the digital indicator.
Based on Archimedes principle the submerged mass were used to evaluate the
volume.
Volume was calculated using submerged mass as stated in equation 3.1.
( )1 2(mm ) 1000V m m= − ×3
…(3.1)
Where,
1m = mass of wet brick in gram.
2m = submerged mass of brick in gram.
The volume is then used to calculate the ambient density Da using equation 3.2.
3( ) 1000000 in kg/moa
mDensity DV
= × …(3.2)
62 Where,
om = ambient mass in gram.
An example of the test results for density determined for bricks of Batch 1 is
shown in Table 3.4. A complete tabulation of results for tests carried out throughout
the research is given in Appendix A2.
Table 3.4: Density of bricks for Batch 1 Brick Identification
Ambient mass
0( )m gm.
Mass after 2 hours soaking
1( )m gm.
Immersed mass
2( )m gm.
Volume (V) V=(m1-m2)*1000
mm3
Density (Da) (mo/V)*1,000,000
kg/m3
51 2395 2630 1270 1360000 1761.03 27 2440 2590 1270 1320000 1848.48 48 2400 2620 1270 1350000 1777.78 67 2435 2650 1300 1350000 1803.70 32 2390 2630 1280 1350000 1770.37 6 2395 2600 1260 1340000 1787.31
19 2335 2470 1220 1250000 1868.00 22 2410 2610 1260 1350000 1785.19 50 2475 2690 1310 1380000 1793.48
Sam
ple
1
9 2365 2600 1250 1350000 1751.85 Mean x = 1794.719
Std. dev. s = 37.03036 2435 2690 1300 1390000 1751.80 44 2455 2640 1280 1360000 1805.15 43 2325 2570 1240 1330000 1748.12 64 2460 2670 1300 1370000 1795.62 38 2400 2600 1270 1330000 1804.51 45 2450 2680 1300 1380000 1775.36 62 2455 2670 1300 1370000 1791.97 30 2355 2560 1250 1310000 1797.71 70 2440 2620 1290 1330000 1834.59
Sam
ple
2
66 2430 2630 1280 1350000 1800.00 Mean x = 1790.483 Std. dev. s = 25.923
85 2315 2520 1230 1290000 1794.57 92 2305 2530 1230 1300000 1773.08 41 2390 2680 1250 1430000 1671.33 96 2510 2770 1350 1420000 1767.61 87 2420 2650 1300 1350000 1792.59 43 2385 2680 1290 1390000 1715.83 91 2270 2490 1200 1290000 1759.69 42 2420 2640 1290 1350000 1792.59 81 2465 2690 1330 1360000 1812.50 99 2405 2650 1310 1340000 1794.78
Sam
ple
3
Mean x = 1767.456 Std. dev. s = 43.169
63
Figure 3.3: Apparatus for the measurement of density
3.6 Initial Rate of Suction
The bricks used for density tests were retested for the initial rate of suction.
Initially the bricks were dried in a ventilated oven for two and a half days at a
temperature of 110 °C. In accordance to BS 3921 constant mass is assured if bricks
are subjected to heating at 110 °C for not less than 48 hours. The bricks were
removed from the oven and cool to room temperature for a period of approximately
4 hours. Cooling was assisted by passing air over the bricks using an electric fan for
a period of 2 hours. Upon cooling, the bricks were weighed and the dry mass dm
recorded.
In the tests a large shallow rectangular pan of size 600mm × 600mm giving,
an area of 0.36m2 was used. Two 10mm steel bar were placed at the bottom of the
pan at approximately 100 mm apart, to form a platform for the bricks to rest during
measurement process (Figure 3.4). The steel bar was firstly immersed with water to
a depth of about 3mm. The pre-weighed dry brick was placed on the bar whilst the
water level is closely observed with a measuring gauge to ensure that depth of the
immersion for the brick was maintained at 3 ± 1mm throughout the duration of
immersion, 1 minute. After 1 minute, the brick was removed from the water and
excess water wiped off with a damp cloth. The brick was reweighed and the mass
64
wm recorded. These procedures were repeated for 10 bricks. Some typical results for
Batch 1 are shown in Table 3.5 and others can be found in Appendix A3. The initial
rate of suction due to gross area of immersion (IRSgross), in kg/m2.min is calculated
using equation 3.3a.
1000( )w dgross
gross
m mIRSA
−= …(3.3a)
Where,
dm is the mass of the dry brick in gram.
wm is the mass of the wet brick in gram.
Agross is the gross area of the immersed face of the brick in mm2.
The IRS for net area of immersion (IRSnet) was determined as shown in
equation 3.3b.
1000( )w d
netnet
m mIRSA
−= …(3.3b)
Where,
Anet is the net area of immersion i.e. gross area less the area of perforations.
Precautions were taken so that the limits of immersion remained at 3 ± 1mm
as required by BS 3921. The size of pan used in this testing programme was 0.36m2
in area and this did not cause a significant drop in water level after a subsequent test
was conducted at the immersion limits recommended by BS 3921. The minimum
size of the tank recommended by AS/NZS 4456 is 0.25m2.
The role of the pan size here is not considered very significant, for as long as
the tests were conducted in accordance to the depth of immersion and the duration of
absorption (1 min.). The larger the pan, the smaller the drop in water level and the
less frequent to top up the level to 3 ± 1mm limit. The BS 3921 does not specify the
size of the pan. ASTM C67 specifies that pan should be at least 0.19 m2.
Additionally, the Brick Institute of America through its Technical Note 39,
recommended a pan size of 0.19m2 and observations on bricks with IRS
40g/min./30in.2, equivalent to 2.05 kg/min.m.2, only caused a water level drop of
less than 0.25mm. In this regards, this is hardly measurable.
65
Figure 3.4: Apparatus for measuring the initial rate of suction
Table 3.5: Initial rate of suction in samples for Batch 1
Bri
ck
iden
tific
a Dry mass,
dm (gm)
Wetmass
wm (gm)
Length (mm)
Width (mm)
Immersed area, Agross (mm2)
IRSgross (kg/m2.min)
( )1000 w dm mA−
Immersed area, Anet (mm2)
IRSnet (kg/m2.min)
( )1000 w dm mA−
16 2445 2485 221.15 100.75 22280.86 1.795 18905.86 2.116 2 2390 2420 216.50 98.80 21390.20 1.403 18015.20 1.665
11 2415 2450 218.30 99.70 21764.51 1.608 18389.51 1.903 4 2370 2400 216.05 98.30 21237.72 1.413 17862.72 1.679 9 2435 2485 221.45 102.25 22643.26 2.208 19268.26 2.595
17 2430 2465 220.05 100.75 22170.04 1.579 18795.04 1.862 19 2440 2490 220.10 100.10 22032.01 2.269 18657.01 2.680 3 2435 2455 217.55 98.80 21493.94 0.930 18118.94 1.104 7 2415 2450 217.10 100.00 21710.00 1.612 18335.00 1.909
Sam
ple
1
8 2410 2435 216.60 99.80 21616.68 1.157 18241.68 1.370 1 2380 2410 216.55 99.55 21557.55 1.392 18182.55 1.650
12 2420 2455 217.95 99.75 21740.51 1.610 18365.51 1.906 10 2485 2515 218.60 99.65 21783.49 1.377 18408.49 1.630 18 2430 2450 216.30 97.95 21186.59 0.944 17811.59 1.123 6 2410 2445 217.00 99.80 21656.60 1.616 18281.60 1.914
15 2465 2500 216.30 99.15 21446.15 1.632 18071.15 1.937 5 2460 2490 217.50 99.65 21673.88 1.384 18298.88 1.639
20 2410 2435 217.50 99.15 21565.13 1.159 18190.13 1.374 14 2370 2400 217.75 99.65 21698.79 1.383 18323.79 1.637
Sam
ple
2
13 2370 2410 217.50 99.90 21728.25 1.841 18353.25 2.179 35 2410 2440 217.30 99.20 21556.16 1.39 18181.16 1.650 69 2420 2455 217.35 99.70 21669.80 1.62 18294.80 1.913 63 2435 2490 216.95 99.25 21532.29 2.55 18157.29 3.029 37 2400 2425 216.40 99.25 21477.70 1.16 18102.70 1.381 68 2430 2470 208.50 101.20 21100.20 1.90 17725.20 2.257 40 2410 2445 217.00 99.25 21537.25 1.63 18162.25 1.927 29 2410 2445 217.25 99.65 21648.96 1.62 18273.96 1.915 41 2415 2450 217.10 99.60 21623.16 1.62 18248.16 1.918 71 2440 2485 218.10 100.05 21820.91 2.06 18445.91 2.440
Sam
ple
3
39 2440 2475 216.95 99.35 21553.98 1.62 18178.98 1.925
66 3.7 Water Absorption (5-hours boiling test)
The same 10 bricks used for initial rate of suction tests were used for water
absorption test. The dry mass dm , were as recorded earlier in the initial rate of
suction test.
A large urn was used to accommodate two sets of samples comprising of 20
bricks (Figure 3.5). The bricks arranged in two tiers with spaces in between bricks
and tiers, were boiled for 5 hours and then allowed to cool naturally in the water for
about 18 hours. A minimum of 16 hours and a maximum of 19 hours of cooling
period were recommended by BS 3921. Each brick was weighed and the saturated
mass sm , recorded. Water absorption W, in percentage was calculated using the
following equation 3.4.
( )% 100 s d
d
m mWm−
= …(3.4)
Where,
dm is the dry mass
sm is the saturated mass
The experimental results for Batch.1 were shown in Table 3.6. Detailed
results for other bricks can be found in the Appendix A4.
Figure 3.5: Apparatus for water absorption test
67
Table 3.6: Water absorption of bricks for Batch 1 Brick identification
Dry mass
dm (gm) Saturated mass
sm (gm) W (Water absorption)%
( )100 s d
d
m mm−
7 2415 2670 10.559 5 2460 2710 10.163 1 2380 2640 10.924 13 2370 2670 12.658 8 2410 2640 9.544 14 2370 2645 11.603 4 2370 2625 10.759 20 2410 2665 10.581 19 2440 2775 13.730
Sam
ple
1
10 2485 2745 10.463 Mean x = 11.098 Std. dev. s =1.248
2 2390 2590 8.37 9 2435 2760 13.35 11 2415 2665 10.35 3 2435 2650 8.83 15 2465 2700 9.53 17 2430 2720 11.93 12 2420 2675 10.54 18 2430 2625 8.02 6 2410 2690 11.62
Sam
ple
2
16 2445 2740 12.07 Mean x =10.461
Std. dev. s =1.772 39 2440 2695 10.45 69 2420 2685 10.95 35 2410 2680 11.20 41 2415 2695 11.59 37 2400 2655 10.63 29 2410 2685 11.41 40 2410 2670 10.79 68 2430 2745 12.96 63 2435 2735 12.32
Sam
ple
3
71 2440 2710 11.07 Mean x =11.337
Std. dev. s =0.248
3.8 Compressive Strength
The bricks were tested for their compressive strength by imposing the bricks
to compression load until failure. The compressive machine used in the laboratory
was the Tonipact, with a capacity of 3000 kN. The machine was calibrated at the
early stage of the duration of the study.
68 In this work a study on the effects of compressive strengths of facing bricks
if tested in different orientations i.e. on its bed, stretcher and header face (Figure 3.7)
were conducted. Common bricks were only tested on their bed face.
Compressive strength tests were carried out on the same bricks after the
absorption test. Thus, the bricks were assumed to be fully saturated resulting from
the 5-hour boiling. To reduce friction caused by irregularities of the surface of the
bricks to be loaded, the bricks, placed in the machine were packed between two
pieces of plywood sheets, cut about 10mm bigger all round than the dimensions of
the brick. A fresh piece of plywood was used for every test.
In the test procedure, British Standard specifies that the rate of loading can
be gradually increased at a convenient rate not exceeding 35 N/mm2 until half of the
anticipated maximum load. Thereafter, the rate could be smoothly reduced to 15
N/mm2 and this rate to be maintained until failure. Although a higher rate of loading
could be used before half of the expected failure load, a constant rate of 15 N/mm2
were applied throughout the test in this work. A higher rate of loading was allowed
merely to reduce the time of testing and it is explained in the BS that higher rate of
loading at this stage has no influence on the ultimate strength. Therefore, a constant
rate of loading of 15 N/mm2 used throughout the test was justifiable. At failure the
brick collapsed and the machine stopped automatically. The maximum load was
recorded and the strength calculated by dividing the maximum load with the area of
the face subjected to loading i.e. bed face (length × width), stretcher face (length ×
height) or the header face (width × height). These areas used in the calculation were
based on the smaller of the two opposite faces.
Some typical results of compressive strengths of common bricks and facing
bricks for Batch. 1 are shown in Table 3.7 and 3.8 respectively. Example of results
for bricks tested on the stretcher face and header face are shown in Table 3.9 and
3.10 respectively. The complete results for compressive strengths are shown in
Appendix A5
69
Figure 3.6: Compressive machine -Tonipact 3000
Figure 3.7 a: Bricks tested on bed face
Figure 3.7 b: Bricks tested on stretcher face
70
Figure 3.7 c: Bricks tested on header face
Table 3.7: Compressive strength of common bricks for Batch 1 tested on bed
face
Length (mm)
Width (mm)
Area 1 (mm2)
Length (mm)
Width (mm)
Area 2 (mm2)
Smaller area
(mm2)
Maximum load Kn.
Compressive Strength N/mm2
216.10 99.25 21447.93 216.20 99.50 21511.90 21447.93 825.30 38.48 215.90 97.45 21039.46 215.50 97.45 21000.48 21000.48 829.30 39.49 217.50 100.05 21760.88 217.45 100.25 21799.36 21760.88 631.30 29.01 218.55 99.15 21669.23 219.05 99.95 21894.05 21669.23 866.30 39.98 217.85 98.95 21556.26 217.70 101.45 22085.67 21556.26 671.30 31.14 217.25 100.80 21898.80 217.25 101.20 21985.70 21898.80 791.30 36.13 217.95 99.65 21718.72 217.70 100.25 21824.43 21718.72 546.30 25.15 219.20 101.25 22194.00 219.25 100.40 22012.70 22012.70 866.30 39.35 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 613.30 27.79
Sam
ple
1
219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 750.30 34.04 Mean x = 34.06
Std. dev. s = 5.47 214.75 100.00 21475.00 215.70 99.75 21516.07 21475.00 850.0 39.58 214.25 100.75 21585.69 213.85 100.00 21385 21385 813.0 38.02 215.50 100.80 21722.40 215.55 100.75 21716.663 21716.66 783.0 36.05 214.55 100.25 21508.63 215.50 99.45 21431.475 21431.48 582.0 27.16 214.9 100.75 21651.17 215.10 100.70 21660.57 21651.18 855.0 39.49 216.55 100.75 21817.41 216.25 100.95 21830.438 21817.41 730.0 33.46 216.00 100.25 21654.00 216.45 101.00 21861.45 21654 543.0 25.08 216.25 100.50 21733.12 216.15 100.15 21647.423 21647.42 786.0 36.31 216.20 100.75 21782.15 216.25 101.45 21938.563 21782.15 745.0 34.20
Sam
ple
2
215.70 100.40 21656.28 215.50 99.90 21528.45 21528.45 695.0 32.29 Mean x = 34.16
Std. dev. s = 4.90
71
Table 3.7 (cont.) 216.20 99.05 21414.61 216.20 99.35 21479.47 21414.61 830.00 38.76 215.90 97.00 20942.30 215.50 97.45 21000.48 20942.30 790.00 37.72 216.50 100.25 21704.13 217.45 100.30 21810.24 21704.13 636.00 29.30 217.75 99.25 21611.69 219.05 99.95 21894.05 21611.69 840.00 38.87 217.85 98.35 21425.55 217.70 101.25 22042.13 21425.55 567.00 26.46 217.35 100.20 21778.47 217.25 101.20 21985.70 21778.47 794.00 36.46 218.20 99.15 21634.53 217.70 100.25 21824.43 21634.53 543.00 25.10 218.75 101.05 22104.69 219.25 100.40 22012.70 22012.70 833.00 37.84 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 614.00 27.83
Sam
ple
3
219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 749.00 33.98 Mean x = 33.23
Std. dev. s = 5.49
Table 3. 8: Compressive strength of facing bricks for Batch. 1 tested on the
bed face
Length (mm)
Width (mm)
Area 1 (mm2)
Length (mm)
Width (mm)
Area 2 (mm2)
Smaller area
(mm2)
Maximum load Kn.
Compressive Strength N/mm2
216.10 98.50 21285.85 216.20 98.50 21295.70 21285.85 894.10 42.00 212.85 100.00 21285.00 217.85 99.90 21763.22 21285.00 988.80 46.46 217.75 99.35 21633.46 217.90 99.65 21713.74 21633.46 944.90 43.68 218.95 99.95 21884.05 218.75 99.65 21798.44 21798.44 1036.90 47.57 219.50 100.55 22070.73 219.40 100.75 22104.55 22070.73 840.90 38.10 217.25 99.40 21594.65 217.10 99.85 21677.44 21594.65 820.90 38.01 219.50 100.25 22004.88 220.10 100.20 22054.02 22004.88 776.90 35.31 217.20 99.80 21676.56 217.45 99.65 21668.89 21668.89 913.90 42.18 215.20 97.60 21003.52 215.55 98.20 21167.01 21003.52 694.90 33.08
Sam
ple
1
216.60 98.70 21378.42 216.30 98.65 21338.00 21338.00 844.90 39.60 Mean x = 40.60
Std. dev. s = 4.66 217.05 100.50 21813.53 218.15 100.75 21978.61 21813.53 1064.30 48.79 219.25 101.00 22144.25 219.50 101.10 22191.45 22144.25 957.30 43.23 217.30 99.50 21621.35 217.35 99.45 21615.46 21615.46 964.30 44.61 219.90 101.45 22308.86 220.50 101.35 22347.68 22308.86 977.00 43.79 217.50 99.85 21717.38 217.05 100.05 21715.85 21715.85 1091.90 50.28 217.55 99.10 21559.21 217.70 99.00 21552.30 21552.30 1106.00 51.32 216.95 99.25 21532.29 217.00 99.15 21515.55 21515.55 1113.00 51.73 217.50 99.55 21652.13 217.10 99.50 21601.45 21601.45 1187.00 54.95 217.00 100.00 21700.00 217.20 99.85 21687.42 21687.42 965.00 44.50
Sam
ple
2
217.00 99.40 21569.80 216.45 99.25 21482.66 21482.66 1159.90 53.99 Mean x = 48.72 Std. dev. s = 4.40
72 Table 3. 9: Compressive strength of facing bricks tested on the stretcher face
Length (mm)
Width (mm)
Area 1 (mm2)
Length (mm)
Width (mm)
Area 2 (mm2)
Smaller area
(mm2)
Maximum load (Kn.)
Compressive Strength N/mm2
218.00 67.50 14715.00 214.90 67.45 14495.01 14495.01 570.00 39.32 217.00 67.30 14604.10 216.50 66.75 14451.38 14451.38 569.00 39.37 217.55 64.50 14031.98 217.30 64.50 14015.85 14015.85 488.00 34.82 217.25 67.75 14718.69 217.00 68.00 14756.00 14718.69 573.00 38.93 217.10 68.35 14838.79 217.15 68.00 14766.20 14766.20 581.00 39.35 217.95 66.90 14580.86 217.50 67.00 14572.50 14572.50 540.00 37.06 216.85 67.30 14594.01 216.85 68.00 14745.80 14594.01 538.00 36.86 218.00 67.10 14627.80 217.65 66.00 14364.90 14364.90 529.00 36.83 216.50 67.90 14700.35 216.50 68.00 14722.00 14700.35 544.00 37.01
Sam
ple
1
217.70 67.75 14749.18 217.00 67.75 14701.75 14701.75 490.00 33.33
Table 3.10: Compressive strength of facing bricks tested on the header face
Length (mm)
Width (mm)
Area 1 (mm2)
Length (mm)
Width (mm)
Area 2 (mm2)
Smaller area (mm2)
Maximum load (Kn.)
Compressive Strength N/mm2
101.10 68.95 6970.85 101.55 68.42 6948.05 6948.05 18.50 2.66 99.65 68.05 6781.18 99.91 68.00 6793.88 6781.18 27.00 3.98
100.85 67.25 6782.16 100.65 67.00 6743.55 6743.55 23.60 3.50 100.10 67.85 6791.79 100.15 67.77 6787.17 6787.17 26.70 3.93 100.00 68.75 6875.00 99.95 68.30 6826.59 6826.59 15.60 2.29 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.70 4.52
100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 24.30 3.61 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 20.80 3.05 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 27.90 4.27
Sam
ple
2
98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 28.40 4.24
3.9 Soluble Salt Content
Fragments of 10 bricks from the compressive strength test were randomly
selected to represent the exterior and interior of the bricks to make up the sample for
tests on soluble salts content. The sample was prepared by the crushing method as
given in BS : 3921 1985. About 25 gm. of ground brick passing sieve size 150 µm.
were then collected as the sample and dried in the oven at 110 °C.
73
The chemical test to determine the soluble salt content was carried out in the
laboratory of the Science Faculty of the Universiti Teknologi Malaysia. The soluble
salt comprises of water-soluble salts of calcium, magnesium, sodium and potassium
and acid-soluble sulphate. The acid-soluble sulphate was extracted in accordance to
the methods found in BS 3921 Appendix B.3.1 and the water-soluble salts,
Appendix B.4.1.
Sulphate was determined by the gravimetric method as described in BS
3921, Appendix B.3.2.2. In this traditional analytical process sulphate was
precipitated, filtered, and finally burned in a crucible. The mass of the acid soluble
sulphate M in gram was determined using equation 3.5 (BS 3921:1985). Results
showing the percentage of sulphates present in the various samples are shown in
Table 3.11.
( )1 00.4115= −M m m …(3.5)
Where,
0m is the mass of the crucible in gm.
1m is the mass of the crucible and burnt precipitate and paper in gm.
Table 3.11: Percentage of sulphate content in the samples from all batches
Sample
Mass of precipitate in gm. ( )1 0m m−
Mass of sample, W
Mass of sulphate ( )1 00.4115M m m= −
Percentage of sulphate in sample
100%MW
×
1 0.0049 2.6889 0.00202 0.07
Batch 1 2 0.0045 2.5288 0.00185 0.07 1 0.0056 2.4917 0.0023 0.09 2 0.0031 2.0387 0.00128 0.06
Batch 2
3 0.0045 2.0255 0.00185 0.09 1 0.0010 2.0315 0.00041 0.02 2 0.0043 2.0224 0.00177 0.09 3 0.0020 2.0224 0.00082 0.04
Batch 3
4 0.0010 2.0465 0.00041 0.02 1 0.0011 2.0819 0.00045 0.02 2 0.0009 2.0371 0.00037 0.02
Batch 4
3 0.0009 2.0072 0.00037 0.02
74
Calcium, magnesium, sodium and potassium were determined by the
instrumental method. The instrument used was the atomic absorption spectroscopy
(AAS) called GBC Avanta PGF 3000 Spectrometer. The AAS, which measures the
presence of metals in liquid samples works on the principal of atomising a sample
and quantitatively determining the concentration of atoms in the gas phase by
measuring the intensity of light absorbed. The schematic presentation of the process
is shown in Figure 3.8.
Flame
Light source
Sample
Atomizer-burnerMonochromator
Photomultiplier
Figure 3.8: A schematic diagram of an atomic absorption
spectrometer (Hammer, 1996)
Before testing the samples in the AAS, calibration curves for the salts of
calcium, magnesium, sodium and potassium were determined. This was carried out
by running standard solution, with known concentrations of the respective salts, on
the AAS and observing the absorbance readings from AAS (Table 3.12, 3.14 and
3.17). The salts concentrations (x) were plotted against the absorbance (y) to produce
calibration curves for each salt and the relationship between absorbance and
concentration were determined as shown by the equations in Figures 3.9, 3.10 and
3.11 for calcium, sodium and potassium and magnesium respectively.
Salts of calcium, sodium, potassium and magnesium were extracted from the
samples as given in Appendix B of BS 3921:1985. The filtrate from the samples was
run in the AAS which gave the readings of absorbance for each salts. Using the
equations from the calibration curves and with readings of the absorbance from
75 AAS, the concentration of the salts in the samples could be determined. Tables 3.13,
3.15, 3.16 and 3.18 show the corresponding percentage of calcium, potassium,
sodium and magnesium in the samples.
Table 3.12: Standard calibration data for calcium Sample label
Concentration mg/l
Mean Absorbance from AAS
Replicates
Blank 0.002 0.002 0.002 0.002
Standard 1 5 0.202 0.203 0.201 0.202
Standard 2 10 0.41 0.409 0.413 0.41
Standard 3 15 0.618 0.615 0.619 0.62
Standard 4 20 0.814 0.811 0.81 0.82
Standard 5 25 1.023 1.023 1.023 1.023
y = 0,0409x - 0,0004R2 = 0,9999
00,20,40,60,8
11,2
0 5 10 15 20 25 30Concentration,mg/l
Abs
orba
nce
Figure 3.9: Calibration curve for detection of calcium
76
Table 3. 13: Percentage of calcium in samples for all batches
Sample Absorbance from AAS,
y
Concentration, x 0.0004
0.0409yx +
=
mg/l
Volume of solution, v
mL
Weight of sample, w
gm.
Percentage of calcium in sample
6 10010
x vw
××
×
1 0.543 13.286 100.0 10.1117 0.013
Bat
ch 1
2 0.580 14.185 100.0 10.3982 0.014
1 0.122 3.013 100.0 10.1036 0.003
2 0.238 5.854 100.0 10.0147 0.006
Bat
ch 2
3 0.647 15.813 100.0 10.0549 0.016
1 0.414 10.147 100.0 10.0096 0.010
2 0.281 6.904 100.0 10.0337 0.007
3 0.450 11.023 100.0 10.0844 0.011 Bat
ch 3
4 0.284 6.977 100.0 10.0238 0.007
1 0.311 7.636 100.0 10.0161 0.008
2 0.390 9.562 100.0 10.0294 0.009
Bat
ch 4
3 0.420 10.293 100.0 10.0366 0.010
Table 3.14: Standard calibration for sodium and potassium
Sodium Potassium Sample
Label Concentration
mg/l Mean
Absorbance from AAS
Concentration mg/l
Mean Absorbance from AAS
Blank 0.004 0.002
Standard 1 1 0.222 2 0.172
Standard 2 2 0.44 4 0.338
Standard 3 3 0.681 6 0.514
Standard 4 4 0.887 8 0.682
Standard 5 5 1.099 10 0.865
77
y = 0,0865x - 0,0048R2 = 0,9998
y = 0,2201x + 0,0055R2 = 0,9993
0
0,2
0,4
0,6
0,8
1
1,2
0 2 4 6 8 10 12
Concentration Mg/lA
bsor
banc
e
Figure 3.10: Calibration curve for detection of sodium and potassium Table 3. 15: Percentage of potassium in samples for all batches
Sample Absorbance from AAS,
y
Concentration, x 0.0048
0.0865yx +
=
mg/l
Volume of solution, v
mL
Weight of sample, w
gm.
Percentage of potassium in sample
6 10010
x vw
××
×
1 0.282 13.286 100.0 10.1117 0.003
Bat
ch 1
2 0.276 14.185 100.0 10.3982 0.003
1 0.549 3.013 100.0 10.1036 0.006
2 0.743 5.854 100.0 10.0147 0.009
Bat
ch 2
3 0.623 15.813 100.0 10.0549 0.007
1 0.297 10.147 100.0 10.0096 0.003
2 0.511 6.904 100.0 10.0337 0.006
3 0.399 11.023 100.0 10.0844 0.005 Bat
ch 3
4 0.290 6.977 100.0 10.0238 0.003
1 0.352 7.636 100.0 10.0161 0.004
2 0.356 9.562 100.0 10.0294 0.004
Bat
ch 4
3 0.367 10.293 100.0 10.0366 0.004
Potassium Sodium
78
Table 3. 16: Percentage of sodium in samples for all batches
Sample Absorbance from AAS,
y
Concentration, x 0.0055
0.2201yx −
=
mg/l
Volume of solution, v
mL
Weight of sample, w
gm.
Percentage of sodium in sample
6 10010
x vw
××
×
1 0.587 2.642 100.0 10.1117 0.003
Bat
ch 1
2 0.427 1.915 100.0 10.3982 0.002
1 0.791 3.569 100.0 10.1036 0.004
2 0.546 2.456 100.0 10.0147 0.002
Bat
ch 2
3 0.564 2.537 100.0 10.0549 0.003
1 0.316 1.411 100.0 10.0096 0.001
2 0.574 2.583 100.0 10.0337 0.003
3 0.355 1.588 100.0 10.0844 0.002 Bat
ch 3
4 0.332 1.483 100.0 10.0238 0.001
1 0.538 2.419 100.0 10.0161 0.002
2 0.498 2.238 100.0 10.0294 0.002
Bat
ch 4
3 0.374 1.674 100.0 10.0366 0.002
Table 3.17: Standard calibration for magnesium Sample label
Concentration mg/l
Mean Absorbance from
AAS
Blank 0.001 Standard 1 1 0.176 Standard 2 2 0.349 Standard 3 3 0.514 Standard 4 4 0.701 Standard 5 5 0.887
y = 0,1774x - 0,0068R2 = 0,9993
0
0,2
0,4
0,6
0,8
1
0 1 2 3 4 5 6
Concentration mg/l
Abs
orba
nce
Figure 3.11: Calibration curve for detection of magnesium
79
Table 3. 18: Percentage of magnesium in samples for all batches
Sample Absorbance from AAS,
y
Concentration, x 0.0068
0.1774yx +
=
mg/l
Volume of solution, v
mL
Weight of sample, w
gm.
Percentage of magnesium in
sample
6 10010
x vw
××
×
1 0.476 2.722 100.0 10.1117 0.003
Bat
ch 1
2 0.29 1.673 100.0 10.3982 0.002 1 0.428 2.451 100.0 10.1036 0.002 2 0.57 3.251 100.0 10.0147 0.003
Bat
ch 2
3 1.069 6.064 100.0 10.0549 0.006 1 0.694 3.950 100.0 10.0096 0.004 2 0.588 3.353 100.0 10.0337 0.003 3 0.747 4.249 100.0 10.0844 0.004 B
atch
3
4 0.573 3.268 100.0 10.0238 0.003 1 0.477 2.727 100.0 10.0161 0.003 2 0.513 2.930 100.0 10.0294 0.003
Bat
ch 4
3 0.832 4.728 100.0 10.0366 0.005
3.10 Efflorescence
Ten bricks were required for the efflorescence test. Each brick was covered
with plastic sheet around the three sides, leaving one side exposed to the atmosphere
(Figure 3.12). A wide mouth bottle filled with distilled water was then inverted on
top of this exposed surface for a duration of 48 hours. The bottle should always
contain water and toped up whenever necessary. After 48 hours, the bottle was
removed and the exposed surface left to dry for 9 days in the laboratory conditions.
A warm place in the laboratory with natural air circulating was selected for this
purpose. This procedure was repeated but for the second time a drying period of 16
days was allowed. After these cycles of wetting and drying the exposed surface of
each specimen was examined for efflorescence. Efflorescence was rated in
accordance to the bricks that showed maximum effects.
80
Figure 3.12: Efflorescence test
CHAPTER 4
STATISTICAL ANALYSIS OF TEST SPECIMENS
4.1 Introduction
This chapter presents the theoretical approaches to statistical calculations and
methods of sample analyses in deriving estimates of population representation.
4.2 General Approach for Analysing Samples
In principle, the processing of sample data involves several steps. The first
step is usually to describe data characteristics by showing its averages and
dispersion. Data could be represented graphically by the histograms and frequency
curve. Besides showing data distribution, the histogram and frequency curve
provides selection on the probability functions to be used as a mathematical model
in deducing the estimate of population mean from samples.
In a typical statistical analysis, before any estimates could be accepted,
results from samples have to be tested and this is referred to as hypothetical testing.
Quality control charts developed from normally distributed data could be regarded
as a form of hypothetical testing (BS 2846:Part 1:1991- Guide to statistical
interpretation of data). In this graphical form, a quick assessment could be made to
detect the homogeneity of data.
82
The analysis of variance (ANOVA) is another form of statistic hypothetical
testing. In an ANOVA, the F-test is carried out to test the null hypothesis (N.H.) of
no significance difference between variances in samples. From the ANOVA the
components of variance could be analysed and the best estimate of population
variance derived.
4.2.1 Description of Data
A group of observations or data is usually described by computing its
descriptive statistics comprising of its averages which include the mean, median and
mode and its dispersion, consisting of the standard deviation, variance and the range.
The sample mean shows the average value of data in a sample, given by
Equation 4.1 (Bland, 1985)
1Sample Mean = ni ix
xn=∑ …(4.1)
For a set of n values 1 2, ,... nx x x
Where,
x= the measurements or observations
n= the numbers of observations.
The median and the mode are also averages that described the sample. The
median in a set of data is the central observation, the values being ranked in order of
size. In other words, half of the data will have a value less than the median, and the
other half of the data will have a value greater than the median.
Mode is a value that occurs with the greatest frequency. A comparison of the
mean and median and mode can reveal information about skewness of the
distribution curve as illustrated in Figure 4.1.
83
The spread of the data or the dispersion can be measured by the standard
deviation, range, variance and the coefficient of variation (c.v.). These
measurements show the variation of each data from their mean. Variance and
standard deviation is computed using equation 4.2 and 4.3 respectively (Bland,
1985). The standard deviation for a sample is a square root of the variance and is
more often used to describe data. The standard deviation has an advantage over the
variance since it has the same unit as the variable tested. The c.v. given in equation
4.4 is a measurement of relative dispersion since it is given on a percentage basis.
Range (equation 4.5), is the difference between the highest and the lowest data. It is
a quick way of analysing data variation. However, its use is limited to small sample
only since it is obtained from two extreme values without giving consideration on
other data in the range.
The range and standard deviation are related so that for any given value of
observations n, an estimate of the standard deviation, estimates can be made from the
mean value of sample range R (equation 4.6).
( )2
2 1Sample variance, 1
n
ix x
sn
=
−
=−
∑ …(4.2)
( )2
1Sample standard deviation, = 1
n
ii
x xs
n=
−
−
∑ …(4.3)
Coefficient of variation, c.v. = 100 %sx× …(4.4)
Range, = max min i iR x x− …(4.5)
estimates R d= × (BS 2846: Part 1, 1991) …(4.6)
Where,
d is a coefficient based on the number of observations n, given in Appendix
B Table B3.
84
Figure 4.1: Mean, median and mode in a distribution
skewed to the right
4.2.2 Histograms and Normal Distribution Curve
Histograms are statistical graphs showing frequency of data where horizontal
axis and vertical axis represent the class interval (i) and the frequency respectively.
In a histogram, if the number of data were increases, the number of classes will
increase and subsequently the class widths decreases. As a result the histogram
approaches a smooth curve, thus called the frequency distribution curve.
Past observations revealed that most physical measurements could be
approximated to a normal distribution curve (Chatfield, 1979, Paradine and Rivettes,
1960); the approximation improves as number of variables increased. In virtue of the
central limit theorem, we can assume that data would eventually approach a normal
distribution for greater number of data. The normal distribution function also known
as normal probability density functions is given by equation 4.7 (Grimm, 1988).
1 2( ) (2 ) exp ( ) / 2f x x x sπ −= − − …(4.7)
Value of observation Mode
Median
Mean
Frequency
85
Where,
( )f x = normal probability density function for a sample. This refers to the
height of an ordinate at a distance x x− from the mean.
s = standard deviation of sample.
Equation 4.7 is transformed to the standard normal distribution function by
putting ( )z x x s= − as shown by equation 4.8 (Grimm, 1988).
( ) ( )1 2 2( ) 2 exp 2 f z zπ −= − …(4.8)
Where,
( )f z is the normal probability density function for a sample in terms of z.
The computed frequency illustrated in the form of a histogram is given by equation
4.9 (Grimm, 1988).
( )y ni f z s= …(4.9)
Where,
n= number of samples
i= number of units in a class interval
s= standard deviation of sample
The integration of equation 4.8 between any values of z produces the normal
probability function, i.e. the area under the curve between the stated values of z. The
area under the probability curve divided into hundred equal parts gives the percentile
values and a 33-percentile value divides the curve into three parts. Grimm (1988),
highlighted that values falling in the upper 33 percentile could be grouped as those
of high values. The lower 33 percentile are regarded as low values whilst normal
values are those lying in the middle third of the distribution.
4.2.3 Log-normal Distribution Curve
If distribution of data is skewed, where the mean, mode and median are not
coincident as in normal distribution then log normal distribution could be used. The
log-normal distribution is essentially the same as the normal, but with ln (x)
86
substituted for x. The log-normal has probability distribution function given by
equation 4.10. Grimm (1988) suggested that log-normal distribution is useful for
data with c.v. (ν ) exceeding 30%.
( )20.5 1 2( ) (2 ) ( ) exp ln / 2f x x xπ β α β− − = − − …(4.10)
( ) 0.52ln 1xα ν− = +
…(4.11)
s xν = …(4.12)
( ) 0.52ln 1β ν = + …(4.13)
Where,
( ) 1lnz x α β −= − …(4.14)
( )0.5 1 2( ) (2 ) exp 2f z z zπ β β α− − = − − − …(4.15)
( )y ni f z= …(4.16)
Where,
y = the histogram ordinate at any value of x in the histogram,
n = number of data in the histogram,
i = x interval in the histogram,
ν = c.v. in decimal.
An application of this statistical analysis will be demonstrated in section 4.3
for samples used in this research.
4.2.4 Derivation of Population Estimates
Assuming that data is normally distributed, therefore the functions of the
normal distribution curve could be used to derive estimates for the population.
For a normal distribution curve the integration of equation 4.8 of the normal
curve between specified limits is a probability function, which represents the area
87
under the normal curve. The full range of this probability function could be found in
statistical table. However, limits, which are of importance to this work is shown here
in Figure 4.2. From Figure 4.2 it can be seen that approximately 70 % of sample
data will lie within the area covered by a point on each side of the mean value,
denoted by one unit of standard deviation i.e.1σ . About 95 % will lie within the
area bounded by 1.96σ on each side of the mean and 99 % at 3.09σ from each side
of the mean. The distribution at 95 % probability is important in a production. It
provides a 95 % confidence that not more than 1 in 40 results would be below the
required specification limits. Therefore, a 95 % confidence of the population mean
can be estimated from sampling distribution using equation 4.17 (Bland, 1985).
1.96x s nµ = ± …(4.17)
Where,
µ = population mean
x = sample mean
s = sample standard deviation
n = sample size
Figure 4.2: Areas under normal probability curve
In virtue of the central limit theorem, the estimate is good on normally
distributed data with large samples size, i.e. n greater than 30 (Bland, 1985 and
Triola, 1989). If n is smaller than 30 the distribution of sample data will follow, the t
3413
%
3413
%
13.6
0%
13.6
0% 2.14% 2.14%
f(x), f(z)
x = -1σ x= -1.96σ x=1σ x=1.96σ x x= -3.09σ x= 3.09σ x= 0 z=-3.09 z=-1.96 z=-1 z=0 z=1 z=1.96 z=3.09 z
88
distribution and value of 1.96 from equation 4.7 will be replaced by ct (the
percentage point of the t distribution which can be obtained from Appendix B Table
B2). Thus, the population estimate of the mean (µ ) for a small sample is given by
equation 4.18 (Bland, 1985).
csx tn
µ = ± …(4.18)
The t-distribution, formulated by W.S. Gosset in 1908 has similar properties
to the normal distribution except that it has more spread about the mean as shown in
Figure 4.3. Another important feature of the t-distribution is that it has different
curves for different sample sizes. The t distribution depends on a parameter called
degrees of freedom (df) given by n-1, where n denotes the samples size.
(Mean)x
N orm al distribution
distribution w ith n=10t −
distribution w ith n=20t −
Figure 4.3: T-distribution curves for various values of n
(Chatfield, 1978)
The sample size in this research is smaller than 30, therefore, the t-
distribution was used in conjunction with equation 4.18 to arrive at the mean value
of the population. Example of these will be illustrated in section 4.3.4.
89
4.2.5 Hypothesis Testing
4.2.5.1 Analysis of Variance (ANOVA)
The analysis of variance (ANOVA) is a statistical tool developed from
normal distribution theory and is used for testing the significance difference of
several means. The ANOVA in testing a hypothesis that there is no difference in the
means between samples is called a single factor ANOVA.
A single factor ANOVA is accomplished by analysing the variance and by
partitioning the total variance into two, the component due to true random error i.e.
within samples ( withinMS ) and the component due to differences between means of
several samples ( betweenMS ). These two components are compared by means of an F-
test as shown in equation 4.19.
calc between withinF MS MS= …(4.19)
If calcF is smaller than the value of the critF given in statistical table of the F-
distribution (Appendix B Table B1), then the N.H. is accepted. This implies that
there is no significant difference between the means of the several samples and
within samples and therefore, the best estimate for the variance is the total variance
from within and between samples. On the other hand if calcF is larger than critF , then
the differences between the variance is considered significant. Therefore, the null
hypothesis of no differences between means is rejected and the alternative
hypothesis that the means are significantly different is accepted. Table 4.1 shows the
components of variance for the case when the N.H. is accepted or rejected.
90
Table 4.1: Components of variance from ANOVA Source of Variation
Sum of Squares
SS
Degrees of Freedom
df
Mean square MS
(2)÷(3)
When the N.H. is accepted the mean square is an estimate of
When the N.H. is rejected the mean square (MS) is an
estimate of (1) (2) (3) (4) (5) (6)
Between samples
betweenSS . 1No of samples − betweenSS df÷ 2σ 2 2
rcσ σ+ c= sample size
Within samples
withinSS
. Total specimensin samples No of
samples− withinSS df÷ 2σ 2σ
Total between
within
SSSS+
1
Total specimensin samples −
Total SSTotal df
÷ Best estimate of
2σ -
Referring to Table 4.1 of the ANOVA, when the N.H. is rejected, the mean
square (MS) is an estimate of 2 2rcσ σ+ . With c known i.e. size of sample and the
value of 2 2rcσ σ+ can be obtained from col. (4) of Table 4.1, 2
rσ the variance
between samples can be computed. This gives the new estimate of population
variance from the ANOVA as 2 2rσ σ+ (Loveday). In this study, the ANOVA was
particularly used to derive the best estimate for the variance between and within
samples in estimating the population means.
4.2.5.2 Control Charts
Control charts are graphical techniques used mainly to assess quality of a
production in an industry since it gives a rapid indication of the population quality
and enables appropriate action to be undertaken when necessary. A process is said to
be in control if there is no significant changes in the means and standard deviation.
Thus two control charts are required, one for monitoring the mean and the other one
for monitoring the variations. Examples of control charts for means and ranges are
as shown in Figures 4.4 and 4.5 respectively.
The three basic components of a control charts (Figure 4.4) are:
(i) A centre line, which represents the mean, for the respective mean or
range chart of samples.
91
(ii) Statistical control limits, i.e. the upper and lower action and warning
lines. These define the constraints for variations and if exceeded
shows that the process is out of control or data is not homogeneous.
(iii) Performance data plotted over time of production.
Two pairs of control limits are used. The first pair represents warning or
inner limits. These are set so that there is a 2.5 % probability (1 in 40) of a sample
mean having a value below the lower limit and a 2.5 % probability of its having a
value above the upper limit. The action or outer limits are set so that there is a
probability of 0.1 % (1 in 1000) of the mean falling above the upper limit and a
probability of 0.1 % of its falling below the lower limit. A process is said to be in
statistical control if only 1 out of 40 samples is found outside the warning lines and
1 out of 1000 samples outside the action lines.
Control charts could also be used to test homogeneity of data in samples (BS
2846: Part 1:1991- Guide to statistical interpretation of data). In terms of
homogeneity the occurrence of a single point outside 1 in 1000 control lines or of
more than one or two outside the 1 in 40 control lines is considered to be evidence
that data are not homogeneous.
The upper and lower warning and action lines for means are given by
equation 4.20 and 4.21.
Warning lines = 1.96 xx σ± …(4.20)
Action lines = 3.09 xx σ± …(4.21)
Where,
x = mean of sample means
xσ = standard deviation of mean
xsn
σ = …(4.22)
Where s is the estimate of the population standard deviation and n the sample size.
The value s is given in equation 4.6.
s Rd= …(4.23)
92
Hence, the warning limits for the mean (MWL)= 1.96Rdxn
± …(4.24)
Putting '0.025
1.96d An
= , the warning limit for the mean become
MWL = '0.025x A R± …(4.25)
Similarly the action limits for the mean (MAL) are
MAL = 3.09Rdxn
± …(4.26)
Putting '0.001
3.09d An
= , the action limits for the mean become
MAL = '0.001x A R± …(4.27)
In the range chart, warning (RWL) and action (RAL) lines are given by
equation 4.28, 4.29, 4.30 and 4.31 respectively (BS 2846: Part 1:1991).
The upper RWL = '0.025D R …(4.28)
The lower RWL = '0.975D R …(4.29)
The upper RAL = '0.001D R …(4.30)
The lower RAL = '0.999D R …(4.31)
The control limit factors ' ' for mean and for rangeA D can be obtained from
Appendix B, Table B4.
93
1 5
Sam
ple
mea
n
1 5
Sam
ple
rang
e
Figure 4.4: Control charts for sample means and ranges
(Neville, 1985)
4.3 Application of Statistical Methods for Samples Under Investigation
The statistical principles explained in section 4.2 were used throughout the
work for processing sample data. The statistical computations in this work were
facilitated by the computer software, Microsoft Excel 2000.
Mean
Upper warning line
Upper action line
Lower warning line
Lower action line
10 15 20 25 Sample Number
115
120
125
130
110
Mean
Upper warning line
Upper action line
Lower warning line Lower action line
10 15 20 25 Sample Number
5
10
15
20
0
94
An example of the application of these analyses is shown here with the
results of water absorption test. The statistical process as shown in Figure 4.5 is
described below:
i) First, the average and dispersion of data from samples in all batches
were determined through the computations of the descriptive
statistics consisting of the mean, median, mode, standard deviation,
range, and c.v. (Table 4.2).
ii) The distribution of data was shown graphically by plotting the
histogram. Assuming data to be normally distributed a normal curve
fit was computed (Table 4.4) and the normal curve superimposed on
the histogram as shown in Figure 4.6. Using the normal probability
function the 33-percentile values were determined to identify the
distribution of data for good, medium and low values corresponding
to the upper, middle and lower 33-percentile values.
iii) Control charts of samples means and ranges were plotted to check the
homogeneity of data. The data were examined for outliers i.e. data
not complying with control charts criteria for homogeneity and would
be regarded as not representing the population in the study and thus
ignored in the analysis of estimates.
iv) The F-test from ANOVA was performed to test the null hypothesis
that there was no significant difference between the variances in the
samples. From the ANOVA the components of variance were used to
derive estimate of population variance.
v) Lastly, estimates of population mean for small sample i.e. n< 30 at 95
% confidence were deduced using equation 4.18. Since the size of
samples i.e. number of specimens in a sample were less than 30 for
all the tests considered in this research therefore, equation 4.18 were
used throughout in this study.
95
Figure 4.5: Process of statistical analysis
Descriptive statistics
Mean Median Mode Standard deviation Range Coefficient. of variation
Histogram and frequency curve
ANOVA /F-test
Control charts
To test data homogeneity
To test significance of difference in the variance of samples
Deducing population estimates
Homogeneous
No significance difference in the variance
Non-homogeneous
Examine data for outliers
Components of variance
Significant
Data
Deriving estimates from normal probability function
Assuming data to be normally distributed
96
4.3.1 Description and Presentation of Sample Data
Water absorption in every specimen of bricks from samples in Batches 1, 2,
3 and 4 were determined and the descriptive statistics consisting of the mean,
median, mode, standard deviation, variance, range, and c.v. for all data were
computed and tabulated (Table 4.2).
The graphical presentation of data is shown by plotting the histogram and the
normal curve fit. To plot the histogram, data were grouped into 10 classes. In
accordance to BS 2849 (Guide to statistical interpretation of data), groupings could
consist of between 10 and 20 classes. Having decided on the number of classes, the
class intervals (i) were determined. From Table 4.2, the maximum value was 14.376
and the minimum was 7.655. The range (R) is the difference between the maximum
and the minimum. If there were 10 class intervals, there were about R/10 or 0.7 units
per class interval, i.e. i = 0.7. The frequency of data occurrence against these
selected class intervals could then be determined. Data frequency distribution is
given in Table 4.3 and its histogram plotted as shown in Figure 4.6. It could be
observed from the histogram that a few range of high values were located
approximately towards the centre of the distribution and smaller values tailing on
both sides from the centre, a typical feature of a normally distributed data.
Therefore, in virtue of the central limit theorem, with greater number of data it could
be assumed that the contour of the histogram would eventually approach a normal
curve.
Since data were assumed to be normally distributed a curve normalised to fit
in the distribution were constructed. In the construction of the normal curve, the
ordinates were computed at every midpoint of the intervals in the histogram using
equation 4.9. These ordinates as shown in column 5 of Table 4.4 were used to plot
the normal curve, which is superimposed on the histogram (Figure 4.6). From the
normal curve, it was seen that the values of the mean, median and mode did not
coincide meaning that it was skewed. In cases like this, Grimm (1988) suggested
that normal curve function could still be used for the probability analysis if the c.v.
of data in the samples does not exceed 30%.
97
Coefficient of variation was found to be 11.4 % which is less than 30 % and
therefore, in accordance to Grimm do not require a log-normal function for its
probability analysis. However, a log-normal curve was plotted to verify this theory
by Grimm. The ordinates for the log-normal curve were derived using equations
4.11 through equations 4.16.These ordinates as shown in column 8 of Table 4.4 were
used to plot the log-normal curve (Figure 4.6). It was found that it almost overlap
with the normal curve. Hence, this proved Grimm’s theory that a log-normal curve is
only useful for data with c.v. of more than 30%.
To enhance the application of this theory further, some verifications
regarding this application for a case of higher c.v. was felt necessary. Therefore,
results for compressive strength of common bricks having a c.v. of 25.4 %, was
computed for its log-normal curve. Table 4.5 shows the computed normal and log-
normal frequency at the midpoint of each interval in the histogram and with these
data, the normal and log-normal curves were drawn on the histogram (Figure 4.7). It
was found that there was a greater shift between these two curves. In order to check
the reliability of results, if probability is based on normal curve for such cases, the
33 percentile values for both the normal and log-normal curve were computed. The
33 percentile values for the normal curve were computed with the aid of the
Microsoft Excel statistical programme. As for the log-normal curve, since,
1(ln )z x α β −= −
Therefore, exp( )x zβ α= + …(4.32)
The upper 33 percentile was at z = 0.4317 and lower 33 percentile was at
z = -0.4317 (From Table 4.7). Using equation 4.11 and 4.13 to calculate values of
α and β , x could then be determined from equation 4.32 for both the upper and
lower 33 percentile values. These values were compared against the values from the
normal curve and tabulated in Table 4.6. It was found that the differences were
relatively small, approximately 2.5%. Therefore, this verified Grimm’s theory that
the normal distribution probability function could be used for data with c.v. less than
30 %.
98
Table 4.2: Water absorption of specimens in each sample for facing bricks
Sample
Water Absorption in specimens (%)
1 10.56 10.16 10.92 12.66 9.54 11.60 10.76 10.58 13.73 10.46 2 8.37 13.35 10.35 8.83 9.53 11.93 10.54 8.02 11.62 12.07
Batch
1 3 10.45 10.95 11.20 11.59 10.63 11.41 10.79 12.96 12.32 11.07 4 11.58 12.59 10.71 10.80 11.57 12.03 10.83 11.25 13.37 10.58 5 11.83 12.93 12.22 13.79 11.13 10.40 12.40 11.18 12.44 10.91 6 10.82 13.12 12.37 12.43 10.87 11.49 10.04 11.93 11.26 11.20 7 12.03 11.45 10.85 11.60 11.74 12.33 12.21 12.98 12.95 11.93 8 12.36 10.36 10.12 12.37 11.56 10.65 11.99 11.53 12.25 10.45 9 11.89 12.70 11.20 9.65 11.56 11.94 11.12 12.75 13.15 12.02 10 12.01 10.37 11.63 10.03 11.70 12.79 10.29 9.40 12.15 13.55
Batch 2
11 13.14 11.45 12.67 12.10 11.03 12.25 12.15 11.14 11.76 11.52 12 11.89 11.30 12.05 12.70 10.49 10.52 10.38 12.74 10.43 11.29 13 9.86 8.95 11.01 11.40 11.77 10.21 11.55 11.95 12.25 10.78 14 12.37 11.16 12.21 10.55 12.12 12.83 11.12 10.66 11.31 11.01 15 11.87 11.63 10.50 10.30 11.08 11.79 9.15 10.84 11.71 10.00 16 7.66 10.31 11.33 12.03 9.67 11.36 11.55 10.30 10.84 9.84 17 8.84 9.18 9.27 8.80 10.13 9.59 9.25 9.12 9.49 10.37 18 10.37 10.24 11.05 10.29 11.51 11.91 11.41 11.41 9.46 10.57
Batch 3
19 11.15 10.82 12.09 9.35 9.86 10.11 10.24 10.45 12.17 11.41 20 8.57 13.61 11.63 12.40 11.04 11.47 8.47 11.64 9.97 11.69 21 12.61 8.64 12.14 11.74 9.67 12.09 12.03 8.61 11.78 8.25 22 10.32 9.64 11.44 11.08 10.62 13.99 13.33 11.10 9.86 10.03 23 9.31 13.14 11.98 10.36 12.74 12.94 9.31 12.74 13.52 11.34 24 12.29 10.95 13.03 12.61 13.48 12.44 12.75 14.38 12.11 11.91 25 12.71 8.94 9.56 11.69 12.36 13.39 10.69 11.76 12.67 11.13 26 11.70 7.93 9.34 10.06 11.65 12.09 8.58 9.23 11.05 13.02
Batch 4
27 12.54 12.17 12.00 7.92 12.67 12.40 11.33 8.83 11.46 11.76 Descriptive Statistics Mean, x = 11.23% Median = 11.35 % Mode = 12.25 % Variance = 1.649 Standard deviation, s = 1.284 % Maximum = 14.377 Minimum = 7.655 Range, R = 6.72 % Coefficient of variation, c.v. = 11.43 %
99
Table 4.3: Frequency distribution of data for facing bricks
Class interval Frequency 7.555-8.255 6 8.255-8.955 15 8.955-9.655 19
9.655-10.355 24 10.355-11.055 48 11.055-11.755 59 11.755-12.455 58 12.455-13.155 28 13.155-13.855 10 13.855-14.555 3
010203040506070
7.55
5-8.
255
8.25
5-8.
955
8.95
5-9.
655
9.65
5-10
.355
10.3
55-1
1.05
5
11.0
55-1
1.75
5
11.7
55-1
2.45
5
12.4
55-1
3.15
5
13.1
55-1
3.85
5
13.8
55-1
4.55
5
Water absorption in percentage
Freq
uenc
y
Figure 4.6: Histogram, normal curve and log-normal curve, for water
absorption of bricks
Normal curve
Log- normal curve
11.23%11.3%
12.25%1.28
. . 11.4%
==
===
xMedianModesc v
Low<10.68 % Normal=10.68- 11.85 % High >11.85 %
100
Table 4.4: Normal and log-normal curve fit for water absorption
Normal curve Log-normal curve
Interval midpoint
Observed frequency
Number of standard deviations, z (x - x) s
( )f z
( ) ( )-1 2 22π exp - z 2
Computed frequency ordinate, y
( )ni f z s (Normal curve in Fig. 4.6 shown in red.)
Number of standard deviations, z ( ) -1ln x - α β
( )f z
( )( )
-0.5 -1
2
2π β
exp - z 2 - βz - α
Computed frequency ordinate, y
ni f(z) (Log-normal curve in Fig. 4.6 shown as broken line.)
(1) (2) (3) (4) (5) (6) (7) (8)
7.905 6 -2.589 0.014 2.059 -3.023 0.005 0.866 8.605 15 -2.043 0.049 7.278 -2.279 0.030 5.728 9.305 19 -1.498 0.130 19.112 -1.593 0.106 19.995 10.005 24 -0.953 0.253 37.282 -0.956 0.221 41.849 10.705 48 -0.408 0.367 54.029 -0.363 0.306 57.851 11.405 59 0.137 0.395 58.167 0.193 0.301 56.933 12.105 58 0.682 0.316 46.520 0.715 0.224 42.312 12.805 28 1.228 0.188 27.639 1.208 0.132 24.889 13.505 10 1.773 0.083 12.199 1.675 0.064 12.035 14.205 3 2.318 0.027 4.000 2.119 0.026 4.934
101
Table 4.5: Normal and log-normal curve fit for compressive strengths of common bricks
Normal curve Log-normal curve
Interval midpoint
Observed frequency
Number of standard deviations, z (x - x) s
( )f z =
( ) ( )-0.5 22π exp - z 2
Computed frequency ordinate, y
( )ni f z s
Number of standard
deviations, z ( ) -1ln x - α β
( )f z =
( )( )
-0.5 -1
2
2π β
exp - z 2 - βz - α
Computed frequency ordinate, y
( )y ni f z=
(1) (2) (3) (4) (5) (6) (7) (8)
20.35 14 -1.695 0.095 5.025 -2.126 0.0082 3.9287 24.35 11 -1.253 0.182 9.630 -1.408 0.0243 11.6834 28.35 11 -0.812 0.287 15.191 -0.799 0.0409 19.6463 32.35 14 -0.371 0.372 19.721 -0.271 0.0476 22.8401 36.35 18 0.070 0.398 21.071 0.196 0.0431 20.6849 40.35 24 0.512 0.349 18.530 0.614 0.0328 15.73416 44.35 10 0.953 0.253 13.412 0.992 0.0220 10.5646 48.35 13 1.394 0.151 7.990 1.338 0.0135 6.4784 52.35 4 1.836 0.074 3.918 1.656 0.0077 3.7163 56.35 1 2.277 0.029 1.581 1.951 0.00423 2.0291
102
0
5
10
15
20
25
30
18.3
5-22
.35
22.3
5-26
.35
26.3
5-30
.35
30.3
5-34
.35
34.3
5-38
.35
38.3
5-42
.35
42.3
5-46
.35
46.3
5-50
.35
50.3
5-54
.35
54.3
5-58
.35
Compressive Strength N/mm2
Freq
uenc
y
Figure 4.7: Histogram, normal curve and log-normal curve for compressive
strength of common bricks (c.v. approaching 30%)
Table 4.6: Comparisons of 33 percentile values from normal and log-normal
curve for compressive strength of common brick Percentile Normal curve Log-normal curve
33 31.86735 31.07525
67 39.53042 38.55586
Table 4.7: Probability that x will not be exceeded (adapted
From Grimm, 1988) Probability, % z 1 -2.3267 5 -1.645 10 -1.28 20 -0.842 25 -0.674 30 -0.524 33.3 -0.4317 40 -0.253 Mode β− 50 (median) 0 Mean 2β 60 0.253 66.7 0.4317 70 0.524 80 0.842 90 1.28 95 1.645 99 2.3267 99.5 2.575 99.9 3.10
Log-normal curve
Normal curve
103
4.3.2 Test for Data Homogeneity
The control chart was used for testing data homogeneity. The first step in the
construction of the control chart was to divide the observations into a convenient
subgroup on a time basis. The 27 samples constitute the subgroups. The means and
ranges of each sample were then determined (Table 4.8).
The means and ranges for every sample were plotted for the respective mean
and range chart (Figure 4.8 and 4.9).The upper and lower warning limits (MWL)
and action limits (MAL) for the mean chart were determined using equations 4.25
and 4.27, respectively. With respect to the range chart, the upper and lower warning
limit (RWL), were computed from equations 4.28 and 4.29 respectively. While, the
upper and lower action limits (RAL) were determined from equation 4.30 and 4.31,
respectively. These values for control limits were shown in Table 4.9.
From the control chart for sample means in Figure 4.8 it could be seen that
there were 2 points each located outside the upper and the lower action lines. These
two points from sample 17 and 24 were considered as outliers and were assumed to
contribute to the non-homogeneity of data. Therefore, to be reasonably confident
that estimates derived from samples were representative of the population these two
data points were disregarded in the analysis of the population mean. On the other
hand, the range chart in Figure 4.9 was found to be in compliance with the
requirements of homogeneity criteria of a control chart since all the data points are
within the inner control limits (RWL). This may indicate that the production had
achieved a reasonably good control over the variance.
104
Table 4.8: Sample means and ranges for water absorption
Sample no. Mean Range
1 11.098 4.186
2 10.461 5.322
3 11.337 2.512
4 11.531 2.796
5 11.923 3.396
6 11.552 3.074
7 12.007 2.131
8 11.367 2.246
9 11.797 3.496
10 11.393 4.145
11 11.921 2.117
12 11.379 2.362
13 10.973 3.297
14 11.534 2.279
15 10.887 2.718
16 10.489 4.374
17 9.404 1.572
18 10.822 2.452
19 10.765 2.816
20 11.048 5.137
21 10.756 4.358
22 11.141 4.355
23 11.738 4.210
24 12.592 3.430
25 11.489 4.454
26 10.464 5.088
27 11.309 4.751
Grand Mean, x 11.229
Mean Range, R 3.788
Table 4.9: Control limits for means and ranges for water absorption
Grand mean, x = 11.229 Mean range, R = 3.788
For means For ranges Warning lines Action lines Lower
action line Lower warning line
Upper warning line
Upper action line
0.202x R± =11.994, 10.464
0.317x R± =12.430, 10.028
0.35R× = 1.326
0.54R× =2.046
1.55R× =5.872
1.94R× =7.349
105
9,009,50
10,0010,5011,0011,5012,0012,5013,00
0 5 10 15 20 25 30
Sample NumbersW
ater
Abs
rptio
n (%
)M
ean
Figure 4.8: Control chart for mean values of water absorption
0.001.002.003.004.005.006.007.008.00
0 5 10 15 20 25 30
Sample Numbers
Wat
er A
bsor
ptio
n (%
)R
ange
Figure 4.9: Control chart for ranges of water absorption
4.3.3 Determination of Sample Variance Using the ANOVA
A single factor ANOVA at 95 % confidence was carried out on the
remaining 25 samples (Table 4.10), after ignoring the two samples i.e. sample no
17 and 24, which were found to contribute to the non-homogeneity of data. Table
4.11 shows the results from ANOVA a single factor analysis carried out using a
statistical programme by Microsoft Excel 2000. From ANOVA it was found
that calcF was smaller than critF which indicates that the differences between the
means in the samples from the different batches were not significant and therefore
Upper action line Upper warning line
Mean
Lower warning line Lower action line
Lower action line Lower warning line
Upper warning line Upper action line
Mean
106
the N.H. is accepted. From here the best estimate for the variance derived was 1.53
as shown in column 4 of Table 4.11
Table 4.10: Samples accounted for in the estimate of population
mean for water absorption
Sample
Water Absorption in specimens (%)
1 10.56 10.16 10.92 12.66 9.54 11.60 10.76 10.58 13.73 10.46 2 8.37 13.35 10.35 8.83 9.53 11.93 10.54 8.02 11.62 12.07
Batch
1 3 10.45 10.95 11.20 11.59 10.63 11.41 10.79 12.96 12.32 11.07 4 11.58 12.59 10.71 10.80 11.57 12.03 10.83 11.25 13.37 10.58 5 11.83 12.93 12.22 13.79 11.13 10.40 12.40 11.18 12.44 10.91 6 10.82 13.12 12.37 12.43 10.87 11.49 10.04 11.93 11.26 11.20 7 12.03 11.45 10.85 11.60 11.74 12.33 12.21 12.98 12.95 11.93 8 12.36 10.36 10.12 12.37 11.56 10.65 11.99 11.53 12.25 10.45 9 11.89 12.70 11.20 9.65 11.56 11.94 11.12 12.75 13.15 12.02 10 12.01 10.37 11.63 10.03 11.70 12.79 10.29 9.40 12.15 13.55
Batch 2
11 13.14 11.45 12.67 12.10 11.03 12.25 12.15 11.14 11.76 11.52 12 11.89 11.30 12.05 12.70 10.49 10.52 10.38 12.74 10.43 11.29 13 9.86 8.95 11.01 11.40 11.77 10.21 11.55 11.95 12.25 10.78 14 12.37 11.16 12.21 10.55 12.12 12.83 11.12 10.66 11.31 11.01 15 11.87 11.63 10.50 10.30 11.08 11.79 9.15 10.84 11.71 10.00 16 7.66 10.31 11.33 12.03 9.67 11.36 11.55 10.30 10.84 9.84 18 10.37 10.24 11.05 10.29 11.51 11.91 11.41 11.41 9.46 10.57
Batch 3
19 11.15 10.82 12.09 9.35 9.86 10.11 10.24 10.45 12.17 11.41 20 8.57 13.61 11.63 12.40 11.04 11.47 8.47 11.64 9.97 11.69 21 12.61 8.64 12.14 11.74 9.67 12.09 12.03 8.61 11.78 8.25 22 10.32 9.64 11.44 11.08 10.62 13.99 13.33 11.10 9.86 10.03 23 9.31 13.14 11.98 10.36 12.74 12.94 9.31 12.74 13.52 11.34 25 12.71 8.94 9.56 11.69 12.36 13.39 10.69 11.76 12.67 11.13 26 11.70 7.93 9.34 10.06 11.65 12.09 8.58 9.23 11.05 13.02
Batch 4
27 12.54 12.17 12.00 7.92 12.67 12.40 11.33 8.83 11.46 11.76 Mean = 11.247
Table 4.11: ANOVA and components of variance for water absorption Source of Variation
Sum of square
(SS)
Degrees of
freedom (df)
Mean square (MS)
When the N.H. is accepted the mean square is an estimate of
When the N.H. is rejected the mean square is an estimate of
calc.F
between
within
MSMS
÷
crit.F From
F-Table
(1) (2) (3) (4) (5) (6) (7) (8)
Between rows 51.487 24 2.1453 2σ 2 2rcσ σ+
Within rows 329.94 225 1.4664 2σ 2σ
Total 381.43 249 1.53 Best estimate of
2σ
1.463 1.566
107
4.3.4 Estimates of Population Mean
The estimates for the population meanµ , were determined using equation
4.18. This estimate was based on the remaining 25 samples (Table 4.10) after
ignoring data from sample 17 and 24, which were considered as not representative
of the population.
csx tn
µ = ±
Where,
x = mean for sample = 11.247 (Table 4.10)
tc = 2.262 (From Appendix B, Table B2)
s =sample standard deviation = 1.53 ( 2 1.53s = derived from ANOVA)
n = sample size = 10
1.5311.247 2.262 10.36 12.1310
toµ∴ = ± =
The mean for water absorption in percentage was11.247 0.885± i.e. ranging
from 10.36 % to 12.13 %. Therefore, water absorption for the population falls in the
range of 10 % - 12 %.
4.4 Conclusions
In norm with the central limit theorem it is widely acknowledged that most
physical measurements could be assumed normally distributed. On this basis
therefore, the normal probability function has been used throughout this work for
processing sample data. The validity of the normally distributed assumption is
verified as shown by the results of the histogram plot for the various tests. A typical
example taken for the water absorption tests showed that most data were
concentrated about the mean and it could be assumed that the histogram would
approach a normal curve as the size of data increases. Similarly, the other results
108
comprising of the dimensional tolerance, IRS, density and compressive strength also
displayed comparable characteristics of a normally distributed data.
The population mean derived from normal probability curve is good if size
of sample is large i.e. a sample having more than 30 data. In this work, however,
there were less than 30 bricks in a sample. Hence, the sample was considered small.
Under this condition the percentage points from the t-distribution curve was used to
derive the population estimates.
Control charts are graphical techniques used mainly to assess quality of a
production. It consists of performance data plotted against the control limits, i.e. the
upper and lower action and warning lines. These control limits define the constraints
for variations and if exceeded shows that the process is out of control or data is not
homogeneous. For this research samples, which did not satisfy the homogeneity
criteria, set by these control limits were considered as not representative of the
population and were not accounted for in the derivation of population estimates.
In a normal curve, data are symmetrically distributed about the mean, i.e. the
mean, median and mode are all coincident on the curve. The histogram plotted for
data in this work reveals some skewness in the data distribution for which the mean,
median and mode were not coincident. For this case, the coefficient of variation
(c.v.) is used to indicate the reliability of the assumption of a normal curve. Grimm
suggested that the log-normal probability function would be found helpful for data
having c.v.’s exceeding 30 %. In the log-normal distribution the natural logarithm is
normally distributed. With respect to this, the c.v.’s determined for dimensional
tolerance, density, IRS, water absorption and compressive strengths, for facing
bricks loaded on its bed and stretcher face and common bricks were all below 30 %
and therefore did not need the log-normal probability function. However, to further
justify the appropriateness of the normal probability function application in the
analyses, the 33-percentile values for the compressive strength of common bricks
with a c.v. of 25.4 % were computed for both the normal and log-normal curves.
Results showed comparatively small differences between the two values verifying
that the normal probability function could be used for data with c.v. less than 30 %.
109
In this research samples were taken from the factory in different batches at
intervals of approximately two months. Therefore to ascertain that the differences of
the means in the different batches were not significant a single factor ANOVA was
computed. From the ANOVA the components of variance between the several
samples in the different batches were determined. The variance was then used in
arriving at the population mean.
CHAPTER 5
RESULTS AND DISCUSSIONS
5.1 Introduction
This chapter presents results for the compressive strength, dimensional
tolerance, water absorption, initial rate of suction, density, efflorescence effects and
soluble salt content of bricks. The results were analysed and interpreted through the
process as described in Chapter IV. Comparisons and correlations of the results with
specified limits of other standards were also carried out for the purpose of
evaluation.
Results from efflorescence test and soluble salt content were deduced from
observations based on small samples and hence found not required to be analysed by
the statistical approach as described in Chapter IV.
5.2 Compressive Strength
The compressive strength of facing brick was determined with respect to the
different orientations of testing i.e. on its bed face, stretcher face and header face.
The common bricks were only tested on their bed face. The loaded area used in the
calculation of compressive strength in all cases was the gross area. However,
111
compressive strength for results tests conducted on the bed face was also compared
with results based on calculations using net loaded area. The net loaded area is the
gross area less the area of perforations.
Table 5.1, 5.2 and 5.3 show the compressive strengths of specimens in the
samples for all batches of facing bricks when tested on their bed, stretcher and
header face respectively.
Table 5.1: Compressive strength of specimens in each sample for facing
bricks tested on bed face Sample Compressive strength N/mm2
1 42.0 46.5 43.7 47.6 38.1 38.0 35.3 42.2 33.1 39.6
Batch 1 2 48.8 43.2 44.6 43.8 50.3 51.3 51.7 55.0 44.5 54.0
3 35.6 41.8 44.7 35.8 31.0 45.5 40.6 35.5 42.9 36.2 4 36.5 41.1 48.4 38.5 30.6 29.4 27.1 38.3 35.6 29.7 5 56.3 41.0 57.7 41.8 34.1 46.5 52.0 59.0 40.0 42.1
Batch 2
6 39.9 39.0 45.8 48.6 40.4 43.3 38.7 48.8 54.6 57.6 7 61.8 59.1 54.8 72.5 60.0 59.5 63.6 66.1 46.8 44.4 8 45.5 51.1 50.3 49.9 28.8 55.4 56.6 53.1 68.4 53.2 9 53.5 42.1 53.8 48.5 47.7 50.4 50.7 54.5 60.7 47.7
Batch 3
10 48.2 52.2 52.4 40.6 55.5 53.5 50.2 47.0 49.9 48.7 11 45.4 43.2 42.6 53.5 38.4 40.4 41.2 48.8 44.3 43.6 12 51.8 35.2 47.8 40.0 41.9 45.3 42.4 59.0 34.0 36.1 13 64.1 48.9 40.9 57.8 51.2 38.5 39.2 42.7 39.5 36.8
Batch 4
14 39.4 41.5 50.1 41.6 39.8 41.2 56.6 48.6 43.5 40.6 Descriptive Statistics Mean, x = 46.07 N/mm2 Median = 45.01 N/mm2 Mode = NA Standard deviation, s = 8.55 N/mm2 Maximum = 72.5 N/mm2 Minimum = 27.1 N/mm2 Range, R = 45.4 N/mm2 Coefficient of variation, c.v. = 18.5 %
112
Table 5.2: Compressive strength of specimens in each sample for facing
bricks tested on stretcher face Sample Compressive strength of specimens N/mm2
1 39.3 39.4 34.8 38.9 39.4 37.1 36.9 36.8 37.0 33.4
Batch 1 2 33.8 26.8 33.5 32.6 28.9 38.0 31.4 27.9 30.9 27.0
3 35.3 37.7 43.5 34.0 34.4 29.7 22.5 34.4 35.0 35.4 Batch 2 4 34.4 35.7 33.2 40.2 34.5 35.3 37.7 43.5 34.0 27.5
5 40.9 49.5 44.6 45.3 38.9 44.8 44.0 35.6 55.0 43.0 Batch 3 6 37.9 28.3 33.7 38.0 34.0 47.8 37.5 37.9 35.1 36.9
7 22.2 31.3 45.5 37.8 25.9 30.0 32.7 30.1 27.8 24.0 Batch 4 8 28.9 23.8 26.5 25.6 25.3 27.9 29.7 30.9 30.9 34.4
Descriptive Statistics Mean, x = 34.74 N/mm2 Median = 34.49 N/mm2 Mode = 35.27 N/mm2 Standard deviation, s = 6.45 N/mm2 Maximum = 55.0 N/mm2 Minimum =22.2 N/mm2 Range, R = 32.8 N/mm2 Coefficient of variation, c.v. = 18.6%
Table 5.3: Compressive strength of specimens in each sample for
facing bricks tested on header face. Sample Compressive strength N/mm2
1 9.5 9.3 9.0 9.2 8.0 8.4 7.9 9.2 8.8 9.1
Batch 1 2 2.7 4.0 3.5 3.9 2.3 4.5 3.6 3.1 4.3 4.2
3 5.0 4.3 4.6 2.2 4.6 6.9 4.7 4.7 5.4 2.5 Batch 2 4 5.4 5.4 5.1 6.2 4.1 5.0 4.3 4.6 5.1 4.6
5 10.6 5.6 4.3 7.2 5.5 11.4 7.6 6.7 6.1 7.6 Batch 3 6 4.5 5.6 3.9 4.7 4.2 5.0 4.7 3.2 3.0 6.9
7 5.5 2.4 3.2 3.7 5.6 3.2 4.3 5.6 0.8 3.0 Batch 4 8 8.4 8.9 5.5 6.0 7.3 6.4 6.1 6.9 4.8 5.8
Descriptive Statistics Mean, x = 5.51 N/mm2 Median = 5.07 N/mm2 Mode = 5.03 N/mm2 Standard deviation, s = 2.15 N/mm2 Maximum = 11.4 N/mm2 Minimum = 0.8 N/mm2 Range R =10.06 N/mm2 Coefficient of variation, c.v. =39.0 %
The descriptive statistics consisting of the mean, median, mode, standard
deviation, range and coefficient of variation were shown in Table 5.1, 5.2 and 5.3.
The mean compressive strength was 46.1, 34.7 and 5.51 N/mm2 when tested on bed,
stretcher and header face respectively. With a mean strength of 46 N/mm2 when
tested on the bed face, the bricks from this research easily surpass the top range of
113
the specified limits for ASTM, AS and the SS with exception of the Engineering
category of the BS (Table 5.8).
Data distribution was presented by the histograms as shown in Figure 5.1.
The histogram could be seen to represent a normally distributed data and in virtue of
the central limit theorem the histogram would eventually form a normal curve with
increasing number of data. Hence, assuming data to be normally distributed the
normal curve fit (Table 5.4) was computed for the compressive strengths tested on
the bed and stretcher face (having c.v.’s of 18.5 % and 18.6 % respectively). With
respect to the bricks tested on the header face the c.v. was 39.0 % which was greater
than 30 %. Therefore, the compressive strengths tested on the header face were fitted
with a log-normal curve (Table 5.5). The normal and log-normal curves were plotted
superimposed on the histograms as shown in Figure 5.1.
Table 5.4: Normal curve fit for compressive strength of facing bricks tested
on bed and stretcher face Testing
orientations Interval midpoint
x
Observed frequency
Number of standard
deviations, z (x - x) s
( )f z =
( ) ( )π -1 2 22 exp - z 2
Computed frequency ordinate, y
( )nif z s 29.269 6 -1.966 0.0577 4.2918 33.807 9 -1.435 0.1424 10.587 38.345 24 -0.904 0.265 19.701 42.883 31 -0.373 0.3721 27.655 47.421 23 0.1576 0.394 29.285 51.959 23 0.6886 0.3147 23.392 56.497 12 1.2195 0.1896 14.096 61.035 7 1.7505 0.0862 6.4072 65.573 3 2.2814 0.0296 2.197 70.111 1 2.8124 0.0076 0.5683
Bed face
74.649 1 3.3433 0.0015 0.1109 23.642 4 -1.727 0.0898 3.6622 26.925 11 -1.217 0.1902 7.7552 30.208 11 -0.707 0.3106 12.6652 33.491 18 -0.198 0.3912 15.9513 36.774 18 0.312 0.3799 15.4933 40.057 7 0.822 0.2846 11.6054 43.340 6 1.331 0.1644 6.7041 46.623 3 1.841 0.0732 2.9866 49.906 1 2.351 0.0252 1.0261 53.189 0 2.861 0.0067 0.2719
Stretcher face
56.472 1 3.370 0.0014 0.0556
114
Table 5.5: Log-normal curve fit for compressive strength of facing
brick tested on header face Interval midpoint
x
Observed frequency
Number of standard
deviations, z ( ) -1ln x - α β
( )f z =
( )( )
-0.5 -1
2
2π β
exp - z 2 - βz - α
Computed frequency ordinate, y
ni f(z)
1.034 1 -4.253 0.000 0.010 2.101 4 -2.370 0.030 2.594 3.168 9 -1.280 0.147 12.587 4.235 22 -0.509 0.220 18.759 5.302 17 0.088 0.199 16.988 6.369 9 0.575 0.141 12.035 7.436 6 0.986 0.088 7.478 8.503 5 1.342 0.051 4.321 9.570 5 1.656 0.028 2.398 10.637 1 1.937 0.015 1.303 11.704 1 2.190 0.008 0.701
From the normal and log-normal probability functions the 33-percentile
values for all the three cases of loadings were determined and are shown in Figures
5.1 (a), (b) and (c). The high and low values were meant for the upper and lower 33-
percentile while the medium values were for the middle third distribution. The upper
33-percentile for bricks tested on the bed face i.e. about one-third of the distribution
had compressive strengths exceeding 50 N/mm2 i.e. the minimum requirements for
Engineering B bricks of the BS.
The mean compressive strength representative of the population of bricks in
the study was computed after examining the homogeneity of data using the control
charts for means and ranges of samples (Figure 5.2). Data not complying with the
homogeneity criteria as explained in Chapter IV were not taken into account when
determining the population mean. In this case the control charts showed that data
from samples 4 and 7 of the bed face compressive strengths, 5 and 8 of the stretcher
face and 1, 2, 5 and 7 of the header face were lying outside the upper and lower
action lines and thus data from these samples were ignored for the computation of
population mean.
115
0
5
10
15
20
25
30
35
27.0
00-3
1.53
8
31.5
38-3
6.07
6
36.0
76-4
0.61
4
40.6
14-4
5.15
2
45.1
52-4
9.69
0
49.6
90-5
4.22
8
54.2
28-5
8.76
6
58.7
66-6
3.30
4
63.3
04-6
7.84
2
67.8
42-7
2.38
0
72.3
80-7
6.91
8
Compressive Strength, N/mm2Fr
eque
ncy
(a) Bed face
0
5
10
15
20
22.0
0-25
.283
25.2
83-2
8.56
6
28.5
66-3
1.84
9
31.8
49-3
5.13
2
35.1
32-3
8.41
5
38.4
15-4
1.69
8
41.6
98-4
4.98
1
44.9
81-4
8.26
4
48.2
64-5
1.54
7
51.5
47-5
4.83
54 8
3-58
.113
Compressive strength, N/mm2
Freq
uenc
y
(b) Stretcher face
0
5
10
15
20
25
0.50
0-1.
567
1.56
7-2.
634
2.63
4-3.
701
3.70
1-4.
768
4.76
8-5.
835
5.83
5-6.
902
6.90
2-7.
969
7.96
9-9.
036
9.03
6-10
.103
10.1
03-1
1.17
11.1
7-12
.237
Compressive strength, N/mm2
Freq
uenc
y
(c) Header face
Figure 5.1: Histogram, normal and log-normal curve for compressive
strength of facing bricks tested on (a) bed face (b)
stretcher face (c) header face
2
2
2
2
5.5 /2.15 /
. . 39.0%5.1 /
mod 5.0 /
x N mms N mmc vmedian N mm
e N mm
===
==
Low < 42.0 N/mm2 Medium 42.0 – 50.0 N/mm2 High > 50.0N/mm2
Low < 33.0 N/mm2 Medium 33.0 – 37.0 N/mm2 High > 37.0N/mm2
Low < 4.0 N/mm2 Medium 4.0 – 6.0 N/mm2 High > 6.0N/mm2
Log-normal curve
Normal curve
Normal curve
2
2
2
2
34.7 /6.45 /
. . 18.56%34.5 /
mod 35.3 /
x N mms N mmc vmedian N mm
e N mm
===
==
2
2
2
46.1 /8.55 /
. . 18.55%45.0 /
mod
x N mms N mmc vmedian N mm
e NA
===
==
116
30
40
50
60
70
0 5 10 15
Sample
Com
pres
sive
stre
ngth
Mea
n
20253035404550
0 5 10
Sample
Com
pres
sive
stre
ngth
M
ean
2
4
6
8
10
0 5 10
Sample
Com
pres
sive
stre
ngth
M
ean
01020304050
0 5 10 15
Sample
Com
pres
sive
stre
ngth
Ran
ge
0
10
20
30
40
0 5 10
Sample
Com
ress
ive
stre
ngth
sR
ange
0
2
4
6
8
0 5 10
Sample
Com
pres
sive
stre
ngth
Ran
ge
(a) Bed face (b) Stretcher face (c) Header face
UAL – Upper action line UWL –Upper warning line LAL – Lower action line LWL – Lower warning line
Figure 5.2: Control charts of mean values and ranges for compressive strength tested on (a) bed face
(b) stretcher face (c) header face
UAL
xUWL
LWL LAL
UAL UWL x LWL LAL
UAL UWL
LWL LAL
x
UAL
UWL
x LWL LAL
UAL UWL
x LWL LAL
UAL UWL x
LAL LWL
117
The ANOVA for compressive strengths tested on the different orientations
were carried out on the remaining samples. From the ANOVA, shown in Table 5.7
Fcal. for all cases were found greater than Fcrit and therefore, the N.H. was rejected
indicating that there was significant difference in the variances of the various
samples. The ANOVA from Table 5.7 also gave the components of variance, which
were used to determine the population mean. Detail explanation of the procedures
for the determination of variance from ANOVA and derivation of population mean
is shown in Chapter IV. The estimate of variances for the different orientations of
loading were 54.40, 28.32 and 10.757 tested on bed, stretcher and header face
respectively.
Table 5.6: ANOVA and variance components for compressive strengths of
facing bricks tested on bed, stretcher and header faces Testing
orientations Source of Variation
Sum of Squares
(SS)
Degree of
freedom
(df)
Mean Square
When the N.H. is accepted the mean square is an estimate of
When the N.H. is
rejected the mean square is an estimate
of
calc.F crit.F
(1) (2) (3) (4) (5) (6) (7) (8) Between samples 1672.023 11 152.002 2σ 2 2
rcσ σ+
Within samples 4704.06 108 43.556 2σ 2σ
Bed face
Total 6376.082 119 53.58 Best estimate of
2σ
3.489 1.878
Between samples 398.699 5 79.740 2σ 2 2
rcσ σ+
Within samples 1220.659 54 22.605 2σ 2σ Stretcher
face
Total 1619.358 59 27.447 Best estimate of
2σ
3.528 2.386
Between samples 29.687 3 9.896 2σ 2 2
rcσ σ+
Within samples 46.151 36 1.282 2σ 2σ Header face
Total 75.839 39 1.945 Best estimate of
2σ
7.719 2.866
The corresponding mean compressive strengths for the population tested on
bed, stretcher and header face were in the range of 40 to 51 N/mm2, 30 to 38 N/mm2
and 4.1 to 6.2 N/mm2.
118
Comparisons with other standards shows that the population mean, like the
sample mean supersedes the top range compressive strengths of ASTM, AS and SS.
However, the population did not fit in the category of Engineering A and B of the
BS which requires a minimum compressive strength of 70 N/mm2 and 50 N/mm2
respectively.
Results from the tests clearly demonstrated that a considerable amount of
compressive strength reduction occurred with increased slenderness ratio for the
bricks orientations. Samples results show that a maximum strength of 46 N/mm2
was achieved when brick was tested on its bed face. When tested on the header face
the compressive strength was less than 20 % of that on bed face. Similarly, the
compressive strength when tested on the stretcher face reduced to 34.74 N/mm2, i.e.
a reduction by about 20 % in comparison to bed face.
These results, showing the relative compressive strength reduction
corresponding to the different orientations of testing were approximately in
agreement with the study reported by Hendry (1997). Hendry showed that, bricks
tested on the stretcher and header faces produced compressive strength of about 80
% and 20 % respectively of the strength when tested on the bed face (Table 2.1).
The reduction in compressive strength was due to the effects of platen
restraint, which imposed a degree of confinement to the specimens, the greater the
height of specimen during testing the lesser was the platen effects. In the Australian
Standard the effect of platen restraint are being considered by multiplying the
compressive strength with a factor depending on the height to thickness ratio
(Table 2.2) and it diminishes at height to thickness ratio of 5 and above.
A relationship between compressive strength and height to thickness ratio
was developed in this study. The mean values ( x ) for the three orientations of
testing i.e. on bed (46.1 N/mm2), stretcher (34.7 N/mm2) and header faces (5.5
N/mm2) were plotted against the height to thickness ratio as shown by the graph in
Figure 5.3. The value of the height to thickness ratio (h/t) was based on the mean
measurements of both dimensions for samples used in the study. The graph for the
119
compressive strength versus h/t ratio was plotted and joined with a best fit line
described by equation 5.1 with a regression coefficient of R2 = 0.998
16.353 58.168f x= − + …(5.1)
Where,
f = compressive strengths in N/mm2
x = ratio of height to thickness (h/t).
Where,
h = the height in relation to the orientation of tests
t = the smallest dimension of the loaded face.
This relationship was derived specifically for standard format bricks with 5
rectangular slots. The equation can also provide estimation on the compressive
strength of bricks for the same standard format made from the same material or
comprised of the same amount of perforations. In this respect, the perforations are
rectangular with an average area of 3375 mm2 i.e. about 16 % of the total gross area.
The results could also be used to estimate the compressive strength of the same brick
format with circular holes as generally used in other manufacturing, however the
prediction is expected to be conservative in view that shearing will occur at higher
levels at failure.
f = -16.353x + 58.168R2 = 0.998
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5 3 3.5Height to thickness ratio, h/t
Com
pres
sive
stre
ngth
, fN
/mm
2
Figure 5.3: Relationship between compressive strength and h/t ratio of bricks
Bed face h/t = 0.7
Stretcher face h/t =1.5
Header face h/t =3.2
120
The calculation for compressive strength specified in standards could either
be based on the net or gross area of loaded face. Australian Standard uses the net
area i.e. gross area less the area of perforations while ASTM specifies that the
compressive strength to be calculated using gross area. BS specified the area used in
the calculation as the overall dimension.
Compressive strengths of bricks tested on bed face determined using net area
i.e. the mean area of bed face less the area of the 5 rectangular slots is shown in
Table 5.7. The mean compressive strength was 54.4 N/mm2, which indicates an
increase of about 20 % compared to values obtained using the gross area. The
population mean was in the range of 50 to 60 N/mm2. Thus, taking into account the
net area resulted in a higher value, which qualifies the bricks as Engineering B of the
BS.
Table 5.7: Compressive strengths of facing brick tested on bed face as
computed from net areas Sample Compressive strength based on net area, N/mm2
1 49.9 55.2 51.8 56.3 45.0 45.1 41.7 50.0 39.4 47.0
Batch 1 2 57.7 51.0 52.9 51.6 59.5 60.9 61.4 65.1 52.7 64.1
3 41.8 49.9 53.3 42.1 36.6 54.3 48.0 41.8 50.7 42.9 4 43.4 48.5 57.6 45.4 36.1 35.0 32.1 45.1 42.1 35.2 5 66.9 48.2 68.1 49.2 40.2 55.2 61.6 69.9 47.2 49.6
Batch 2
6 46.9 45.9 54.0 57.5 47.6 51.1 45.5 57.8 65.2 68.3 7 73.3 70.0 64.8 86.5 71.2 70.5 75.7 78.6 55.5 52.5 8 53.8 60.5 59.6 59.1 34.2 65.8 67.2 63.1 81.5 63.1 9 63.7 49.9 63.6 57.2 56.7 59.7 60.2 64.7 72.1 56.3
Batch 3
10 57.2 62.1 62.1 48.1 65.9 63.5 59.4 55.8 59.2 57.7 11 53.8 51.2 50.5 63.6 45.4 48.1 48.8 58.1 52.8 51.6 12 61.4 41.3 57.0 47.3 49.6 53.8 50.2 70.0 40.0 42.4 13 76.1 58.0 48.4 68.9 60.6 45.5 46.1 50.6 46.7 43.7
Batch 4
14 20.0 49.5 60.3 49.2 47.1 48.8 67.6 58.0 51.6 48.0 Descriptive Statistics Mean, x = 54.4 N/mm2 Median = 53.5 N/mm2 Mode = NA Standard deviation, s = 10.62 N/mm2 Maximum = 86.5 N/mm2 Minimum = 20.0 N/mm2 Range, R = 66.5 N/mm2 Coefficient of variation, c.v. = 19.5 %
121
A relationship between compressive strength with h/t ratio considering net
loaded area for the bed face orientation is shown in Figure 5.4. The relationship
shows an increase of about 13 % in the compressive strength compared to the results
obtained by considering gross area of the bed face. Thus, the relationship of
compressive strength to h/t ratios given by equation 5.1 for perforated bricks is
considered as conservative.
f = -19.187x + 66.07R2 = 0.9913
0102030405060
0 0.5 1 1.5 2 2.5 3 3.5
Height to thickness ratio, h/t
Com
pres
sive
stre
ngth
, fN
/mm
2
Figure 5.4: Relationship between the computed compressive strength
(based on net loaded area of bed face) to h/t ratio
It should be noted that in this study compressive strength tests were carried
out after the test for water absorption. In this case, the bricks were in a saturated
condition and research has shown that wet bricks tend to show lower strengths than
dry ones. Grimm, (1975), reported that dry brick can be 15% stronger than wet ones.
Some compressive tests done on dry bricks in this study also showed that the dry
bricks had strengths of about 15 to 20 % higher than the wet bricks.
The tests conducted on wet bricks based on gross area yield lower
compressive strengths as the effects of curing and gross loaded area contribute to
both physical and theoretical determination of strength. Consequently, the evaluation
of compressive strength of bricks studied in this research implies conservative
results compared to values stated in ASTM.
Bed face h/t = 0.7
Stretcher face h/t = 1.5
Header face h/t = 3.2
122
Table 5.8: Compressive strength of facing and common bricks and standard requirements
Compressive strength from research results BS (Mean of 10
bricks) ASTM (Mean of
5 bricks) AS
(Characteristic strength)
SS (Mean of 10 bricks)
Mean Engineering Ratio of manufacturing height to width
Testing orientations Population
µ
Sample x
High (Upper 33-percentile)
Normal (Middle 33-percentile)
Low (Lower 33-percentile) A B Others
SW
MW
NW
≤ 0.7 ≥ 2
Firs
t gra
de
Seco
nd g
rade
Thi
rd g
rade
Bed face . 67 0.7
98ht= ≈
40.0 – 51.0 46.00 >50.0 42.0 – 50.0 <42.0 ≥ 70
≥ 50 ≥ 5
Not less than 20.7
Not less than 17.2
Not less than 10.3
Not less than 7.0
Not less than 5.0
Not less than 35.0
Not less than 20.0
Not less than 5.2
Stretcher face 98 1.567
ht= ≈
30.0 – 38.0 34.7 >37.0 33.0 – 37.0 <33.0
Facing brick
Header face 216 3.267
ht= ≈
4.12 – 6.20 5.5 >6.0 4.0– 6.0 <4.0
Common bricks
Bed face 30.0 – 40.0 35.7 >40.0 32.0 – 40.0 <32.0
123
Results for compressive strength of common bricks are shown in Table 5.9.
In this study common bricks were referred to bricks for general building works with
no aesthetic application
Table 5.9: Compressive strength of specimens in each sample for common
bricks Sample Compressive strength determined from net area, N/mm2
1 38.5 39.5 29.0 40.0 31.1 36.1 25.2 39.4 27.8 34.0 2 39.6 38.0 36.1 27.2 39.5 33.5 25.1 36.3 34.2 32.3
Batch
1 3 38.8 37.7 29.3 38.9 26.5 36.5 25.1 37.8 27.8 34.0 4 28.5 25.9 22.5 25.2 22.7 24.7 21.3 24.4 20.1 22.2 5 21.0 27.2 39.1 39.0 33.7 32.9 35.4 31.7 39.2 40.2 Batch
2 6 20.6 26.2 19.0 25.3 23.1 24.6 20.7 36.2 18.4 21.7 7 29.6 37.9 26.8 30.8 28.6 33.6 31.7 21.2 20.2 46.0 8 41.6 42.8 36.4 38.4 41.4 48.6 49.8 39.6 43.6 40.9 Batch
3 9 34.1 38.4 36.7 35.7 40.5 47.3 49.0 36.9 45.5 40.9 10 51.4 58.0 51.7 49.2 50.4 49.1 47.0 46.7 47.2 34.2 11 38.4 44.1 44.4 38.1 49.1 45.2 48.9 39.6 48.2 33.1 Batch
4 12 48.6 34.6 44.5 25.8 41.9 50.1 45.0 43.7 41.6 34.2 Descriptive Statistics Mean, x = 35.71 N/mm2 Median = 36.42 N/mm2 Mode = 40.86 N/mm2 Standard deviation, s = 9.06 N/mm2 Maximum = 58.0 N/mm2 Minimum = 18.4 N/mm2 Range, R = 39.6 N/mm2 Coefficient of variation, c.v. = 25.4 %
0
5
10
15
20
25
30
18.3
5-22
.35
22.3
5-26
.35
26.3
5-30
.35
30.3
5-34
.35
34.3
5-38
.35
38.3
5-42
.35
42.3
5-46
.35
46.3
5-50
.35
50.3
5-54
.35
54.3
5-58
.35
Compressive strength N/mm2
Freq
uenc
y
Normal curve
Figure 5. 5: Histogram and normal curve for compressive strength of
common bricks
2
2
2
2
35.7 /9.06 /
. . 25.38%36.4 /
mod 40.9 /
x N mms N mmc vmedian N mm
e N mm
===
==
Low < 31.87 N/mm2 Medium 31.87 – 39.50 N/mm2 High > 39.50 N/mm2
124
The histogram and the normal curve fit is shown in Figure 5.5. The sample
mean was 36 N/mm2, which lie within the ranges specified for structural bricks of
ASTM for the category of SW bricks and just exceed the minimal requirement
specified of First Grade brick in Singapore Standard. However, from the normal
curve function the middle 33-percentile comprises of strengths in the range of 31.9
to 39.5 N/mm2 exceeding values for the top range of the structural bricks of ASTM
(Table 5.7).
The quality control charts (Figure 5.6) shows that 5 out of 12 samples lie
outside the upper and lower action lines thus indicating considerable scatter of
compressive strengths. This is in contrast with the results observed for facing bricks.
The wide scatter of data for common bricks shows lacking of production control.
However, it must be borne in mind that some of the common bricks were rejected
products of facing brick, therefore the properties might not be consistent with actual
common bricks production.
The population mean was derived after ignoring these 5 data points. The
variance from the ANOVA was 48.55 from which the standard deviation of the
population is estimated as 6.968 N/mm2. The population mean range computed
using this standard deviation was 30.38 to 40.34 N/mm2 and this value exceeds the
requirements for SW bricks of ASTM. and Second grade bricks of the Singapore
Standard.
The compressive strength ranged from 30 to 40 N/mm2, therefore the
common bricks in this study suffice the requirements for structural bricks under the
classification of SW bricks of the ASTM. The common bricks investigated in this
study could be used as load-bearing applications although not suitable for facing
brickwork due to lacking of other physical and dimensional properties. Previous
research on common bricks of the same manufacturer’s product showed water
absorption exceeding 10%.
125
20,0
30,0
40,0
50,0
0 2 4 6 8 10 12 14
Sample
Com
pres
sive
stre
ngth
M
ean
0,0
10,0
20,0
30,0
40,0
0 2 4 6 8 10 12 14
Sample
Com
pres
sive
stre
ngth
Ran
ge
UAL
UWL
xLWLLAL
Figure 5.6: Control charts of mean values and ranges of samples for
compressive strength of common bricks
5.3 Dimensional Tolerance
5.3.1 Overall Dimensions of 24 Bricks
Table 5.10 shows the results of overall dimension of length, width and height
of 24 bricks and the deviations of these dimensions from the work sizes for the
individual brick. These deviations were derived from the results of the overall
dimensions as shown in Table 5.10 columns (4), (6) and (8). The work sizes were as
given in the BS for length, width and height i.e. 215 mm, 102.5 mm and 65 mm
respectively. The mean value of overall length was 5218 mm, which is within the
limits of BS i.e. 5085 mm to 5235 mm. The mean value of overall width of
2412 mm was slightly out of range compared to the BS limits of 2415 mm to 2505
mm. The height had a mean value of 1642 mm, exceeding the limit of BS by 37 mm.
UAL UWL xLWL LAL
126
Table 5.10: Overall measurement of length, width and height of 24 bricks
and individual brick dimensional deviations from work size
Sam
ple
Overall Length of 24
bricks
Deviations of Individual
length of brick from work
size [(3)÷ 24]- 215
Overall width of
24 bricks
Deviations of individual width
of brick from work size
[(5)÷ 24]- 102.5
Overall height of 24
bricks
Deviations of individual
height of brick from work size
[(7)÷ 24]- 65 (2) (3) (4) (5) (6) (7) (8) 1 5240 3.33 2415 -1.88 1638 3.25
(1)
Batch 1
2 5254 3.92 2410 -2.08 1646 3.58 3 5216 2.33 2408 -2.17 1648 3.67 4 5263 4.29 2426 -1.42 1651 3.79 5 5241 3.38 2421 -1.63 1650 3.75
Batch
2 6 5243 3.46 2419 -1.71 1653 3.88 7 5175 0.63 2405 -2.29 1628 2.83 8 5218 2.42 2412 -2.00 1640 3.33 9 5185 1.04 2413 -1.96 1625 2.71
Batch
3 10 5178 0.75 2397 -2.63 1634 3.08 11 5203 1.79 2416 -1.83 1638 3.25 12 5211 2.13 2400 -2.50 1643 3.46 13 5210 2.08 2409 -2.13 1643 3.46
Batch
4 14 5213 2.21 2414 -1.92 1644 3.50
Descriptive statistics Mean, x 5218 2.41 2412 -2.01 1642 3.40 Median 5215 2413 1643 Mode #N/A #N/A 1638 Standard deviation, s 27.55
7.86
8.35
Maximum 5263 2426 1653 Minimum 5175 2397 1625 Range, R 88 29 28 c.v. 0.53% 0.33% 0.51%
Max. Min. Max. Min. Max. Min. British Standard 5235 5085 2505 2415 1605 1515 Note: Work sizes as in BS 3921:1985 – Length = 215 mm, width = 102.5 mm, height = 65 mm
A plot of sample overall dimensions against specified limits of BS and SS is
shown in Figure 5.7. The SS provides three grades of dimensional tolerance i.e. first,
second and third grade, depending on the degree of dimensional accuracy required,
however bricks under the category of the third grade are not limited to any
dimensional tolerance.
Figure 5.7 clearly demonstrates that the bricks in this research had lengths
and widths marginally in agreement with the BS and SS first grade bricks but the
height was oversize. The length belongs to the higher range of the BS as evident by
127
5 samples lying outside the upper range [Figure 5.7 (a)], while the width were in the
lower range of the BS with 5 samples lying below the lower range of the width
measurement [Figure 5.7 (b)]. On the other hand, all samples for the height exceeds
the maximum limit of the British Standard.
5000
5100
5200
5300
5400
5500
0 5 10 15 20
Sample
Ove
rall
Len
gth
(mm
)
(a)
2350
2400
2450
2500
2550
2600
0 5 10 15 20
Sample
Ove
rall
Wid
th (m
m)
BS and SS First Grade
SS Second Grade
(b)
1460
1510
1560
1610
1660
1710
1760
1810
0 5 10 15 20Sample
Ove
rall
Hei
ght (
mm
)
BS SS First Grade
SS Second Grade
(c)
Figure 5.7: Comparison of overall dimensions of (a) length (b) width and
(c) height with allowable range of British and Singapore Standard.
SS Second Grade
BS and SS First Grade
128
The dimensional tolerance of the bricks investigated in this research was also
evaluated against values of tolerances provided in the European Standard
prEN 771-1 and the derived tolerance limit for individual brick based on the
cumulative measurement of 24 bricks. Table 5.11 shows the comparisons of
dimensional tolerances for individual brick from results of this research (col. 2) with
values derived from specified tolerance for 24 bricks of BS 3921 (col.5) and the
tolerance categories of T1 and T2 in prEN 771-1 (col. 3 and 4). In the prEN 771-1
the mean dimensions of 10 bricks in a sample should not differ from the declared
value of either categories T1 and T2, which correspond to the following:
T1: 0.4 (work size dimension)± mm or 3 mm whichever is greater.
T2: 0.25 (work size dimension)± mm or 2 mm whichever is greater.
The dimensional deviations for individual brick derived from BS 3921
(col.5), was calculated based on the limits given for the overall dimensions of 24
bricks. For example, the overall length of 24 bricks should not exceed 5235 mm and
not less than 5085 mm, which equal to a tolerance of 6.25 mm or 3± .125 mm for
the length of individual brick.
Table 5.11: Dimensional deviations of brick from work size and comparisons
with values of dimensional tolerance for BS 3921:1985 and prEN
771-1
prEN 771-1 Dimensional tolerance for BS work
size.
Dim
ensi
ons
Test results of mean dimensional deviations from work size derived from measurement of
24 bricks (mm) (From Table 5.10) T1
(mm) T2
(mm)
BS 3921 Individual brick deviations from
work size derived from
tolerances of 24 bricks
(1) (2) (3) (4) (5)
Len
gth
+ 2.41 0.4 215 5.9± = ±
0.25 215 3.7± = ±
3.125±
Wid
th
- 2.01
0.4 102.5 4.0± = ±
0.25 102.5 2.5± = ±
1.875±
Hei
ght
+ 3.4 0.4 65 3.2± = ± 0.25 65 2.0± = ±
1.875±
129
Therefore, from the comparisons of individual bricks dimensional tolerance
of prEN 771-1 and BS 3921 it could be observed that the dimensional tolerance for
individual bricks derived from BS tolerance for 24 bricks is more stringent than the
prEN 771-1 for both the T1 and T2 categories. Research results showed that the
mean deviations of the dimensions of bricks from the work size (Table 5.11, col. 2)
for length i.e. +2.41 mm was within the derived deviation of the BS (± 3 mm)
however the width and height had a deviation of –2.01 mm and +3.4 mm which
exceeded the deviations i.e. 1.875± for both width and height. Nevertheless, it
should be borne in mind that the strict dimensional deviations provided in the British
Standard was derived from the cumulative dimensions of 24 bricks. Moreover, these
deviations are restricted to bricks of the standard format specified in BS 3921.
Table 5.11 shows that the bricks investigated fulfil the requirements for category T1
of the dimensional tolerance specified in the prEN 771-1. The bricks however could
not satisfy the tolerance limit for category T2 due to the height exceeding the range
specified for the T2 category.
5.3.2 Dimension of Individual Brick for Length, Width and Height
Table 5.12 shows sample data with the mean, ranges, standard deviations,
and coefficient of variation for length, width and height of individual brick. The
mean for length, width and height were 216 mm (s =1.91 mm), 100 mm (s =1.12
mm) and 67 mm (s =1.91 mm) respectively and the normal values which is in the
middle third of the 33-percentile values were 216 to 218 mm for length, 98 to100
mm for width and 67 to 68 mm for height (Figure 5.8).
130
Table 5.12: Individual brick dimensions for length, width and height in all samples Length Width Height
Sample Mean
x
Range
R
Standard deviation
s
c.v. %
Mean
Range
R
Standard deviation
s
c.v. %
Mean
x
Range
R
Standard deviation
s
c.v. %
1 218.4 1.6 0.57 0.26 100.2 2.4 0.81 0.81 67.1 1.2 0.41 0.62 2 218.4 2.6 0.94 0.43 99.8 1.9 0.78 0.78 67.2 1.6 0.68 1.02 3 216.6 6.2 2.12 0.98 99.0 2.2 0.94 0.95 67.5 2.6 0.91 1.35 4 218.0 2.7 1.00 0.46 99.6 1.1 0.37 0.37 67.2 5.5 2.05 3.04 5 216.6 1.5 0.61 0.28 99.0 2.5 0.95 0.96 66.4 1.1 0.39 0.59 6 217.7 2.8 0.99 0.45 99.8 1.8 0.80 0.80 67.2 1.1 0.44 0.65 7 217.7 2.8 1.13 0.52 100.0 1.9 0.66 0.66 67.9 1.0 0.42 0.62
Batch 1
8 219.1 3.2 1.36 0.62 99.9 2.3 0.81 0.81 68.0 2.0 0.82 1.21 9 216.6 4.1 1.62 0.75 99.9 4.4 1.64 1.64 68.2 4.3 1.45 2.13
10 215.5 10.5 3.63 1.68 99.3 4.1 1.43 1.44 67.8 3.4 1.19 1.75 11 216.1 3.9 1.57 0.72 99.3 2.4 0.95 0.95 68.1 2.5 0.83 1.22 12 216.4 5.8 2.29 1.06 98.9 4.8 1.82 1.84 67.7 2.5 0.83 1.22 13 218.0 6.5 2.72 1.25 100.4 4.3 1.57 1.56 68.2 2.0 0.65 0.95 14 217.7 3.7 1.67 0.77 100.3 2.8 1.16 1.15 67.3 1.9 0.86 1.28 15 217.7 6.2 2.16 0.99 99.8 3.7 1.39 1.39 67.7 1.7 0.73 1.08 16 218.8 4.5 1.77 0.81 100.7 3.9 1.52 1.51 68.8 4.3 1.42 2.06 17 216.8 1.7 0.73 0.34 99.8 2.2 0.88 0.88 67.6 1.6 0.62 0.91 18 219.0 2.6 0.94 0.43 100.9 1.2 0.44 0.44 68.2 1.9 0.81 1.18 19 216.7 4.0 1.76 0.81 99.8 2.3 0.86 0.86 68.2 2.2 0.75 1.11 20 217.7 3.7 1.43 0.66 100.2 2.6 0.85 0.85 68.1 1.6 0.61 0.89 21 219.1 4.7 1.85 0.84 101.0 4.4 1.65 1.63 68.1 3.1 1.09 1.60 22 217.5 7.0 2.60 1.20 99.8 5.9 2.07 2.07 68.6 3.4 1.21 1.77 23 216.3 4.9 1.91 0.88 99.4 3.3 1.43 1.44 67.9 2.0 0.69 1.02
Batch 2
24 218.0 11.0 4.14 1.90 100.0 4.2 1.60 1.60 67.9 2.7 0.95 1.39
131
Table 5.12 (cont.): Brick dimensions for length, width and height in all samples. Length Width Height
Sample Mean
x
Range,
R
Standard deviation
s
c.v. % Mean
x
Range
R
Standard deviation
s
c.v. % Mean
x
Range
R
Standard deviation
s
c.v. %
25 215.7 2.1 0.98 0.46 99.7 2.3 0.89 0.89 67.2 1.1 0.37 0.55 26 214.6 2.5 0.98 0.46 99.5 1.7 0.71 0.71 66.9 1.0 0.40 0.60 27 215.1 2.2 0.89 0.42 99.8 3.2 1.22 1.22 67.1 2.0 0.67 1.00 28 214.7 3.3 1.19 0.55 99.9 1.7 0.73 0.73 67.1 1.0 0.34 0.51 29 215.4 2.3 0.80 0.37 99.7 2.2 0.79 0.79 67.4 0.6 0.25 0.38 30 216.3 2.3 0.82 0.38 100.5 1.8 0.60 0.60 67.7 0.8 0.34 0.51 31 214.7 3.9 1.33 0.62 99.4 3.3 1.13 1.14 67.4 2.6 1.03 1.52 32 215.7 2.2 0.79 0.37 100.3 2.1 0.74 0.74 67.5 1.5 0.53 0.79 33 215.2 3.1 1.26 0.59 99.4 2.3 0.97 0.97 67.4 2.9 0.94 1.40 34 215.5 2.8 1.21 0.56 100.0 0.9 0.32 0.32 67.2 1.6 0.57 0.85 35 215.1 1.8 0.72 0.34 99.0 3.0 1.13 1.15 67.0 0.4 0.11 0.17 36 215.1 2.2 0.75 0.35 98.7 1.3 0.43 0.43 67.1 1.8 0.58 0.86 37 216.1 2.3 0.80 0.37 99.8 3.0 1.08 1.08 67.0 1.1 0.38 0.57 38 215.0 1.5 0.51 0.24 99.2 1.4 0.54 0.54 66.8 1.0 0.38 0.57 39 214.8 1.4 0.57 0.26 99.6 1.4 0.61 0.62 67.0 0.6 0.20 0.30
Batch 3
40 215.2 2.2 0.94 0.44 100.2 1.4 0.49 0.49 67.1 1.3 0.44 0.65
132
Table 5.12 (cont.): Brick dimensions for length, width and height in all samples. Length Width Height
Sample
Mean x
Ranges
R
Standard deviation
s
c.v. %
Mean x
Ranges
R
Standard deviation
s
c.v. %
Mean x
Ranges
R
Standard deviation
s
c.v. %
41 216.4 1.6 0.54 0.25 100.2 1.8 0.65 0.65 67.7 1.4 0.51 0.75 42 216.2 3.4 1.24 0.57 99.8 2.8 1.03 1.03 67.5 1.4 0.49 0.72 43 215.6 2.7 1.02 0.48 99.6 3.0 1.24 1.24 67.4 1.2 0.40 0.60 44 215.1 3.5 1.46 0.68 98.9 4.3 1.64 1.66 67.1 1.9 0.74 1.10 45 215.1 3.5 1.27 0.59 98.7 3.3 1.15 1.17 67.3 1.7 0.66 0.97 46 215.7 3.3 1.12 0.52 99.4 3.2 1.18 1.19 67.4 1.6 0.62 0.93 47 215.7 3.8 1.30 0.60 99.1 2.5 1.02 1.03 66.6 2.8 1.06 1.59 48 216.2 4.9 1.81 0.84 99.2 3.2 1.32 1.33 67.6 2.9 1.12 1.66 49 216.9 5.7 2.63 1.21 100.2 4.4 1.93 1.93 67.4 1.6 0.71 1.05 50 214.6 3.2 1.18 0.55 99.0 1.7 0.62 0.62 67.0 2.2 0.71 1.06 51 216.8 6.2 2.04 0.94 100.0 3.2 1.10 1.10 67.5 1.9 0.74 1.10 52 217.0 6.9 2.37 1.09 99.7 2.2 0.79 0.79 67.0 3.3 1.06 1.59 53 215.8 4.1 1.56 0.72 100.0 1.1 0.40 0.40 68.3 2.1 0.82 1.21 54 215.4 1.6 0.59 0.27 99.5 3.1 1.00 1.00 67.2 1.1 0.37 0.55 55 216.1 2.1 0.72 0.33 100.3 1.2 0.40 0.40 67.4 1.7 0.61 0.90
Batch 4
56 216.3 1.5 0.58 0.27 99.8 1.4 0.55 0.56 67.5 0.6 0.27 0.40
133
0102030405060708090
209.
75-2
10.9
1
210.
91-2
12.0
7
212.
07-2
13.2
3
213.
23-2
14.3
9
214.
39-2
15.5
5
215.
55-2
16.7
0
216.
70-2
17.8
6
217.
86-2
19.0
2
219.
02-2
20.1
8
220.
18-2
21.3
4
221.
34-2
22.5
0
Individual length (mm)
Freq
uenc
y
Normal Curve
0102030405060708090
100
96.3
0-96
.96
96.9
6-97
.62
97.6
2-98
.28
98.2
8-98
.94
98.9
4-99
.60
99.6
-100
.26
100.
26-1
00.9
2
100.
92-1
01.5
8
101.
58-1
02.2
4
102.
24-1
02.9
0
102.
90-1
03.5
6
Individual width (mm)
Freq
uenc
y Normal curve
0
20
40
60
80
100
120
63.5
0-64
.21
64.2
1-64
.91
64.9
1-65
.62
65.6
2-66
.32
66.3
2-67
.03
67.0
3-67
.73
67.7
3-68
.44
68.4
4-69
.14
69.1
4-69
.85
69.8
5-70
.55
70.5
5-71
.26
Individual height (mm)
Freq
uenc
y
Normal curve
Figure 5.8: Histogram and normal curve for individual dimensions
of length, width and height of bricks
Control charts for the dimensions shows that all data points for the width
were lying within the upper and lower action line and showing less scatter about the
mean (Figure 5.9). All samples were then considered to represent the population
estimates for the width. For length and height, sample data lying outside the upper
and lower warning and action lines were ignored for the derivation of the population
mean.
216.4 mm1.91mm
. . 0.88 %Median= 216.2 mmMode= 215.0 mm
xsc v
===
Low <216 mm Normal 216–218 mm High >218 mm
Low < 98 mm Normal 98 – 100 mm High > 100 mm
Low < 67 mm Normal 67 – 68 mm High > 68 mm
99.7 mm1.12 mm
. . 1.12 %Median= 99.8 mmMode= 100 mm
xsc v
===
67.5 mm0.89 mm
. . 1.32 %Median= 67.4 mmMode= 67.0 mm
xsc v
===
134
214.0215.0216.0217.0218.0219.0220.0
0 10 20 30 40 50 60Sample
Len
gth
(mm
)M
ean
0.0
3.0
6.0
9.0
12.0
0 10 20 30 40 50 60
Sample
Len
gth
(mm
) R
ange
(a)
98,098,599,099,5
100,0100,5101,0101,5
0 10 20 30 40 50 60
Sample
Wid
th (m
m)
Mea
n
0,01,02,03,04,05,06,07,0
0 10 20 30 40 50 60
Sample
Wid
th (m
m)
Ran
ge
(b)
66,066,567,067,568,068,569,069,5
0 10 20 30 40 50 60
Sample
Hei
ght (
mm
)M
ean
0,01,02,03,04,05,06,0
0 10 20 30 40 50 60
Sample
Hei
ght (
mm
)R
ange
(c)
Figure 5.9: Control charts for mean values and ranges of samples for (a)
length (b) width and (c) height of bricks
The components of variances for samples from the different batches were
computed from the ANOVA. A single factor ANOVA was carried out on the
remaining samples after ignoring those outliers from the control charts. The
variances computed from the ANOVA were 1.98, 1.25 and 0.49 for length, width
and height respectively. Table 5.13 shows the comparisons of mean dimension from
results of this research with specified values of BS 3921. It could be seen that the
population mean dimensions of length i.e. 215 to 218 mm, width 99 to 101 mm and
height 67 to 68 mm were within the allowable dimensions of the BS (i.e. less than
the coordinating size for the respective length, width and height). Moreover,
individual measurements also showed that none of the bricks in the sample had
135
dimensions exceeding the specified coordinating size (Appendix A1, Table A1-1,
A1-2, A1-3)
Table 5.13: Mean dimensions of individual length, width and height of
bricks compared with British Standard (BS 3921:1985)
Mean dimensions (mm)
British standard Specification
High (upper 33-percentile)
Normal (middle 33-percentile)
Low (lower 33-percentile)
Population estimates @ 95 %
confidence (mm)
Work size (mm)
Coordinating size (mm)
Length
>218 216 – 218 < 216 215 – 218 215 225
Width >100 98 – 100 < 98 99 – 101 102.5 112.5
Height >68 67 – 68 < 67 67 – 68 65 75
5.4 Water Absorption
Table 5.14 shows specimens results for water absorption for all samples.
The descriptive statistics computed shows that the mean water absorption in
percentage was 11.23 with a standard deviation of 1.284 and c.v. of 11.43 %.
Table 5.14: Water absorption of specimens in each sample for facing bricks
Sample Water absorption of bricks (%)
1 10.6 10.2 10.9 12.7 9.5 11.6 10.8 10.6 13.7 10.5 2 8.4 13.4 10.4 8.8 9.5 11.9 10.5 8.0 11.6 12.1
Batch
1
3 10.5 11.0 11.2 11.6 10.6 11.4 10.8 13.0 12.3 11.1 4 11.6 12.6 10.7 10.8 11.6 12.0 10.8 11.3 13.4 10.6 5 11.8 12.9 12.2 13.8 11.1 10.4 12.4 11.2 12.4 10.9 6 10.8 13.1 12.4 12.4 10.9 11.5 10.0 11.9 11.3 11.2 7 12.0 11.5 10.9 11.6 11.7 12.3 12.2 13.0 13.0 11.9 8 12.4 10.4 10.1 12.4 11.6 10.7 12.0 11.5 12.3 10.5 9 11.9 12.7 11.2 9.7 11.6 11.9 11.1 12.8 13.2 12.0 10 12.0 10.4 11.6 10.0 11.7 12.8 10.3 9.4 12.2 13.6
Batch 2
11 13.1 11.5 12.7 12.1 11.0 12.3 12.2 11.1 11.8 11.5
136
Table 5.14 (cont.) 12 11.9 11.3 12.1 12.7 10.5 10.5 10.4 12.7 10.4 11.3 13 9.9 9.0 11.0 11.4 11.8 10.2 11.6 12.0 12.3 10.8 14 12.4 11.2 12.2 10.6 12.1 12.8 11.1 10.7 11.3 11.0 15 11.9 11.6 10.5 10.3 11.1 11.8 9.2 10.8 11.7 10.0 16 7.7 10.3 11.3 12.0 9.7 11.4 11.6 10.3 10.8 9.8 17 8.8 9.2 9.3 8.8 10.1 9.6 9.3 9.1 9.5 10.4 18 10.4 10.2 11.1 10.3 11.5 11.9 11.4 11.4 9.5 10.6
Batch 3
19 11.2 10.8 12.1 9.4 9.9 10.1 10.2 10.5 12.2 11.4 20 8.6 13.6 11.6 12.4 11.0 11.5 8.5 11.6 10.0 11.7 21 12.6 8.6 12.1 11.7 9.7 12.1 12.0 8.6 11.8 8.3 22 10.3 9.6 11.4 11.1 10.6 14.0 13.3 11.1 9.9 10.0 23 9.3 13.1 12.0 10.4 12.7 12.9 9.3 12.7 13.5 11.3 24 12.3 11.0 13.0 12.6 13.5 12.4 12.8 14.4 12.1 11.9 25 12.7 8.9 9.6 11.7 12.4 13.4 10.7 11.8 12.7 11.1 26 11.7 7.9 9.3 10.1 11.7 12.1 8.6 9.2 11.1 13.0
Batch 4
27 12.5 12.2 12.0 7.9 12.7 12.4 11.3 8.8 11.5 11.8 Descriptive Statistics Mean, x = 11.2 % Median = 11.4 % Mode = 12.3 % Standard deviation, s = 1.28 % Maximum = 14.4 % Minimum = 7.7 % Range, R = 6.7 % Coefficient of variation, c.v. = 11.44 %
The histogram with the normal curve superimposed to represent the data
distribution is shown in Figure 5.10.
010203040506070
7.55
-8.2
5
8.25
-8.9
5
8.95
-9.6
5
9.65
-10.
35
10.3
5-11
.05
11.0
5-11
.75
11.7
5-12
.45
12.4
5-13
.15
13.1
5-13
.85
13.8
5-14
.55
Absorption in percentage
Freq
uenc
y
Figure 5.10: The histogram and the normal curve fit for water
absorption of bricks
The 33-percentile values were computed from the normal curve. The middle
third of the distribution, which refers to the normal values of water absorption was
11 to 12 %. The control charts as shown in Figure 5.11 shows that sample 17 and
11.2 %1.28 %
. . 11.43%Median = 11.4 %Mode = 12.3 %
xsc v
===
Low < 11% Normal 11 – 12% High > 12%
Normal curve
137
24 were lying outside the upper and lower action line. Therefore, these two samples
were ignored in the determination of the population mean. The variance derived
from ANOVA was 1.53 with the standard deviation of 1.24 %. The population
mean for water absorption at 95 % confidence falls in the range of 10 to 12 %.
9,010,011,012,013,0
0 10 20 30
Sample
Wat
er A
bsrp
tion
(%)
Mea
n
0,02,04,06,08,0
0 10 20 30
Sample
Wat
er A
bsor
ptio
n (%
)R
ange
Figure 5.11: Control chart of mean values and ranges of samples for
water absorption of bricks
In most standards water absorption is often specified against compressive
strength to designate bricks classification. In conjunction with this classification the
bricks population under investigation have a mean compressive strengths of 40 to
over 50 N/mm2 with water absorption of 10 to12 %, appears to supersede the top
range of SW bricks meant for structural application in ASTM.
Table 5.15: Comparison of water absorption with limits specified by British
Standard and ASTM Water absorption %
British Standard (BS 3921) ASTM C 62 – 89a
Research results
at 95% confidence Engineering A Engineering B Grade
SW Grade MW
Grade NW
10 – 12 % ≤4.5 % ≤7.0 % Maximum
17 % Maximum 22 %
No limit
Comparison of the values for water absorption tests with limits specified in
BS and ASTM (Table 5.15) shows that water absorption of bricks for the
population in this study did not lie in the range of the Engineering A and B of the
BS. However, it can be seen that this range was within the requirements in ASTM
for bricks of the SW and MW category.
138
The British standard specifies bricks of high strength and low water
absorption for their Engineering bricks, which are meant for structural masonry.
Corresponding characteristic flexural strength to three levels of water absorption is
provided in BS 5628: Part 1 i.e. less than 7 %; between 7 % and 12 % and over 12
% to be used in designs (Table 5.16). In this respect, the water absorption
characterised by the bricks in this investigation relates to second level of water
absorption i.e. between 7 and 12 % to yield an estimated characteristic flexural
strength of 0.35 to 1.5 depending upon the mortar designation and plane of failure.
Table 5.16: Relationship between characteristic flexural strengths and levels
of water absorption (BS 5628 Pt. 1) Characteristic flexural strength , fkx N/mm2
Plane of failure parallel to bed joints
Plane of failure perpendicular to bed joints
Mortar designation
(i) (ii) and (iii) (iv) (i) (ii) and (iii) (iv)
Water absorption less than 7%
0.7 0.5 0.4 2.0 1.5 1.2
Between 7 % and 12 % 0.5 0.4 0.35 1.5 1.1 1.0
Over 12 % 0.4 0.3 0.25 1.1 0.9 0.8
A relationship between water absorption and porosity was developed for
bricks investigated in this research. The relation was a projection from results
obtained by Khalaf (2002) and is shown in Chapter VI.
5.5 Initial Rate of Suction
The initial rate of suction for bricks in this investigation was computed based
on gross and net area of immersion. In the BS, IRS is determined based on gross
area of immersion without considering the reduced area due to perforations for cored
bricks. However, in the ASTM and AS/NZS the IRS for cored bricks is calculated
based on the net area of immersion i.e. the gross area less the area of perforations
139
Table 5.17 shows the results of IRS in the specimens for all samples. The
sample mean based on gross area of immersion was 1.6 kg/m2.min. with a standard
deviation of 0.49 kg/m2.min. and a c.v. of 29.6 %.
Table 5.17: Computed values for initial rate of suction of specimens
for facing bricks based on gross area of immersion Sample IRS kg/(m2.min.)
1 1.8 1.4 1.6 1.4 2.2 1.6 2.3 0.9 1.6 1.2 2 1.4 1.6 1.4 0.9 1.6 1.6 1.4 1.2 1.4 1.8
Batch
1
3 1.4 1.6 2.6 1.2 1.9 1.6 1.6 1.6 2.1 1.6 4 1.6 1.7 1.6 1.9 2.2 1.6 1.8 1.8 1.7 1.7 5 1.7 1.8 2.0 1.4 1.7 2.0 2.1 1.7 2.1 2.3 6 1.8 1.6 1.8 1.4 2.0 2.9 1.6 1.7 1.5 1.5 7 2.0 2.0 2.0 2.0 1.7 2.2 1.9 1.7 1.8 1.8 8 2.0 2.3 2.4 2.0 1.3 1.5 1.7 1.4 1.9 2.3 9 1.9 1.3 2.0 1.7 1.6 1.6 1.4 1.1 2.0 1.9 10 1.6 1.1 1.8 2.6 1.7 1.8 1.5 1.5 1.9 1.9
Batch 2
11 2.0 1.9 1.9 2.1 2.2 0.8 1.7 1.7 1.7 1.1 12 1.4 2.0 1.2 2.0 2.1 1.4 2.0 1.6 1.5 2.3 13 1.7 1.9 1.5 1.6 2.1 1.9 1.7 1.2 1.4 2.4 14 2.0 1.6 2.1 1.8 1.3 1.9 1.6 1.9 1.6 2.5 15 1.4 1.5 2.5 1.2 2.0 1.9 1.1 1.5 2.0 1.6 16 0.1 1.0 1.8 1.1 1.2 1.5 1.4 1.5 1.0 1.8 17 2.0 1.2 1.5 1.4 1.4 1.4 1.1 1.4 1.0 0.7 18 1.1 1.5 1.1 1.0 1.8 1.0 1.9 1.7 1.2 1.7
19 1.9 1.9 1.7 1.6 1.9 1.8 1.2 1.6 1.5 1.1 20 2.1 0.6 1.1 2.0 1.8 1.6 2.0 0.7 1.2 1.9 21 1.7 0.9 2.0 2.1 0.9 2.1 0.8 1.8 1.5 1.7 22 1.9 2.1 1.6 2.1 1.5 1.3 0.4 1.5 0.6 2.7 23 1.8 2.1 1.8 1.8 0.8 1.6 2.5 0.7 2.3 1.5 24 2.5 3.1 1.5 1.6 2.3 2.1 2.4 2.5 0.8 1.1 25 2.3 0.8 2.2 2.5 2.2 1.5 2.3 1.8 0.7 2.3 26 1.2 0.2 0.6 2.2 0.8 2.3 2.5 0.9 2.4 0.9
Batch 4
27 1.1 2.3 0.9 0.2 0.9 1.9 1.3 1.0 1.1 2.2 Descriptive Statistics Mean, x = 1.6 kg/(m2.min.) Median = 1.7 kg/(m2.min.) Mode = 2.3 kg/(m2.min.) Standard deviation, s = 0.49 kg/(m2.min.) Maximum = 3.1 kg/(m2.min.) Minimum =0.1 kg/(m2.min.) Range, R = 3.0 kg/(m2.min.) Coefficient of variation, c.v. = 29.6 %
The c.v. for IRS in the samples was almost 30.0 % and therefore the log-
normal probability curve was used to represent the data distribution. Figure 5.12
shows the histogram with the log-normal curve superimposed. The 33-percentile
140
values in the sample data were computed from the log-normal probability curve and
data in the middle third i.e. 1.0 to1.30 kg/m2.min. indicated normal values for IRS.
These values were within the limits of IRS denoted to produce good bond.
01020304050607080
0.14
- 0.
417
0.41
7 - 0
.694
0.69
4 - 0
.971
0.97
1 - 1
.248
1.24
8 - 1
.525
1.52
5- 1
.802
1.80
2 - 2
.079
2.07
9 - 2
.356
2.35
6 - 2
.633
2.63
3 - 2
.910
Initial rate of suction kg/(m2.min)
freq
uenc
y
Log-normalcurve
Figure 5.12: Histogram and normal curve fit for IRS based on
gross area of immersion
1.00
1.50
2.00
2.50
0 5 10 15 20 25 30
Sample
IRS
kg/(m
2 .min
)M
ean
0.00
1.00
2.00
3.00
0 5 10 15 20 25 30
Sample
IRS
kg/(m
2 .min
)R
ange
Figure 5.13: Control charts for means and ranges for IRS based on
gross area of immersion
The control charts of means and ranges (Figure 5.13) shows that some
samples were lying outside the control limits i.e. the upper and lower warning and
action lines. Therefore, these samples i.e. samples 4, 7, 16, 17, 22, 24, 26 and 27
were taken as not representative of the population and were ignored in the
determination of the population mean. The estimate of variance derived from
ANOVA for all data after ignoring the samples described above was 0.178. The
corresponding standard deviation was 0.422 kg/m2.min.and the population mean
ranging from 1.4 to 2.0 kg/m2.min i.e. at 95 % confidence (5 % reject).
2
2
2
2
1.6 / .min0.49 / .min
. . 30.0%1.7 / .min
mod 2.3 / .min
x kg ms kg mc vmedian kg m
e kg m
===
==
Low < 1.0 kg/m2.min Normal =1.0 – 1.30 kg/m2.min High > 1.30 kg/m2.min
141
ASTM specifies that bricks with IRS greater than 1.5 kg/m2.min should be
well wetted before laying and recommended that the wetting be carried out 3 to 24
hours before use. On the other hand there is no provision of IRS limits in the BS
3921:1985. However, a test method for determining IRS is included in the British
standard as this parameter is important for highly stressed masonry structures. In
prEN 771-1 the IRS values are only required in application where the work warrant
its use and in this respect the value should be declared by the manufacturer.
Although the normal values of IRS in the middle third distribution, ranged
from 1.0 to 1.3 kg/m2.min is within the recommended limit of the ASTM the upper
range of the 95 % confidence limits were higher than 1.5 kg/m2.min. Hence,
consideration for wetting of the bricks should be emphasised especially in
application where bond strength is critical.
Wetting bricks before laying is more critical in hot weather construction
since suction rate of bricks is influenced by the temperature of the bricks and the
surrounding temperature (Davidson, 1982). Warmer units will absorb more water
from the mortar and in addition, the water from mortar is evaporated at a faster rate.
For this reason, in hot weather construction, bricks with high suction rates (over 1.5
kg/m2.min) should be well wetted before laying. On this basis, the IRS should be
regarded as an important property of brick for this country, which experience hot
weather throughout the year.
Table 5.18 shows the results for IRS based on net area of immersion. The
mean IRS was 1.9 kg/m2.min, which showed a considerable increase of about 20 %
from the IRS determined by gross area of immersion. The ASTM considers this
factor and specified that the IRS should be calculated based on the net area of
immersion for perforated bricks while the AS/NZS 4456:1997 specifies both values
of IRS due to net and gross area of immersion.
142
Table 5.18: Computed values for initial rate of suction of specimens of
facing bricks based on net area of immersion
Sample IRS kg/(m2.min.)
1 2.11 1.65 1.89 1.66 2.60 1.86 2.67 1.10 1.90 1.36 2 1.64 1.90 1.62 1.11 1.90 1.92 1.63 1.37 1.63 2.17 3 1.64 1.90 3.01 1.37 2.23 1.91 1.90 1.91 2.43 1.91 4 1.90 1.96 1.93 2.18 2.62 1.88 2.13 2.08 1.97 1.99 5 1.95 2.08 2.38 1.62 1.99 2.38 2.48 2.05 2.50 2.74 6 2.14 1.83 2.06 1.65 2.35 3.43 1.89 2.00 1.74 1.74 7 2.40 2.33 2.33 2.30 1.98 2.53 2.29 2.00 2.12 2.12 8 2.37 2.65 2.82 2.41 1.49 1.71 1.96 1.62 2.24 2.71 9 2.23 1.48 2.35 1.97 1.85 1.88 1.70 1.31 2.30 2.26 10 1.92 1.31 2.11 3.07 1.98 2.06 1.78 1.80 2.22 2.18
Batch 1
11 2.35 2.19 2.27 2.42 2.60 0.89 2.01 2.04 2.02 1.26 12 1.67 2.34 1.39 2.39 2.42 1.59 2.34 1.86 1.73 2.73 13 2.02 2.28 1.71 1.88 2.44 2.19 1.99 1.40 1.67 2.81 14 2.38 1.93 2.43 2.09 1.55 2.22 1.87 2.25 1.87 2.94 15 1.59 1.71 2.94 1.40 2.38 2.21 1.24 1.75 2.35 1.89 16 0.17 1.21 2.07 1.27 1.35 1.70 1.60 1.75 1.17 2.11 17 2.37 1.44 1.80 1.65 1.69 1.70 1.27 1.70 1.16 0.83 18 1.32 1.73 1.34 1.17 2.17 1.23 2.28 1.98 1.39 2.02
Batch 3
19 2.19 2.17 2.03 1.91 2.22 2.13 1.44 1.93 1.76 1.29 20 2.45 0.68 1.28 2.29 2.09 1.89 2.32 0.79 1.35 2.19 21 2.02 1.06 2.29 2.49 1.11 2.50 0.89 2.16 1.80 1.98 22 2.25 2.44 1.90 2.53 1.78 1.49 0.45 1.73 0.68 3.19 23 2.08 2.46 2.07 2.11 0.96 1.86 3.00 0.85 2.73 1.78 24 2.97 3.59 1.81 1.92 2.71 2.52 2.78 2.92 0.98 1.28 25 2.66 0.94 2.57 2.92 2.55 1.70 2.68 2.07 0.82 2.66 26 1.45 0.22 0.71 2.60 0.99 2.71 2.93 1.06 2.77 1.04
Batch 4
27 1.24 2.66 1.04 0.28 1.04 2.19 1.52 1.20 1.30 2.59 Mean x = 1.933 kg/(m2.min.)
5.6 Density
Table 5.19 shows the results for the density test in the specimens for all
samples. The mean density from sample data was 1781.51 kg/m3 with a standard
deviation of 35.858 kg/m3 and a c.v. of 2.013 %.
143
Table 5.19: Density of specimens in each sample for facing bricks
Sample Density kg/m3
1 1761.03 1848.48 1777.78 1803.70 1770.37 1787.31 1868.00 1785.19 1793.48 1751.85 2 1751.80 1805.15 1748.12 1795.62 1804.51 1775.36 1791.97 1797.71 1834.59 1800.00
Batch
1 3 1794.57 1773.08 1671.33 1767.61 1792.59 1715.83 1759.69 1792.59 1812.50 1794.78 4 1776.60 1782.95 1731.06 1794.57 1775.74 1734.85 1781.48 1746.48 1802.33 1765.38 5 1785.27 1784.96 1757.64 1783.46 1780.85 1792.03 1755.47 1754.74 1721.01 1740.58 6 1781.69 1754.29 1800.75 1794.78 1752.67 1756.12 1780.14 1780.14 1779.70 1785.21 7 1705.15 1794.96 1771.74 1795.62 1778.52 1738.89 1750.35 1815.56 1747.33 1781.29 8 1847.73 1754.55 1770.21 1773.53 1760.31 1769.23 1757.86 1775.00 1759.85 1772.22 9 1782.48 1778.10 1786.86 1748.57 1789.78 1783.94 1749.29 1756.12 1789.05 1778.99
10 1773.91 1823.13 1784.44 1794.16 1771.18 1775.36 1831.58 1755.71 1774.64 1814.81
Batch 2
11 1797.81 1761.59 1778.99 1810.29 1805.88 1793.38 1820.44 1783.45 1819.12 1830.08 12 1802.17 1789.05 1822.39 1802.21 1795.59 1836.09 1774.64 1834.81 1800.73 1824.26 13 1783.94 1770.29 1784.67 1814.07 1820.90 1828.15 1807.41 1836.09 1843.28 1827.61 14 1856.72 1836.30 1805.15 1842.22 1756.83 1766.91 1813.33 1786.86 1822.06 1781.02 15 1796.27 1842.97 1764.93 1792.42 1813.85 1833.86 1771.64 1902.27 1747.76 1878.74 16 1851.16 1763.16 1763.70 1799.25 1749.62 1817.56 1784.09 1791.85 1787.97 1716.79 17 1766.92 1891.27 1775.56 1809.85 1751.82 1806.15 1762.12 1788.64 1761.65 1856.25 18 1834.38 1797.66 1767.65 1760.00 1773.33 1759.84 1840.94 1773.48 1817.32 1775.38
Batch 3
19 1733.82 1762.69 1817.69 1800.76 1754.74 1692.09 1800.00 1725.18 1739.42 1695.71 20 1784.44 1685.00 1696.40 1810.24 1793.02 1739.85 1770.00 1793.28 1755.56 1751.11 21 1768.15 1705.93 1742.96 1736.09 1716.18 1798.50 1754.55 1737.31 1790.15 1739.10 22 1829.46 1770.45 1743.61 1725.19 1760.00 1761.48 1739.10 1791.73 1747.37 1747.73 23 1821.54 1778.63 1738.35 1719.05 1765.12 1754.81 1758.02 1782.71 1738.35 1766.92 24 1783.58 1766.21 1789.84 1728.56 1792.77 1773.95 1720.93 1763.33 1788.46 1768.82 25 1767.45 1742.24 1748.89 1830.37 1803.45 1792.74 1810.54 1780.34 1811.22 1795.16 26 1756.83 1879.38 1795.56 1805.85 1741.94 1795.26 1761.12 1768.64 1759.74 1806.25
Batch 4
27 1836.83 1806.39 1805.15 1842.22 1726.54 1716.82 1797.33 1825.95 1802.17 1781.02 Descriptive Statistics Mean, x = 1781.51 kg/m3 Median = 1781.158 kg/m3 Mode = 1805.147 kg/m3 Standard deviation, s = 35.858 kg/m3 Maximum = 1902.273 kg/m3 Minimum =1671.329 kg/m3 Range, R = 230.944 kg/m3 Coefficient of variation, c.v. =2.013%
Figure 5.14 shows the histogram to represent data distribution. Assuming
that the data is normally distributed, the normal curve fit is analysed and the curve
superimposed on the histogram. From the normal curve the 33-percentile computed
from sample data shows the middle third distribution, which consists of the normal
values for density ranging from 1766 to 1795 kg/m3.
144
From Control charts for means and ranges of density (Figure 5.15), the
samples lying outside the upper and lower warning and action lines were ignored to
determine the population mean. A single factor ANOVA was carried out on the
remaining sample data to determine the components of variance in the samples
among the different batches. The variance determined from the ANOVA was 1114.0
with standard deviation of 33.38 kg/m3. The population mean neglecting the samples
outside the zones mentioned above, and with 95 % confidence limits was 1757
to1804 kg/m3. This value was higher than the average value of density i.e.1610
kg/m3 (Table 5.20) required for sound insulation purposes of the Building
Regulations of the United Kingdom.
01020304050607080
1670
.0-1
693.
1
1693
.1-1
716.
217
16.2
-173
9.3
1739
.3-1
762.
417
62.4
-178
5.5
1785
.5-1
808.
6
1808
.6-1
831.
718
31.7
-185
4.8
1854
.8-1
877.
918
77.9
-190
1.0
1901
.0-1
924.
1
Density kg/m3
Freq
uenc
y
Figure 5.14: Histogram and normal curve fit for density of
bricks
1740
1760
1780
1800
1820
0 5 10 15 20 25 30
Sample
Den
sity
kg/
m3
Mea
n
0
50
100
150
200
0 10 20 30
Sample
Den
sity
kg/
m3
Ran
ge
Figure 5.15: Control charts for mean values and ranges of samples for
density of bricks
3
3
3
3
1781.51 /35.86 /
1781.16 /mod 1805.15 /. . 2.013%
x kg ms kg mmedian kg m
e kg mc v
==
==
=
Low < 1767 kg/m3 Normal 1767 – 1795 kg/m3 High > 1795 kg/m3
145
Table 5.20: Density of bricks for sound insulation in walls and walls
with plaster finish for (Building regulations of the UK)
Wall
Plaster finish
Material
and dimensions
(mm)
Thickness
(mm)
Specified
weight at least (kg/m2) includes
finish
Number of sides
Type
Average
density of brick to be
used (kg/m3)
Solid wall Brick size mm 65 x 102.5 x 215
215
375
2
2
Lightweight
Gypsum
1610
1610
Cavity wall
255
415
2
2
Lightweight
Gypsum
1970
1970
Density of brick has been given more emphasis recently in masonry
standards. The prEN 771-1 included density as a requirement especially to identify
the acoustic property of a brick. A brick wall with thickness 102.5 mm could give a
sound reduction index of 46 dB (Curtin, et. al). Table 5.21 shows the typical sound
insulation values of masonry walls with respect to its thickness and weight.
Loudness of 40 to 50 dB is considered as faint to moderate loudness suitable for an
average home and general to private office (Drysdale, et.al).
Table 5.21: Typical sound insulation values of masonry walls
(Curtin, et. al)
Material and construction
Thickness (mm)
Weight (kg/m2)
Approximate sound
reduction index (dB)
Brick wall plastered both sides with a minimum of 12.5 mm thick plaster
215
415
49.5
Brick wall plastered both sides with a minimum of 12.5 mm thick plaster
102.5
220
46
146
5.7 Efflorescence
The results in the test for efflorescence were based on the 4 samples
(1 sample in each batch). Every brick in a sample of 10 bricks were examined for
efflorescence after the test. Based on visual examination of the exposed surfaces for
all the samples in the 4 batches no deposits of salts or any other effects of
efflorescence such as powdering or flaking could be detected.
5.8 Soluble Salt Content
Bricks were tested for the presence of acid soluble sulphates and water-
soluble salts of calcium, magnesium, potassium and sodium. Table 5.22 shows the
content of soluble salt in the samples from the various batches and the maximum
limit of salt content provided by BS 3921:1985 for the category of low salt.
Table 5.22: Percentage of soluble salts in samples from all batches Sample Calcium Sodium Potassium Magnesium Sulphate
1 0.013 0.003 0.003 0.003 0.07
Batch
1 2 0.014 0.002 0.003 0.002 0.07 3 0.003 0.004 0.006 0.002 0.09 4 0.006 0.002 0.009 0.003 0.06
Batch 2
5 0.016 0.003 0.007 0.006 0.09 6 0.010 0.001 0.003 0.004 0.02 7 0.007 0.003 0.006 0.003 0.09 8 0.011 0.002 0.005 0.004 0.04
Batch 3
9 0.007 0.001 0.003 0.003 0.02 10 0.008 0.002 0.004 0.003 0.02 11 0.009 0.002 0.004 0.003 0.02
Batch 4
12 0.010 0.002 0.004 0.005 0.02
Mean, x % 0.010 0.002 0.005 0.003 0.05 Sample standard deviation, s 0.004 0.0006 0.002 0.001 0.03
c.v. % 40.0 30.0 40.0 33.3 60.0
BS 3921:1985 0.3 % 0.03 % 0.03 % 0.03 % 0.50 %
147
The results indicated that the percentage of salts i.e. calcium, sodium,
magnesium, potassium and sulphate in the bricks were very small in comparisons
with the limits for the category of Low salt content as defined in BS 3921:1985.
The c.v. in the test for sulphate was considerably high which was about
60 %. The reason for this was most probably due to the test method used. Sulphate
was determined by the gravimetric method, which is confined to relatively high
sulphate content. The method was also considered as rather complicated and this
may contributed to the significant variability in the results (Brachtel, 2003).
The results of salt content compared with the European Standard prEN 771-1
also showed that the bricks investigated had very low salt content. The combined
content of sodium and potassium in the bricks from this research was 0.007 %,
which is very much below the maximum limits provided in prEN 771-1 for category
S1 (0.17 %) and S2 (0.06 %). Similarly, with a mean percentage of 0.003,
magnesium was also below the specified maximum limit i.e. 0.08 and 0.03 for
category S1 and S2 respectively. Thus the bricks fit into the category of application
of S1 and S2 as defined in the European Standard; S1 is for normal exposure and S2
is suitable for prolonged saturation applications.
CHAPTER 6
APPLICATIONS OF RESEARCH FINDINGS
6.1 Relationship of Aspect Ratio to Compressive Strength
In masonry construction bricks are normally laid on the bed face, which yield
the greatest compressive strength compared to if laid in the stretcher or header faces.
A relationship between the compressive strengths of units and their aspect ratio (h/t),
was proposed through the research findings described in the earlier chapters. The
compressive strengths are related to h/t as described by the following relationship:
16.35 58.17f x= − + …(6.1)
Where,
f = compressive strengths of a brick (N/mm2)
x =aspect ratio (height to thickness ratio, h/t).
The above relationship was obtained by the best-fit line with a regression
coefficient of R2 = 0.998 (Figure 6.1)
149
f = -16.353x + 58.168R2 = 0.998
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5 3 3.5
Height to thickness ratio, h/tC
ompr
essi
ve st
reng
th, f
N/m
m2
Figure 6.1: Relationship between compressive strength
and h/t ratio of bricks.
Equation 6.1 can be used to estimate compressive strength of a brick for
various h/t ratio greater than 0.7 but less than 3.2. The dimensions h and t are
defined accordingly to the orientation of bricks in a brick laying (Figure 6.2), where
h = height of the brick normal to the loading axis,
t = smaller dimension of the loaded surface area.
W= direction of loading on wallW
WW
(c)
t
h
(b)(a) t
hh
t
(b) bed face (c) stretcher face
Figure 6.2: Orientation of bricks in a brick laying (a) header face
150
The estimated strength provides useful information to manufacturers as well
as designers in assessing the compressive strength of a brick when loaded in the
various orientations without conducting any tests, as yet giving an important data for
use in preliminary design or strength assessment. The proposed relationship is also
convenient to users where facilities for testing are not available at hand. The
applicability of the proposed estimated relationship is only valid under the following
conditions:
• The bricks are fired clay bricks.
• Percentage of perforations is about 20 %
• The aspect ratio h/t must lie between 0.7 to 3.2
It should be noted that the estimated compressive strengths for bricks loaded
on the bed face as derived in equation 6.1 is based on gross loaded area whereby
perforated areas were ignored. This tends to yield a smaller compressive strength
than if computed using net area. Hence, the prediction given by this formula for
perforated bricks tested on bed face is conservative.
Conventionally the compressive strength test provides the strength of bricks
when loaded on bed face. The relationship between the compressive strength of
bricks when loaded on the bed face and in other test orientations are considered
important for design and preliminary assessment purposes.
An attempt is made to establish this relationship, based on the research
findings described in previous chapters and illustrated below. The compressive
strength of bricks when loaded on the bed face is used as a standard measure as it is
the only available data in any compressive test.
Assuming fb, fs and fh are the corresponding compressive strength of bricks
in the bed, stretcher and header faces. Substituting the values of fb and fs as 46.1 and
34.7 N/mm2 for compressive strengths of bricks in this research, therefore a ratio of
fs : fb can be established as shown in equation 6.2.
151
34.7 0.7546.1
s
b
ff
= = …(6.2)
or,
0.75s bf f= …(6.3)
Similarly, the compressive strength due to loading on the header face (fh=
5.5 N/mm2) can be derived in terms of fb as shown in equation 6.4.
5.5 0.1246.1
h
b
ff
= = …(6.4)
fh = 0.12 fb …(6.5)
For fired clay bricks the ratio of compressive strength for bricks tested on the
stretcher face to bed face, 0.75s
b
ff
= . The ratio of compressive strength for bricks
tested on the header face to the bed face, 0.12h
b
ff
= .
This is a convenient method of projecting the test results to other orientations
in the absence of laboratory facilities, and also acts as a guide to some preliminary
design work. It is to be noted, however, that the relationship of equation 6.3 and 6.5,
are valid provided that the conditions stated earlier are satisfied.
6.2 Relationship of Water Absorption to Porosity and Compressive Strength
Recent investigation on brick porosity and water absorption (Khalaf, 2002)
has indicated that there is a relationship between water absorption, porosity and
compressive strength. Table 6.1 shows the results of bricks compressive strength,
water absorption and porosity obtained by Khalaf.
152
Table 6.1: Relationship between bricks compressive strength, water
absorption and porosity (Khalaf, 2002)
Brick Type
Full-brick compressive
strength (N/mm2)
Water absorption of brick units BS 3921
(5-hr boil) (%)
Porosity of brick lumps by
vacuum (%)
Class B engineering 92 6.0 14.85 Clay 10 hole 81 6.2 16.75 Clay 3 slot and 8 hole 68 5.8 17.39 Clay frogged common 39 12.9 25.04 Granite - 2.63 6.15
Using the results from Table 6.1 the graphs as shown in Figure 6.3 and 6.4
were plotted to show the relationship of water absorption to porosity and
compressive strength of bricks respectively.
y = 0.74x - 6.05R2 = 0.9348
468
101214
14 16 18 20 22 24 26
Porosity (%)
Wat
er a
bsor
ptio
n,%
( 5
-hr
boili
ng)
Figure 6.3: Relationship of water absorption with porosity
from Table 6.1
f = -4.97x + 161.96R2 = 0.9497
020406080
100
14 16 18 20 22 24 26
Porosity (%)
Full-
bric
k co
mpr
essi
vest
reng
th, f
(N/m
m2 )
Figure 6.4: Relationship of porosity with compressive strength
from Table 6.1
The relationship of water absorption with porosity (Figure 6.3) was used to
determine the porosity of the bricks in this investigation as shown in equation 6.6
153
0.74 6.05y x= − …(6.6)
Where,
y = water absorption (%)
x = porosity (%)
Substituting y = 11.2% i.e. the mean water absorption for the bricks in this
investigation, in equation 6.6, the porosity, x = 23 %
The relationship of porosity with compressive strength is shown in Figure
6.4. Knowing the porosity the compressive strength could be derived from the
relationship as described by equation 6.7
4.97 161.96f x= − + …(6.7)
Where,
f = compressive strength (N/mm2)
x = porosity ( %)
Substituting the porosity, x = 23 % in equation 6.7, the compressive strength
computed was 47.65 N/mm2, which was close to the value of the mean compressive
strength in this research i.e. 46.1 N/mm2. Thus it could be assumed that the bricks in
this investigation had a porosity of about 23 %. However it is to be noted that the
porosity derived in this equation was based on results of 20 mm bricks lumps.
CHAPTER 7
CONCLUSIONS AND RECOMMENDATIONS
FOR FURTHER WORK
7.1 Conclusions
The conclusions are divided into two sections i.e. the general conclusions
and the detailed conclusions. The general conclusions dealt with properties found in
the present Malaysian standards (MS 76 Part 2:1972) i.e. compressive strengths,
water absorption, dimensional tolerance and soluble salt content. The detailed
conclusions consist of other aspects of the properties evaluation arising from
comparisons conducted with other international standards and the varying test
methods and measurements used by these standards. The section also contains new
properties consisting of initial rate of suction and density useful for the development
of masonry standards.
7.2 General Conclusions
The mean compressive strength of facing bricks falls in the range of
40 N/mm2 to 50 N/mm2 and common bricks 30 N/mm2 to 40 N/mm2. The bricks fall
within the higher range of compressive strengths specified in Malaysian Standard
MS 76:1972 and therefore regarded as load bearing units.
155
The mean water absorption of the bricks investigated was 10 % to 12 %,
which lied outside the specified limits for Engineering A (≤4.5 %) and Engineering
B (≤7 %) of the Malaysian/British Standard.
The results on the overall dimensions of 24 bricks showed that both the
length and the width fall within the permissible tolerance of the Malaysian
Standard/British Standard. However, the height exceeded the Malaysian Standard/
British Standard tolerance limit considerably by about 37 mm. Therefore, the
category of dimensional deviations in existing Malaysian standard, which was based
on the BS overall measurement of 24 bricks need to be modified accordingly.
The content of calcium, magnesium, potassium, sodium and sulphate in the
bricks was very negligible and thus they fall under the durability designation of
“Low” (L) of soluble salt content as per BS 3921:1985. In accordance to European
Standard, the bricks could be applied even for the worst condition of construction
application i.e. S2, which is meant for masonry structures subjected to prolonged
wet situation.
7.3 Detailed Conclusions
7.3.1 Compressive strengths
The range of mean compressive strength obtained in the bricks surpass the
minimum value i.e. 20.7 N/mm2 specified for compressive strength of facing brick
in ASTM C216-90a to be used in SW (severe weathering) regions. Under Singapore
Standard SS 103:1974, the bricks could be categorised as the First Grade bricks.
Considerable reduction of compressive strength was observed when bricks
were tested in the different orientations. When tested on the stretcher face the
compressive strength was approximately 60 % to 90 % of the compressive strength
tested on bed face. On the header face the compressive strength was further reduced
156
to about 10 % to 15 % of the strength tested on bed face. Hence, compressive
strength should be indicated with the brick orientation for testing.
Compressive strength of bricks is affected by curing conditions before
testing. Dry bricks show higher compressive strengths than wet bricks. The
compressive strength of bricks evaluated in the tests was based on saturated
condition, therefore, providing conservative values by about 15 to 20 %.
Additionally, the compressive strength was computed based on gross area, further
reducing the compressive strength by approximately 20 %.
7.3.2 Water Absorption
Although the bricks researched could not satisfy the requirements for the
water absorption in the Malaysian Standard (MS 76:1972), the values were well
within the requirements provided in ASTM for Grade SW and MW bricks with
water absorption limits of 17 % and 22 % respectively.
Malaysian bricks tend to have high water absorption, typically greater than
10 %, and this can be explained by the limestone content in the soil. This is not a
characteristic of British soil, therefore water absorption in British bricks are usually
lower.
The water absorption of the bricks investigated corresponds to the second
level of the characteristic flexural strength of BS 5628: Part 1, denoted by strengths
of 0.35 to 1.5 N/mm2, which depend on the mortar designation and the plane of
failure. These values are required in the design of masonry structures.
The relation of water absorption to porosity showed that the porosity of the
bricks in this investigation was about 23 %. Compressive strength of bricks could be
related to their porosity and this relationship would be useful for a preliminary
estimation of compressive strength.
157
7.3.3 Dimensional Tolerance
Comparison of results with the recent European Standard shows that the
bricks investigated satisfy the category of T1 of prEN 771-1.
7.3.4 Initial Rate of Suction
The bricks in this investigation had a mean initial rate of suction of 1.4 to 2.0
kg/m2.min, which fall under the high range of IRS. Ideally, the value of IRS should
be between 0.25 to 1.5 kg/min.m2 for the development of appropriate bond strength
between the bricks and the mortar interface. ASTM recommends that bricks with
IRS exceeding 1.5 kg/min.m2 should be wetted before laying. The bricks indicted
high values of IRS hence requiring pre-wetted surface before laying in order to
optimise bonding upon laying on to mortar. This is considered more critical in hot
weather construction since hot bricks will absorb more water and the water in mortar
will be depreciated at a faster rate with high temperature.
The range of IRS values of 1.4 to 2.0 kg/m2.min demonstrated by the bricks
in this investigation was determined using gross area i.e. without reducing the area
of immersion by the area of perforations. The IRS calculated using net area of
immersion shows an IRS value higher than about 18 % if based on gross area. The
BS 3921:1985 computed the IRS based on gross area while the ASTM and AS/NZS
use the net area. It is therefore significant that IRS values be clearly indicated for
both cases of calculation to avoid confusion. Therefore, specification for IRS values
should be denoted as IRSgross or IRSnet depending on the surface area of immersion.
158
7.3.5 Soluble Salt Content
The soluble salt content for all the minerals under investigations i.e. calcium,
sodium, potassium, magnesium and sulphate were all below the maximum limits
specified in the British Standard. This justifies the reason why salt does not appear
on the brick surfaces in the efflorescence test. The effects of sulphate have been
given a considerable attention in existing standards, however this is not the case for
EN 771-1. The European standard considered the sulphate action a complex matter
to be dealt with in the national design codes. Sodium and potassium has been
analysed as a combined effect in the EN, with maximum values of 0.17 %
depending on the application category. In this case the research results of 0.007 %
does not exceed the recommended percentage of the EN. The percentage of sulphate
present in the bricks was 0.05 %. This value is much below the maximum of 0.5 %
allowed for in the BS 3921.
7.3.6 Density
The density of the bricks in this investigation is within the range of 1757
kg/m3 to 1804 kg/m3. Previous works imply that the bricks in this range use in a
102.5 mm thick wall could give a sound insulation of 40 to 50 dB (Curtin et al.,
1995) which is considered as faint to moderate loudness suitable for an average
home and general to private office (Drysdale et al., 1994). The density of the bricks,
also suffice the requirements for sound insulation specified in the building
regulations in the United Kingdom.
7.4 Recommendations for Further Work
The bricks properties reported herein was based on a production from a
single manufacturer of clay bricks. Future studies should include other
manufacturers of clay bricks in order to achieve results representative of the entire
159
population of bricks in the country. The results representing the whole population
would characterise local production and therefore useful in the development of
national standards. Recommendations for future research should include the
following:
(i) Sampling should be obtained from a larger number of manufacturers
across the country for a more representative estimate of the properties and to
include various types of bricks in local production.
(ii) In order to get a more comprehensive relationship of the compressive
strengths with the bricks aspect ratio (h/t), bricks samples should comprise
other formats and configurations to include a wider range of bricks types.
In this research, bricks were generally tested in accordance to the British
standard procedure. However, procedures from other standards were also looked
into and regarded as more reliable and accurate. Some recommendations to be
considered in the testing methods for future studies include:
(i) Investigation on the density of bricks should be determined for both
the dry and ambient condition.
(ii) Evaluation of water absorption by the 5-hr boiling test involving the
use of small brick lumps as specimen instead of the normal whole brick may
be considered. This new method would certainly be more economical
because less fuel would be needed in boiling the small specimen. Moreover,
the handling of experiments would be more convenient with small specimens
especially in testing that implicate a large amount of samples as experienced
in this research. Further, it was claimed that this new method could produce
results that are more accurate.
(iii) In the preparation of specimens for the tests of water absorption and
IRS, BS 3921 procedure for attaining constant mass when drying bricks in
the oven is by heating the bricks for at least 48 hrs. The ASTM and
Australian standard monitor the change of mass at specified intervals. Bricks,
160
which are recently manufactured, normally have very small moisture content.
Thus, they may not need too long a duration for example the 48 hours
assumed to attain constant mass. Therefore, by monitoring the weight loss
may reduce the time of heating and consequently economise on the use of
energy. For this matter, it is recommended that the AS/NZS 4456 or the
ASTM C 67 be adopted in the laboratory procedure for attaining constant
mass of bricks.
(iv) In the test for IRS, standard method should incorporate ways of
ensuring a consistent 3 mm immersion during the test. This could be helpful
in attaining more precise results.
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Grimm, C.T. (1975). “Strength and related properties of brick masonry.” Journal of
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Design, Construction, and Maintenance, pp. 169-192.
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building Materials, 15. 323-330. Elsevier.
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Toronto, Sydney, Braunschweig.: Pergamon Press,
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Morton, J. (1986). “The design of laterally loaded walls.” TGV Publications.
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Segmental pavers- Methods of test.” (AS/NZS 4456.0- 4456.18:1997)
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Fired Brickearth, Clay Or Shale.” (MS 76 Part 2).
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Indices For Clay Bricks.” Journal Of Architectural Engineering.
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Hall.
APPENDICES
A 1
RESULTS OF TESTS SPECIMENS
FOR DIMENSIONAL TOLERANCE OF
INDIVIDUAL BRICKS
167 Table A1-1: Individual measurement for length
Sample Length 1 218.00 218.60 217.55 218.50 218.85 219.10 2 218.45 220.20 217.70 218.35 218.30 217.60 3 217.05 219.45 216.90 213.30 215.15 217.65 4 218.60 219.55 216.90 217.90 218.20 217.00 5 216.20 217.20 217.45 215.95 216.35 216.25 6 219.10 217.90 217.45 218.30 217.00 216.30 7 217.40 216.90 216.60 218.75 217.00 219.40
Batch 1
8 220.60 217.40 219.85 218.30 220.35 217.95 9 215.75 218.00 217.85 216.50 217.85 213.90 10 214.50 220.45 214.25 218.40 215.60 210.00 11 217.10 214.50 217.20 216.10 217.85 214.00 12 213.55 217.25 219.35 218.30 214.75 214.90 13 217.20 220.65 219.00 215.30 221.20 214.70 14 217.70 216.10 216.30 219.80 216.50 219.60 15 219.45 217.80 220.55 217.00 214.40 216.85 16 221.30 217.25 218.00 219.25 216.80 220.30 17 217.00 215.75 215.95 217.35 217.20 217.40 18 218.35 217.70 220.25 218.50 219.50 219.50 19 217.80 218.30 214.35 217.95 217.00 214.55 20 217.25 217.00 217.25 217.30 220.65 217.00 21 220.00 220.70 216.00 217.70 220.55 219.35 22 218.25 218.50 214.15 221.15 214.80 218.10 23 214.95 214.95 214.35 219.25 216.50 217.75
Batch 2
24 218.25 209.75 220.30 220.75 220.00 218.75 25 217.00 214.90 215.10 217.00 215.20 215.25 26 215.00 214.70 213.40 213.50 215.25 215.85 27 214.75 215.50 214.25 215.85 216.20 214.00 28 215.00 215.60 212.70 214.70 216.00 214.00 29 215.60 214.65 216.90 215.35 214.85 215.25 30 215.00 216.25 217.00 215.75 217.25 216.30 31 215.30 214.00 215.00 216.80 214.25 212.90 32 215.20 215.00 215.65 215.25 217.15 216.00 33 215.75 216.30 213.30 215.45 214.00 216.35 34 216.90 214.15 214.70 216.95 215.35 214.65 35 215.25 215.55 216.00 215.45 214.25 214.25 36 215.00 215.00 213.85 215.75 216.00 215.00 37 215.50 216.55 217.30 216.00 216.00 215.00 38 215.15 215.00 215.25 215.00 214.00 215.45 39 215.40 214.25 215.00 214.65 214.00 215.30
Batch 3
40 216.10 214.35 214.45 215.25 214.40 216.50 41 216.60 216.60 215.70 216.35 217.25 216.00 42 215.50 216.85 218.00 214.65 215.45 216.95 43 214.75 214.85 216.20 215.00 215.6 217.40 44 216.20 213.55 214.75 216.10 213.25 216.70 45 213.75 215.10 214.05 215.70 217.25 214.70 46 216.50 217.25 215.75 214.00 215.40 215.25 47 216.50 215.00 215.75 217.75 214.00 215.30 48 218.50 217.75 216.00 213.65 216.40 214.75 49 215.55 214.60 215.15 215.65 220.30 220.25 50 215.95 212.75 215.10 214.10 214.00 215.50 51 214.25 216.60 215.75 220.40 216.8 217.25 52 220.95 216.00 216.60 216.00 214.10 218.35 53 215.95 216.75 216.70 212.75 216.00 216.85 54 215.45 215.45 216.00 214.40 215.00 215.85 55 216.25 215.25 216.40 215.55 216.10 217.30
Batch 4
56 216.95 215.50 216.00 216.25 216.00 216.95
168 Table A1-2: Individual measurement for width
Sample Width 1 100.75 100.2 100.3 98.8 101.2 100.1 2 99.85 101 99.3 100.4 99.1 99.1 3 99.2 99.85 99.35 97.7 98 99.9 4 99.8 100.1 99.8 99.65 99.05 99.4 5 99.3 98 100.5 98.25 99.4 98.3 6 100.1 100.7 99.35 100.75 99 99 7 99.35 100 99.9 99.9 99.45 101.2
Batch 1
8 101.1 99.55 99.7 98.85 100.6 99.65 9 98.20 102.50 100.75 100.00 100.00 98.15 10 98.30 101.80 97.70 99.80 99.25 99.00 11 100.05 98.35 100.35 99.75 99.50 98.00 12 97.60 100.00 101.15 100.00 98.00 96.35 13 99.65 102.15 101.35 100.00 101.45 97.85 14 101.75 99.00 99.65 101.25 99.15 100.80 15 100.95 100.50 101.35 99.60 97.65 98.95 16 102.65 99.55 98.80 101.10 100.10 102.20 17 100.65 98.65 99.85 100.85 98.95 99.65 18 101.10 100.85 101.30 100.75 100.10 101.25 19 100.50 100.90 98.65 100.00 99.25 99.25 20 100.00 99.00 99.95 100.25 101.60 100.50 21 102.00 102.30 98.40 100.00 102.75 100.75 22 101.00 100.50 98.45 102.70 96.80 99.40 23 98.75 98.00 98.00 101.25 99.50 100.95
Batch 2
24 98.75 98.80 99.25 99.55 102.95 100.50 25 100.75 98.50 99.40 100.60 99.10 100.05 26 100.10 98.85 98.80 99.10 99.80 100.50 27 99.90 100.55 99.30 100.75 100.75 97.60 28 100.00 100.75 99.25 99.55 100.75 99.10 29 99.20 99.25 100.90 100.25 98.75 99.65 30 99.55 100.55 100.20 100.30 101.35 100.75 31 97.60 99.15 100.00 100.85 99.90 98.80 32 99.85 99.50 100.45 99.75 101.55 100.50 33 99.65 100.45 98.50 100.50 98.25 99.00 34 100.35 100.25 99.75 100.10 99.50 100.00 35 100.00 98.80 100.30 98.25 99.50 97.30 36 99.25 99.00 98.55 98.75 98.65 98.00 37 100.25 100.50 101.30 98.30 99.45 99.10 38 99.50 99.65 99.25 99.65 99.00 98.25 39 100.50 99.25 99.15 99.15 99.25 100.25
Batch 3
40 100.35 100.25 99.75 99.55 100.15 100.95 41 101.10 100.00 99.80 99.30 100.60 100.60 42 100.10 100.55 100.30 97.75 100.25 99.70 43 98.95 98.00 100.95 98.70 100.45 100.75 44 99.25 97.50 97.00 100.20 98.15 101.25 45 98.35 98.30 97.45 99.30 100.75 98.20 46 100.25 100.30 99.70 97.15 99.25 99.90 47 99.75 99.75 99.25 100.25 98.00 97.75 48 100.00 100.25 98.50 97.50 100.65 98.00 49 99.55 99.20 98.45 98.85 102.50 102.85 50 99.20 98.75 99.65 98.00 99.60 98.85 51 98.80 99.95 99.25 102.00 99.95 100.20 52 100.75 99.30 99.65 99.60 98.60 100.50 53 99.85 100.25 99.25 100.15 99.90 100.35 54 99.70 101.00 99.50 99.70 97.95 99.00 55 100.75 99.55 100.25 100.30 100.50 100.25
Batch 4
56 99.70 100.00 100.50 99.10 100.25 99.25
169
Table A1-3: Individual measurement for height.
Sample Height 1 67.10 67.10 67.75 66.60 66.70 67.25 2 66.75 67.80 67.80 67.90 66.30 66.85 3 69.05 67.20 67.40 66.75 66.50 67.80 4 69.40 67.00 63.95 66.10 69.25 67.45 5 66.20 66.40 65.90 66.60 66.10 67.00 6 67.50 66.75 67.45 67.65 67.00 66.60 7 67.50 67.30 68.20 68.25 68.30 67.90
Batch 1
8 67.50 67.30 69.30 67.75 68.75 67.45 9 67.85 67.65 71.00 67.80 68.00 66.75 10 67.20 68.50 68.00 69.20 68.25 65.80 11 68.10 67.00 68.30 67.50 69.45 68.00 12 67.35 67.65 69.10 67.40 67.90 66.60 13 67.20 68.05 68.25 68.35 68.00 69.20 14 67.95 66.20 66.35 67.95 66.95 68.10 15 68.50 67.75 68.45 66.85 67.60 66.85 16 68.70 66.75 71.00 69.25 69.15 68.00 17 67.00 68.55 67.55 67.50 66.95 68.05 18 68.95 67.25 68.80 67.50 67.85 69.10 19 69.25 67.05 68.00 68.75 68.00 68.00 20 68.75 67.90 68.75 67.75 68.25 67.20 21 68.65 69.10 66.00 68.15 68.55 68.05 22 69.90 69.25 67.95 68.55 66.50 69.25 23 66.75 68.25 68.75 67.75 68.15 67.50
Batch 2
24 68.25 66.10 67.75 68.00 68.75 68.50 25 67.65 67.20 67.00 67.50 67.15 66.60 26 67.15 67.25 66.65 66.25 67.00 67.25 27 67.00 67.20 66.85 67.50 68.00 66.00 28 67.00 67.25 66.50 67.00 67.50 67.25 29 67.15 67.20 67.75 67.45 67.70 67.30 30 67.55 67.95 68.00 67.95 67.25 67.30 31 66.75 66.00 68.30 67.90 68.55 66.70 32 67.25 67.25 67.75 67.00 68.50 67.50 33 67.65 67.50 66.00 67.25 66.85 68.85 34 67.80 67.00 67.75 67.35 66.25 67.20 35 67.20 67.00 67.00 67.00 66.85 67.00 36 66.75 66.25 68.00 67.00 67.25 67.05 37 67.00 67.35 67.60 66.75 67.00 66.55 38 66.60 67.45 66.55 67.15 66.75 66.50 39 66.75 67.00 66.75 66.95 67.00 67.30
Batch 3
40 67.75 67.00 66.50 67.25 66.75 67.25 41 67.30 68.00 67.55 68.35 68.00 67.00 42 67.70 67.55 68.00 66.60 67.50 67.80 43 67.45 67.15 67.50 66.80 68.00 67.55 44 67.60 66.35 66.50 68.25 66.70 67.35 45 66.80 67.50 66.85 67.20 68.50 66.85 46 67.80 67.80 67.90 66.35 67.75 67.00 47 67.80 65.95 67.65 65.00 66.30 66.75 48 69.25 68.25 67.75 66.35 67.50 66.35 49 66.70 66.90 67.00 67.00 68.25 68.25 50 68.25 66.10 67.10 66.85 66.70 67.20 51 66.30 67.00 67.90 68.20 67.60 68.15 52 68.55 67.35 65.25 66.75 67.10 67.05 53 67.75 68.95 69.25 68.80 67.20 67.75 54 67.00 67.35 67.70 67.25 66.60 67.25 55 67.25 67.00 67.75 67.25 66.85 68.50
Batch 4
56 67.25 67.25 67.20 67.80 67.75 67.50
A 2
RESULTS OF TEST SPECIMENS
FOR DENSITY OF BRICKS
171
Brick Weight (mo) Weight after Immersed Volume (V) Density (Da) identification as received 2 hrs soaking (m1) weight (m2) V=(m1-m2)*1000 mo/V*1,000,000
(gm) (gm.) (gm) mm3 kg/m3 51 2295 2630 1270 1360000 1687.50 27 2450 2590 1270 1320000 1856.06 48 2475 2620 1270 1350000 1833.33 67 2351 2650 1300 1350000 1741.48 32 2545 2630 1280 1350000 1885.19 6 2410 2600 1260 1340000 1798.51
19 2435 2470 1220 1250000 1948.00 22 2415 2610 1260 1350000 1788.89 50 2477 2690 1310 1380000 1794.93
Sam
ple
1
9 2545 2600 1250 1350000 1885.19 36 2435 2690 1300 1390000 1751.80 44 2455 2640 1280 1360000 1805.15 43 2325 2570 1240 1330000 1748.12 64 2460 2670 1300 1370000 1795.62 38 2400 2600 1270 1330000 1804.51 45 2450 2680 1300 1380000 1775.36 62 2455 2670 1300 1370000 1791.97 30 2355 2560 1250 1310000 1797.71 70 2440 2620 1290 1330000 1834.59
Sam
ple
2
66 2430 2630 1280 1350000 1800.00 85 2315 2520 1230 1290000 1794.57 92 2305 2530 1230 1300000 1773.08 41 2390 2680 1250 1430000 1671.33 96 2510 2770 1350 1420000 1767.61 87 2420 2650 1300 1350000 1792.59 43 2385 2680 1290 1390000 1715.83 91 2270 2490 1200 1290000 1759.69 42 2420 2640 1290 1350000 1792.59 81 2465 2690 1330 1360000 1812.50
Sam
ple
3
99 2405 2650 1310 1340000 1794.78 82 2505 2760 1350 1410000 1776.60 88 2300 2510 1220 1290000 1782.95 95 2285 2540 1220 1320000 1731.06 84 2315 2530 1240 1290000 1794.57 98 2415 2650 1290 1360000 1775.74 86 2290 2540 1220 1320000 1734.85 100 2405 2640 1290 1350000 1781.48 97 2480 2740 1320 1420000 1746.48 90 2325 2530 1240 1290000 1802.33
Sam
ple
4
89 2295 2560 1260 1300000 1765.38 2 2303 2510 1220 1290000 1785.27
52 2374 2600 1270 1330000 1784.96 3 2531 2790 1350 1440000 1757.64 1 2372 2630 1300 1330000 1783.46 9 2511 2740 1330 1410000 1780.85
14 2473 2690 1310 1380000 1792.03 6 2405 2630 1260 1370000 1755.47
50 2404 2610 1240 1370000 1754.74 10 2375 2600 1220 1380000 1721.01
Sam
ple
5
7 2402 2660 1280 1380000 1740.58 46 2530 2750 1330 1420000 1781.69 49 2456 2710 1310 1400000 1754.29 55 2395 2600 1270 1330000 1800.75 4 2405 2630 1290 1340000 1794.78
56 2296 2520 1210 1310000 1752.67 57 2441 2700 1310 1390000 1756.12 12 2510 2740 1330 1410000 1780.14 48 2510 2740 1330 1410000 1780.14 54 2367 2620 1290 1330000 1779.70
Sam
ple
6
5 2535 2760 1340 1420000 1785.21 26 2319 2560 1200 1360000 1705.15 69 2495 2720 1330 1390000 1794.96 33 2445 2700 1320 1380000 1771.74 30 2460 2710 1340 1370000 1795.62 35 2401 2630 1280 1350000 1778.52 29 2504 2780 1340 1440000 1738.89 31 2503 2770 1340 1430000 1750.35 59 2451 2660 1310 1350000 1815.56 37 2289 2520 1210 1310000 1747.33
Sam
ple
7
22 2476 2710 1320 1390000 1781.29
172
66 2439 2610 1290 1320000 1847.73 28 2509 2780 1350 1430000 1754.55 34 2496 2740 1330 1410000 1770.21 21 2412 2630 1270 1360000 1773.53 67 2306 2540 1230 1310000 1760.31 32 2530 2780 1350 1430000 1769.23 58 2461 2700 1300 1400000 1757.86 45 2343 2570 1250 1320000 1775.00 68 2411 2660 1290 1370000 1759.85
Sa
mpl
e 8
94 2233 2450 1190 1260000 1772.22 16 2442 2660 1290 1370000 1782.48 10 2436 2650 1280 1370000 1778.10 14 2448 2650 1280 1370000 1786.86 20 2448 2700 1300 1400000 1748.57 21 2452 2670 1300 1370000 1789.78 11 2444 2650 1280 1370000 1783.94 24 2449 2700 1300 1400000 1749.29 18 2441 2660 1270 1390000 1756.12 7 2451 2660 1290 1370000 1789.05
Sam
ple
9
23 2455 2670 1290 1380000 1778.99 15 2448 2660 1280 1380000 1773.91 22 2443 2630 1290 1340000 1823.13 19 2409 2600 1250 1350000 1784.44 17 2458 2660 1290 1370000 1794.16 13 2446 2670 1289 1381000 1771.18 9 2450 2670 1290 1380000 1775.36 8 2436 2600 1270 1330000 1831.58 5 2458 2700 1300 1400000 1755.71
12 2449 2680 1300 1380000 1774.64
Sam
ple
10
3 2450 2650 1300 1350000 1814.81 83 2463 2660 1290 1370000 1797.81 82 2431 2660 1280 1380000 1761.59 79 2455 2680 1300 1380000 1778.99 86 2462 2650 1290 1360000 1810.29 72 2456 2640 1280 1360000 1805.88 88 2439 2630 1270 1360000 1793.38 77 2494 2670 1300 1370000 1820.44 91 2479 2700 1310 1390000 1783.45 94 2474 2650 1290 1360000 1819.12
Sam
ple
11
89 2434 2600 1270 1330000 1830.08 92 2487 2690 1310 1380000 1802.17 84 2451 2650 1280 1370000 1789.05 81 2442 2620 1280 1340000 1822.39 93 2451 2640 1280 1360000 1802.21 90 2442 2640 1280 1360000 1795.59 75 2442 2610 1280 1330000 1836.09 80 2449 2670 1290 1380000 1774.64 95 2477 2650 1300 1350000 1834.81 96 2467 2660 1290 1370000 1800.73
Sam
ple
12
76 2481 2640 1280 1360000 1824.26 50 2444 2680 1310 1370000 1783.94 68 2443 2690 1310 1380000 1770.29 73 2445 2680 1310 1370000 1784.67 53 2449 2660 1310 1350000 1814.07 64 2440 2640 1300 1340000 1820.90 49 2468 2680 1330 1350000 1828.15 52 2440 2660 1310 1350000 1807.41 54 2442 2640 1310 1330000 1836.09 55 2470 2660 1320 1340000 1843.28
Sam
ple
13
61 2449 2630 1290 1340000 1827.61 74 2488 2700 1360 1340000 1856.72 56 2479 2710 1360 1350000 1836.30 57 2455 2680 1320 1360000 1805.15 60 2487 2670 1320 1350000 1842.22 71 2442 2700 1310 1390000 1756.83 51 2456 2710 1320 1390000 1766.91 65 2448 2630 1280 1350000 1813.33 66 2448 2690 1320 1370000 1786.86 58 2478 2710 1350 1360000 1822.06
Sam
ple
14
59 2440 2670 1300 1370000 1781.02
173
14 2407 2620 1280 1340000 1796.27 19 2359 2520 1240 1280000 1842.97 1 2365 2610 1270 1340000 1764.93
24 2366 2580 1260 1320000 1792.42 18 2358 2540 1240 1300000 1813.85 17 2329 2470 1200 1270000 1833.86 13 2374 2600 1260 1340000 1771.64 15 2511 2640 1320 1320000 1902.27 20 2342 2600 1260 1340000 1747.76
Sam
ple
15
16 2386 2510 1240 1270000 1878.74 22 2388 2550 1260 1290000 1851.16 11 2345 2590 1260 1330000 1763.16 6 2381 2600 1250 1350000 1763.70 5 2393 2600 1270 1330000 1799.25 4 2327 2580 1250 1330000 1749.62 3 2381 2590 1280 1310000 1817.56 9 2355 2560 1240 1320000 1784.09 2 2419 2650 1300 1350000 1791.85 7 2378 2600 1270 1330000 1787.97
Sam
ple
16
8 2352 2640 1270 1370000 1716.79 31 2350 2600 1270 1330000 1766.92 47 2383 2510 1250 1260000 1891.27 44 2397 2660 1310 1350000 1775.56 35 2389 2570 1250 1320000 1809.85 36 2400 2620 1250 1370000 1751.82 45 2348 2550 1250 1300000 1806.15 39 2326 2580 1260 1320000 1762.12 40 2361 2580 1260 1320000 1788.64 29 2343 2590 1260 1330000 1761.65
Sam
ple
17
32 2376 2520 1240 1280000 1856.25 46 2348 2520 1240 1280000 1834.38 37 2301 2510 1230 1280000 1797.66 40b 2404 2630 1270 1360000 1767.65 26 2376 2630 1280 1350000 1760.00 41 2394 2640 1290 1350000 1773.33 30 2235 2470 1200 1270000 1759.84 38 2338 2490 1220 1270000 1840.94 27 2341 2570 1250 1320000 1773.48 25 2308 2490 1220 1270000 1817.32
Sam
ple
18
28 2308 2540 1240 1300000 1775.38 54 2358 2590 1230 1360000 1733.82 56 2362 2570 1230 1340000 1762.69 53 2363 2520 1220 1300000 1817.69 50 2359 2530 1220 1310000 1800.76 68 2404 2630 1260 1370000 1754.74 67 2352 2640 1250 1390000 1692.09 52 2322 2510 1220 1290000 1800.00 57 2398 2650 1260 1390000 1725.18 58 2383 2620 1250 1370000 1739.42
Sam
ple
19
61 2374 2670 1270 1400000 1695.71 64 2409 2620 1270 1350000 1784.44 62 2359 2670 1270 1400000 1685.00 70 2358 2660 1270 1390000 1696.40 55 2299 2450 1180 1270000 1810.24 65 2313 2500 1210 1290000 1793.02 59 2314 2530 1200 1330000 1739.85 63 2301 2520 1220 1300000 1770.00 66 2403 2590 1250 1340000 1793.28 69 2370 2590 1240 1350000 1755.56
Sam
ple
20
71 2364 2590 1240 1350000 1751.11 74 2387 2620 1270 1350000 1768.15 84 2303 2550 1200 1350000 1705.93 82 2353 2600 1250 1350000 1742.96 76 2309 2560 1230 1330000 1736.09 85 2334 2560 1200 1360000 1716.18 96 2392 2590 1260 1330000 1798.50 94 2316 2550 1230 1320000 1754.55 91 2328 2580 1240 1340000 1737.31 79 2363 2580 1260 1320000 1790.15
Sam
ple
21
78 2313 2560 1230 1330000 1739.10
174
90 2360 2510 1220 1290000 1829.46 73 2337 2550 1230 1320000 1770.45 93 2319 2560 1230 1330000 1743.61 89 2329 2590 1240 1350000 1725.19 77 2288 2500 1200 1300000 1760.00 80 2378 2620 1270 1350000 1761.48 88 2313 2560 1230 1330000 1739.10 79 2383 2580 1250 1330000 1791.73 81 2324 2560 1230 1330000 1747.37
Sam
ple
22
86 2307 2540 1220 1320000 1747.73 61 2368 2510 1210 1300000 1821.54 60 2330 2530 1220 1310000 1778.63 58 2312 2550 1220 1330000 1738.35 57 2319 2590 1240 1350000 1717.78 56 2277 2500 1210 1290000 1765.12 54 2369 2610 1260 1350000 1754.81 53 2303 2540 1230 1310000 1758.02 52 2371 2570 1240 1330000 1782.71 51 2312 2550 1220 1330000 1738.35
Sam
ple
23
50 2297 2530 1230 1300000 1766.92 40 2349 2520 1220 1300000 1806.92 41 2380 2530 1210 1320000 1803.03 42 2395 2530 1230 1300000 1842.31 43 2379 2580 1210 1370000 1736.50 44 2400 2500 1250 1250000 1920.00 45 2348 2600 1230 1370000 1713.87 46 2316 2530 1220 1310000 1767.94 47 2361 2580 1230 1350000 1748.89
Sam
ple
24
39 2368 2590 1230 1360000 1741.18 20 2427 2640 1260 1380000 1758.70 21 2419 2650 1290 1360000 1778.68 22 2378 2620 1230 1390000 1710.79 23 2309 2450 1190 1260000 1832.54 24 2333 2510 1210 1300000 1794.62 25 2317 2490 1200 1290000 1796.12 26 2311 2530 1220 1310000 1764.12 27 2389 2570 1240 1330000 1796.24 28 2385 2580 1250 1330000 1793.23
Sam
ple
26
29 2359 2590 1240 1350000 1747.41 10 2432 2640 1270 1370000 1775.18 11 2511 2660 1290 1370000 1832.85 12 2378 2610 1230 1380000 1723.19 13 2319 2430 1180 1250000 1855.20 14 2293 2510 1210 1300000 1763.85 15 2317 2470 1200 1270000 1824.41 16 2401 2540 1190 1350000 1778.52 17 2370 2590 1240 1350000 1755.56 18 2325 2560 1240 1320000 1761.36
Sam
ple
27
19 2369 2597 1220 1377000 1720.41
A 3
RESULTS OF TESTS SPECIMENS FOR
INITIAL RATE OF SUCTION OF BRICKS
176
Sample 1
Brick identifica
tion
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
16 2445 2485 221.15 100.75 22280.86 18905.86 1.795 2.116
2 2390 2420 216.50 98.80 21390.20 18015.20 1.403 1.665
11 2415 2450 218.30 99.70 21764.51 18389.51 1.608 1.903
4 2370 2400 216.05 98.30 21237.72 17862.72 1.413 1.679
9 2435 2485 221.45 102.25 22643.26 19268.26 2.208 2.595
17 2430 2465 220.05 100.75 22170.04 18795.04 1.579 1.862
19 2440 2490 220.10 100.10 22032.01 18657.01 2.269 2.680
3 2435 2455 217.55 98.80 21493.94 18118.94 0.930 1.104
7 2415 2450 217.10 100.00 21710.00 18335.00 1.612 1.909
8 2410 2435 216.60 99.80 21616.68 18241.68 1.157 1.370
Sample 2 1 2380 2410 216.55 99.55 21557.55 18182.55 1.392 1.650
12 2420 2455 217.95 99.75 21740.51 18365.51 1.610 1.906
10 2485 2515 218.60 99.65 21783.49 18408.49 1.377 1.630
18 2430 2450 216.30 97.95 21186.59 17811.59 0.944 1.123
6 2410 2445 217.00 99.80 21656.60 18281.60 1.616 1.914
15 2465 2500 216.30 99.15 21446.15 18071.15 1.632 1.937
5 2460 2490 217.50 99.65 21673.88 18298.88 1.384 1.639
20 2410 2435 217.50 99.15 21565.13 18190.13 1.159 1.374
14 2370 2400 217.75 99.65 21698.79 18323.79 1.383 1.637
13 2370 2410 217.50 99.90 21728.25 18353.25 1.841 2.179
Sample 3
35 2410 2440 217.30 99.20 21556.16 18181.16 1.39 1.650
69 2420 2455 217.35 99.70 21669.80 18294.80 1.62 1.913
63 2435 2490 216.95 99.25 21532.29 18157.29 2.55 3.029
37 2400 2425 216.40 99.25 21477.70 18102.70 1.16 1.381
68 2430 2470 208.50 101.20 21100.20 17725.20 1.90 2.257
40 2410 2445 217.00 99.25 21537.25 18162.25 1.63 1.927
29 2410 2445 217.25 99.65 21648.96 18273.96 1.62 1.915
41 2415 2450 217.10 99.60 21623.16 18248.16 1.62 1.918
71 2440 2485 218.10 100.05 21820.91 18445.91 2.06 2.440
39 2440 2475 216.95 99.35 21553.98 18178.98 1.62 1.925
Sample 4 42 2420 2455 217.10 100.10 21731.71 18356.71 1.61 1.907
82 2505 2542 219.50 101.50 22279.25 18904.25 1.66 1.957
98 2403 2439 218.50 100.35 21926.48 18551.48 1.64 1.941
92 2299 2338 214.10 98.40 21067.44 17692.44 1.85 2.204
89 2288 2336 215.75 99.85 21542.64 18167.64 2.23 2.642
81 2447 2482 218.50 100.5 21959.25 18584.25 1.59 1.883
85 2306 2344 214.80 97.65 20975.22 17600.22 1.81 2.159
41 2364 2403 218.15 101.25 22087.69 18712.69 1.77 2.084
88 2292 2327 214.05 98.00 20976.90 17601.90 1.67 1.988
100 2399 2436 217.50 100.60 21880.50 18505.50 1.69 1.999
177
Sample 5
Brick identifica
tion
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
99 2400 2436 218.00 100.00 21800.00 18425.00 1.65 1.954
91 2265 2302 214.10 97.95 20971.10 17596.10 1.76 2.103
97 2472 2516 218.20 99.70 21754.54 18379.54 2.02 2.394
90 2318 2347 214.15 98.30 21050.95 17675.95 1.38 1.641
84 2306 2340 214.75 93.90 20165.03 16790.03 1.69 2.025
95 2280 2323 214.50 99.05 21246.23 17871.23 2.02 2.406
86 2281 2326 215.50 99.00 21334.50 17959.50 2.11 2.506
87 2414 2452 216.95 100.50 21803.48 18428.48 1.74 2.062
96 2500 2548 220.75 102.30 22582.73 19207.73 2.13 2.499
43 2378 2430 218.60 102.20 22340.92 18965.92 2.33 2.742
Sample 6 20 2444 2484 218.50 100.65 21992.03 18617.03 1.82 2.149
19 2450 2484 219.25 100.02 21929.39 18554.39 1.55 1.832
76 2439 2477 217.10 100.00 21710.00 18335.00 1.75 2.073
15 2410 2440 217.20 98.90 21481.08 18106.08 1.40 1.657
17 2434 2478 218.25 101.00 22043.25 18668.25 2.00 2.357
51 2295 2338 215.70 68.5 14775.45 11400.45 2.91 3.772
61 2540 2575 217.70 100.45 21867.97 18492.97 1.60 1.893
11 2391 2428 217.45 100.05 21755.87 18380.87 1.70 2.013
16 2425 2457 217.30 99.85 21697.41 18322.41 1.47 1.746
78 2415 2447 217.55 99.70 21689.74 18314.74 1.48 1.747
Sample 7
74 2407 2451 216.85 99.50 21576.58 18201.58 2.04 2.417
79 2449 2493 219.75 101.25 22249.69 18874.69 1.98 2.331
80 2466 2510 219.55 101.20 22218.46 18843.46 1.98 2.335
62 2447 2490 218.30 100.80 22004.64 18629.64 1.95 2.308
75 2375 2411 217.00 98.95 21472.15 18097.15 1.68 1.989
73 2264 2310 214.90 99.5 21382.55 18007.55 2.15 2.554
72 2300 2341 214.50 98.50 21128.25 17753.25 1.94 2.309
77 2401 2438 217.00 100.25 21754.25 18379.25 1.70 2.013
71 2295 2334 217.05 99.80 21661.59 18286.59 1.80 2.133
60 2446 2485 217.45 99.60 21658.02 18283.02 1.80 2.133
Sample 8
49 2464 2508 217.60 100.60 21890.56 18515.56 2.01 2.376
9 2483 2533 219.70 101.20 22233.64 18858.64 2.25 2.651
10 2304 2357 219.40 100.95 22148.43 18773.43 2.39 2.823
46 2489 2535 220.60 102.10 22523.26 19148.26 2.04 2.402
1 2435 2462 216.40 98.80 21380.32 18005.32 1.26 1.500
56 2328 2359 216.10 98.9 21372.29 17997.29 1.45 1.722
52 2370 2406 217.15 99.75 21660.71 18285.71 1.66 1.969
2 2304 2333 215.65 97.50 21025.88 17650.88 1.38 1.643
14 2456 2498 218.75 101.05 22104.69 18729.69 1.90 2.242
3 2502 2554 220.75 102.40 22604.80 19229.80 2.30 2.704
178
Sample 9 Brick
identification
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
7 2420 2461 217.30 99.75 21675.68 18300.68 1.89 2.240
4 2430 2457 216.75 99.40 21544.95 18169.95 1.25 1.486
50 2358 2401 218.00 99.00 21582.00 18207.00 1.99 2.362
5 2497 2534 218.95 100.95 22103.00 18728.00 1.67 1.976
6 2372 2406 217.30 99.65 21653.95 18278.95 1.57 1.860
57 2483 2518 217.75 100.95 21981.86 18606.86 1.59 1.881
55 2412 2443 215.25 100.00 21525.00 18150.00 1.44 1.708
54 2412 2436 216.30 100.00 21630.00 18255.00 1.11 1.315
48 2506 2550 221.00 101.85 22508.85 19133.85 1.95 2.300
12 2493 2536 220.75 101.35 22373.01 18998.01 1.92 2.263
Sample 10 58 2446 2482 217.60 101.75 22140.80 18765.80 1.63 1.918
94 2240 2263 210.00 98.25 20632.50 17257.50 1.11 1.333
35 2398 2437 217.75 100.00 21775.00 18400.00 1.79 2.120
29 2503 2562 220.75 102.50 22626.88 19251.88 2.61 3.065
33 2445 2482 219.25 100.50 22034.63 18659.63 1.68 1.983
34 2495 2534 219.75 101.50 22304.63 18929.63 1.75 2.060
21 2411 2444 219.90 99.25 21825.08 18450.08 1.51 1.789
69 2496 2530 219.50 101.20 22213.40 18838.40 1.53 1.805
26 2318 2359 217.95 99.70 21729.62 18354.62 1.89 2.234
37 2289 2328 214.25 98.35 21071.49 17696.49 1.85 2.204
Sample 11
30 2458 2502 218.35 101.00 22053.35 18678.35 2.00 2.356
68 2412 2452 218.30 98.65 21535.30 18160.30 1.86 2.203
32 2543 2587 221.25 103.05 22799.81 19424.81 1.93 2.265
31 2502 2549 220.50 103.95 22920.98 19545.98 2.05 2.405
28 2509 2559 220.80 102.55 22643.04 19268.04 2.21 2.595
66 2439 2455 214.75 98.85 21228.04 17853.04 0.75 0.896
67 2306 2342 214.40 98.20 21054.08 17679.08 1.71 2.036
22 2477 2515 220.75 99.60 21986.70 18611.70 1.73 2.042
45 2333 2369 214.65 97.75 20982.04 17607.04 1.72 2.045
59 2451 2474 216.00 99.65 21524.40 18149.40 1.07 1.267
Sample 12
22 2443 2473 213.50 99.00 21136.50 17761.50 1.42 1.689
18 2443 2486 215.50 100.55 21668.53 18293.53 1.98 2.351
17 2459 2484 214.95 98.80 21237.06 17862.06 1.18 1.400
12 2449 2493 216.00 100.50 21708.00 18333.00 2.03 2.400
24 2449 2494 217.25 101.00 21942.25 18567.25 2.05 2.424
3 2449 2478 214.30 100.00 21430.00 18055.00 1.35 1.606
10 2436 2479 215.25 100.75 21686.44 18311.44 1.98 2.348
9 2452 2486 215.00 100.00 21500.00 18125.00 1.58 1.876
19 2409 2440 213.25 99.25 21165.06 17790.06 1.46 1.743
20 2449 2500 217.00 101.50 22025.50 18650.50 2.32 2.735
179
Sample 13 Brick
identification
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
15 2448 2485 215.40 100.00 21540.00 18165.00 1.72 2.037
23 2456 2498 216.00 100.45 21697.20 18322.20 1.94 2.292
7 2452 2483 215.00 99.50 21392.50 18017.50 1.45 1.721
14 2448 2482 215.10 99.25 21348.68 17973.68 1.59 1.892
13 2447 2492 215.70 100.75 21731.78 18356.78 2.07 2.451
16 2442 2482 215.00 100.25 21553.75 18178.75 1.86 2.200
21 2452 2488 215.00 99.35 21360.25 17985.25 1.69 2.002
8 2436 2461 214.35 97.95 20995.58 17620.58 1.19 1.419
11 2444 2474 214.75 98.50 21152.88 17777.88 1.42 1.687
5 2458 2510 216.25 100.75 21787.19 18412.19 2.39 2.824
Sample 14 38 2467 2511 217.25 100.25 21779.31 18404.31 2.02 2.391
37 2444 2479 215.00 99.50 21392.50 18017.50 1.64 1.943
32 2466 2511 216.75 100.60 21805.05 18430.05 2.06 2.442
41 2437 2475 214.90 99.50 21382.55 18007.55 1.78 2.110
27 2454 2482 214.65 99.25 21304.01 17929.01 1.31 1.562
47 2452 2493 216.25 100.75 21787.19 18412.19 1.88 2.227
45 2455 2489 215.25 99.65 21449.66 18074.66 1.59 1.881
34 2465 2507 217.10 101.25 21981.38 18606.38 1.91 2.257
26 2454 2488 214.80 99.65 21404.82 18029.82 1.59 1.886
28 2468 2522 215.75 100.40 21661.30 18286.30 2.49 2.953
Sample 15
36 2463 2492 214.80 99.75 21426.30 18051.30 1.35 1.607
42 2524 2555 214.65 99.65 21389.87 18014.87 1.45 1.721
48 2478 2533 217.30 101.55 22066.82 18691.82 2.49 2.942
43 2428 2453 215.35 98.00 21104.30 17729.30 1.18 1.410
25 2469 2513 216.00 100.75 21762.00 18387.00 2.02 2.393
44 2493 2534 217.00 100.75 21862.75 18487.75 1.88 2.218
31 2448 2470 212.65 98.55 20956.66 17581.66 1.05 1.251
39 2480 2512 215.90 99.50 21482.05 18107.05 1.49 1.767
29 2458 2501 215.50 100.00 21550.00 18175.00 2.00 2.366
40 2458 2492 215.00 98.80 21242.00 17867.00 1.60 1.903
Sample 16
94 2476 2479 215.50 98.55 21237.53 17862.53 0.14 0.168
60 2488 2510 215.25 99.40 21395.85 18020.85 1.03 1.221
79 2456 2494 216.00 100.00 21600.00 18225.00 1.76 2.085
76 2482 2505 215.75 99.00 21359.25 17984.25 1.08 1.279
75 2443 2467 214.50 97.60 20935.20 17560.20 1.15 1.367
86 2463 2494 214.30 100.00 21430.00 18055.00 1.45 1.717
96 2467 2496 216.00 98.55 21286.80 17911.80 1.36 1.619
58 2479 2511 216.00 99.70 21535.20 18160.20 1.49 1.762
65 2450 2471 215.50 98.25 21172.88 17797.88 0.99 1.180
71 2444 2483 216.35 100.50 21743.18 18368.18 1.79 2.123
180
Sample 17 Brick
identification
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
51 2457 2501 216.25 100.95 21830.44 18455.44 2.02 2.384
88 2439 2465 215.50 99.00 21334.50 17959.50 1.22 1.448
83 2462 2495 215.45 100.50 21652.73 18277.73 1.52 1.805
53 2450 2480 214.50 99.80 21407.10 18032.10 1.40 1.664
57 2457 2488 215.30 100.25 21583.83 18208.83 1.44 1.702
92 2488 2519 214.95 100.00 21495.00 18120.00 1.44 1.711
56 2480 2503 215.00 99.10 21306.50 17931.50 1.08 1.283
72 2458 2489 214.55 100.25 21508.64 18133.64 1.44 1.710
55 2472 2493 214.25 99.25 21264.31 17889.31 0.99 1.174
74 2489 2504 214.55 98.90 21219.00 17844.00 0.71 0.841
Sample 18 49 2468 2492 214.10 100.25 21463.53 18088.53 1.12 1.327
91 2480 2512 216.85 100.45 21782.58 18407.58 1.47 1.738
89 2433 2457 213.70 98.45 21038.77 17663.77 1.14 1.359
61 2450 2471 216.00 98.30 21232.80 17857.80 0.99 1.176
80 2451 2491 216.00 100.50 21708.00 18333.00 1.84 2.182
95 2477 2499 215.25 98.00 21094.50 17719.50 1.04 1.242
82 2432 2474 216.40 100.25 21694.10 18319.10 1.94 2.293
77 2494 2530 215.80 99.50 21472.10 18097.10 1.68 1.989
54 2443 2468 213.95 99.15 21213.14 17838.14 1.18 1.401
84 2453 2490 215.00 100.25 21553.75 18178.75 1.72 2.035
Sample 19
93 2452 2492 215.35 99.75 21481.16 18106.16 1.86 2.209
66 2449 2489 215.50 100.55 21668.53 18293.53 1.85 2.187
59 2437 2474 215.20 99.70 21455.44 18080.44 1.72 2.046
73 2446 2481 215.50 100.25 21603.88 18228.88 1.62 1.920
68 2443 2484 216.20 100.45 21717.29 18342.29 1.89 2.235
50 2445 2484 215.25 100.00 21525.00 18150.00 1.81 2.149
64 2442 2468 214.15 99.00 21200.85 17825.85 1.23 1.459
90 2441 2476 214.50 99.50 21342.75 17967.75 1.64 1.948
52 2440 2472 214.65 99.90 21443.54 18068.54 1.49 1.771
81 2442 2465 213.75 97.90 20926.13 17551.13 1.10 1.310
Sample 20
11 2340 2385 216.00 100.00 21600.00 18225.00 2.08 2.469
32 2345 2357 214.60 97.25 20869.85 17494.85 0.57 0.686
18 2359 2382 215.00 98.75 21231.25 17856.25 1.08 1.288
31 2351 2393 216.25 99.75 21570.94 18195.94 1.95 2.308
7 2363 2401 216.10 99.35 21469.54 18094.54 1.77 2.100
2 2396 2431 217.25 100.60 21855.35 18480.35 1.60 1.894
6 2380 2422 212.80 100.25 21333.20 17958.20 1.97 2.339
38 2338 2352 214.00 97.55 20875.70 17500.70 0.67 0.800
17 2328 2352 214.00 97.55 20875.70 17500.70 1.15 1.371
29 2344 2384 215.85 99.65 21509.45 18134.45 1.86 2.206
181
Sample 21 Brick
identification
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
13 2355 2392 216.25 100.00 21625.00 18250.00 1.71 2.027
25 2307 2326 214.00 98.50 21079.00 17704.00 0.90 1.073
39 2326 2368 215.55 100.10 21576.56 18201.56 1.95 2.307
44 2374 2421 217.85 102.00 22220.70 18845.70 2.12 2.494
22 2358 2378 215.00 98.80 21242.00 17867.00 0.94 1.119
26 2377 2423 216.80 100.00 21680.00 18305.00 2.12 2.513
19 2358 2374 215.00 98.00 21070.00 17695.00 0.76 0.904
41 2371 2411 217.50 100.30 21815.25 18440.25 1.83 2.169
30 2236 2269 215.25 100.15 21557.29 18182.29 1.53 1.815
36 2400 2437 218.50 100.75 22013.88 18638.88 1.68 1.985
Sample 22 40 2347 2388 215.55 99.45 21436.45 18061.45 1.91 2.270
3 2358 2403 216.80 100.25 21734.20 18359.20 2.07 2.451
37 2300 2334 214.75 98.25 21099.19 17724.19 1.61 1.918
20 2334 2381 217.00 101.00 21917.00 18542.00 2.14 2.535
40 2400 2433 217.75 100.50 21883.88 18508.88 1.51 1.783
35 2383 2410 216.25 98.50 21300.63 17925.63 1.27 1.506
47 2363 2371 214.25 97.35 20857.24 17482.24 0.38 0.458
45 2336 2367 215.25 98.00 21094.50 17719.50 1.47 1.749
16 2361 2373 214.45 97.00 20801.65 17426.65 0.58 0.689
4 2328 2387 216.25 100.50 21733.13 18358.13 2.71 3.214
Sample 23
24 2334 2372 216.26 99.50 21517.87 18142.87 1.77 2.094
1 2357 2403 216.90 101.60 22037.04 18662.04 2.09 2.465
27 2341 2379 216.00 99.95 21589.20 18214.20 1.76 2.086
5 2352 2391 216.85 100.50 21793.43 18418.43 1.79 2.117
15 2482 2499 213.75 98.00 20947.50 17572.50 0.81 0.967
9 2325 2359 216.00 99.95 21589.20 18214.20 1.57 1.867
14 2366 2422 217.00 101.50 22025.50 18650.50 2.54 3.003
46 2344 2359 214.00 97.25 20811.50 17436.50 0.72 0.860
8 2354 2404 216.00 99.75 21546.00 18171.00 2.32 2.752
28 2304 2336 216.00 98.00 21168.00 17793.00 1.51 1.798
Sample 24
61 2373 2430 220.70 102.50 22621.75 19246.75 2.52 2.962
62 2359 2428 220.65 102.60 22638.69 19263.69 3.05 3.582
96 2393 2426 216.15 99.15 21431.27 18056.27 1.54 1.828
79 2384 2419 215.75 99.75 21521.06 18146.06 1.63 1.929
76 2310 2360 216.15 100.55 21733.88 18358.88 2.30 2.723
73 2338 2384 216.25 99.25 21462.81 18087.81 2.14 2.543
86 2308 2359 217.25 99.40 21594.65 18219.65 2.36 2.799
70 2356 2412 220.75 102.45 22615.84 19240.84 2.48 2.910
71 2351 2369 216.55 99.90 21633.35 18258.35 0.83 0.986
55 2298 2321 213.90 98.75 21122.63 17747.63 1.09 1.296
182
Sample 25 Brick
identification
Dry mass
(md) gm
Wet mass
(mw) gm
length (mm)
l
Width (mm)
b
Immersed area
(mm2) Agross
Immersed area
(mm2) Anet
IRSgross 1000(mw – md)/Agross
kg/m2.min
IRSnet 1000(m2 –m1)/Anet
kg/m2.min
78 2313 2362 216.30 100.25 21684.08 18309.08 2.26 2.676
53 2363 2380 215.00 98.75 21231.25 17856.25 0.80 0.952
80 2379 2427 217.25 101.25 21996.56 18621.56 2.18 2.578
89 2330 2384 217.05 100.50 21813.53 18438.53 2.48 2.929
88 2313 2360 216.25 100.50 21733.13 18358.13 2.16 2.560
77 2288 2319 215.50 99.50 21442.25 18067.25 1.45 1.716
94 2316 2365 215.90 99.75 21536.03 18161.03 2.28 2.698
85 2332 2370 217.30 99.35 21588.76 18213.76 1.76 2.086
74 2377 2392 217.00 99.50 21591.50 18216.50 0.69 0.823
82 2353 2402 216.85 100.25 21739.21 18364.21 2.25 2.668
Sample 26 52 2321 2347 215.25 98.25 21148.31 17773.31 1.23 1.463
50 2342 2346 214.55 98.75 21186.81 17811.81 0.19 0.225
64 2398 2411 216.50 99.15 21465.98 18090.98 0.61 0.719
84 2299 2347 217.75 100.00 21775.00 18400.00 2.20 2.609
56 2357 2375 215.75 99.75 21521.06 18146.06 0.84 0.992
93 2318 2368 216.90 100.10 21711.69 18336.69 2.30 2.727
67 2351 2407 220.50 102.00 22491.00 19116.00 2.49 2.929
90 2361 2380 215.75 97.85 21111.14 17736.14 0.90 1.071
91 2329 2380 215.85 100.30 21649.76 18274.76 2.36 2.791
59 2302 2321 216.90 99.65 21614.09 18239.09 0.88 1.042
Sample 27
57 2393 2416 217.50 100.45 21847.88 18472.88 1.05 1.245
81 2323 2372 216.30 100.25 21684.08 18309.08 2.26 2.676
69 2365 2384 216.00 99.25 21438.00 18063.00 0.89 1.052
66 2387 2392 215.65 99.10 21370.92 17995.92 0.23 0.278
68 2399 2418 216.25 99.40 21495.25 18120.25 0.88 1.049
79 2363 2403 216.60 99.25 21497.55 18122.55 1.86 2.207
65 2312 2339 214.00 98.00 20972.00 17597.00 1.29 1.534
58 2377 2399 217.00 99.90 21678.30 18303.30 1.01 1.202
54 2346 2370 216.95 100.00 21695.00 18320.00 1.11 1.310
63 2301 2348 215.00 99.35 21360.25 17985.25 2.20 2.613
A 4
RESULTS OF TESTS SPECIMENS FOR
WATER ABSORPTION OF BRICKS
184
Sample 1 Sample 2
Brick Dry mass Saturated mass
A (Water absorption)%
identification W1(gm) W2 (gm)
A= 100( W2-W1)/W1
2 2390 2590 8.37 9 2435 2760 13.35
11 2415 2665 10.35 3 2435 2650 8.83
15 2465 2700 9.53 17 2430 2720 11.93 12 2420 2675 10.54 18 2430 2625 8.02 6 2410 2690 11.62
16 2445 2740 12.07 Sample 4
82 2505 2795 11.58 95 2280 2567 12.59 85 2306 2553 10.71 84 2306 2555 10.80 92 2299 2565 11.57 98 2403 2692 12.03 81 2447 2712 10.83 100 2399 2669 11.25 89 2288 2594 13.37 42 2420 2676 10.58
Sample 6
19 2450 2715 10.82 71 2295 2596 13.12 79 2449 2752 12.37 72 2300 2586 12.43 61 2540 2816 10.87 60 2446 2727 11.49 15 2410 2652 10.04 62 2448 2740 11.93 78 2415 2687 11.26 75 2376 2642 11.20
Sample 8
9 2483 2790 12.36 55 2412 2662 10.36 4 2430 2676 10.12
10 2304 2589 12.37 14 2456 2740 11.56 56 2328 2576 10.65 12 2493 2792 11.99 48 2506 2795 11.53 5 2497 2803 12.25
54 2412 2664 10.45
Brick Dry mass Saturated mass
A (Water absorption)%
identification W1(gm) W2 (gm) A= 100( W2-W1)/W1
7 2415 2670 10.559 5 2460 2710 10.163 1 2380 2640 10.924 13 2370 2670 12.658 8 2410 2640 9.544 14 2370 2645 11.603 4 2370 2625 10.759 20 2410 2665 10.581 19 2440 2775 13.730 10 2485 2745 10.463
Sample 3 39 2440 2695 10.45 69 2420 2685 10.95 35 2410 2680 11.20 41 2415 2695 11.59 37 2400 2655 10.63 29 2410 2685 11.41 40 2410 2670 10.79 68 2430 2745 12.96 63 2435 2735 12.32 71 2440 2710 11.07
Sample 5 99 2400 2684 11.83 86 2281 2576 12.93 97 2472 2774 12.22 43 2378 2706 13.79 91 2265 2517 11.13 90 2318 2559 10.40 96 2500 2810 12.40 87 2414 2684 11.18 41 2364 2658 12.44 88 2292 2542 10.91
Sample 7 11 2386 2673 12.03 77 2401 2676 11.45 16 2425 2688 10.85 76 2439 2722 11.60 20 2444 2731 11.74 17 2434 2734 12.33 74 2407 2701 12.21 80 2466 2786 12.98 73 2263 2556 12.95 51 2296 2570 11.93
185
Sample 9 Sample 10 Brick Dry mass Saturated
mass A (Water absorption)%
identification W1(gm) W2 (gm)
A= 100( W2-W1)/W1
22 2464 2760 12.01 58 2489 2747 10.37 37 2304 2572 11.63 66 2422 2665 10.03 67 2307 2577 11.70 26 2322 2619 12.79 59 2450 2702 10.29 45 2382 2606 9.40 28 2518 2824 12.15 68 2384 2707 13.55
Sample 12
13 2447 2738 11.89 9 2452 2729 11.30 12 2449 2744 12.05 20 2449 2760 12.70 3 2449 2706 10.49 7 2452 2710 10.52 19 2409 2659 10.38 24 2449 2761 12.74 11 2444 2699 10.43 10 2436 2711 11.29
Sample 14
34 2465 2770 12.37 41 2437 2709 11.16 32 2466 2767 12.21 27 2454 2713 10.55 38 2467 2766 12.12 48 2478 2796 12.83 45 2455 2728 11.12 40 2458 2720 10.66 29 2458 2736 11.31 37 2444 2713 11.01
Sample 16
75 2482 2672 7.66 86 2463 2717 10.31 91 2480 2761 11.33 71 2444 2738 12.03 65 2450 2687 9.67 79 2456 2735 11.36 80 2451 2734 11.55 96 2467 2721 10.30 83 2462 2729 10.84 58 2479 2723 9.84
Brick Dry mass Saturated mass
A (Water absorption)%
identification W1(gm) W2 (gm) A= 100( W2-W1)/W1
49 2464 2757 11.89 46 2489 2805 12.70 2 2304 2562 11.20 1 2435 2670 9.65 52 2370 2644 11.56 7 2420 2709 11.94 57 2483 2759 11.12 3 2502 2821 12.75 50 2358 2668 13.15 6 2372 2657 12.02
Sample 11 29 2503 2832 13.14 21 2411 2687 11.45 31 2502 2819 12.67 34 2495 2797 12.10 94 2240 2487 11.03 30 2458 2759 12.25 33 2445 2742 12.15 69 2496 2774 11.14 35 2398 2680 11.76 32 2543 2836 11.52
Sample 13 22 2443 2684 9.86 8 2436 2654 8.95 21 2452 2722 11.01 15 2448 2727 11.40 23 2456 2745 11.77 17 2459 2710 10.21 16 2442 2724 11.55 18 2443 2735 11.95 5 2458 2759 12.25 14 2448 2712 10.78
Sample 15 47 2452 2743 11.87 44 2493 2783 11.63 42 2524 2789 10.50 43 2428 2678 10.30 36 2463 2736 11.08 25 2469 2760 11.79 31 2448 2672 9.15 26 2454 2720 10.84 28 2468 2757 11.71 39 2480 2728 10.00
186
Sample 17 Sample 18 Brick Dry mass Saturated
mass A (Water absorption)%
identification W1(gm) W2 (gm)
A= 100( W2-W1)/W1
88 2439 2692 10.37 93 2452 2703 10.24 84 2453 2724 11.05 92 2488 2744 10.29 66 2449 2731 11.51 68 2443 2734 11.91 73 2446 2725 11.41 59 2437 2715 11.41 81 2442 2673 9.46 53 2450 2709 10.57
Sample 20
19 2358 2560 8.57 44 2374 2697 13.61 30 2236 2496 11.63 41 2371 2665 12.40 36 2400 2665 11.04 7 2363 2634 11.47 38 2338 2536 8.47 2 2396 2675 11.64 25 2307 2537 9.97 29 2344 2618 11.69
Sample 22
69 2365 2609 10.32 66 2387 2617 9.64 58 2377 2649 11.44 63 2301 2556 11.08 79 2363 2614 10.62 61 2373 2705 13.99 70 2356 2670 13.33 71 2351 2612 11.10 65 2312 2540 9.86 96 2393 2633 10.03
Sample 24
57 2393 2687 12.29 56 2357 2615 10.95 93 2318 2620 13.03 85 2332 2626 12.61 84 2299 2609 13.48 94 2316 2604 12.44 82 2353 2653 12.75 67 2351 2689 14.38 54 2346 2630 12.11 74 2377 2660 11.91
Brick Dry mass Saturated mass
A (Water absorption)%
identification W1(gm) W2 (gm) A= 100( W2-W1)/W1
74 2489 2709 8.84 61 2450 2675 9.18 76 2482 2712 9.27 60 2488 2707 8.80 49 2468 2718 10.13 55 2472 2709 9.59 95 2477 2706 9.25 89 2433 2655 9.12 94 2476 2711 9.49 72 2458 2713 10.37
Sample 19 57 2457 2731 11.15 52 2440 2704 10.82 51 2457 2754 12.09 56 2480 2712 9.35 77 2494 2740 9.86 54 2443 2690 10.11 64 2442 2692 10.24 90 2441 2696 10.45 82 2432 2728 12.17 50 2445 2724 11.41
Sample 21 6 2380 2680 12.61 18 2374 2579 8.64 13 2355 2641 12.14 31 2351 2627 11.74 22 2358 2586 9.67 11 2341 2624 12.09 26 2377 2663 12.03 32 2345 2547 8.61 39 2326 2600 11.78 17 2328 2520 8.25
Sample 23 55 2298 2512 9.31 78 2313 2617 13.14 73 2338 2618 11.98 79 2384 2631 10.36 86 2308 2602 12.74 76 2310 2609 12.94 53 2363 2583 9.31 81 2323 2619 12.74 62 2308 2620 13.52 68 2399 2671 11.34
187
Sample 25 Sample 26 Brick Dry mass Saturated
mass A (Water absorption)%
identification W1(gm) W2 (gm)
A= 100( W2-W1)/W1
20 2334 2607 11.70 35 2383 2572 7.93 15 2482 2566 9.34 45 2336 2571 10.06 37 2300 2673 11.65 1 2357 2642 12.09 14 2366 2569 8.58 27 2341 2557 9.23 47 2363 2624 11.05 3 2358 2665 13.02
Brick Dry mass Saturated mass
A (Water absorption)%
identification W1(gm) W2 (gm) A= 100( W2-W1)/W1
88 2313 2607 12.71 90 2361 2572 8.94 50 2342 2566 9.56 59 2302 2571 11.69 80 2379 2673 12.36 89 2330 2642 13.39 52 2321 2569 10.69 77 2288 2557 11.76 91 2329 2624 12.67 64 2398 2665 11.13
Sample 27 5 2352 2647 12.54 9 2325 2608 12.17 24 2334 2614 12.00 16 2361 2548 7.92 4 2328 2623 12.67 8 2354 2646 12.40 40 2400 2672 11.33 46 2344 2551 8.83 28 2304 2568 11.46 41 2347 2623 11.76
A 5
RESULTS OF TESTS SPECIMENS FOR
COMPRESSIVE STRENGTH OF BRICKS
189
FACING BRICK – BED FACE Sample 1 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2 Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
18 216.10 98.50 21285.85 216.20 98.50 21295.70 21285.85 894.10 42.00
12 212.85 100.00 21285.00 217.85 99.90 21763.22 21285.00 988.80 46.46
14 217.75 99.35 21633.46 217.90 99.65 21713.74 21633.46 944.90 43.68
10 218.95 99.95 21884.05 218.75 99.65 21798.44 21798.44 1036.90 47.57
17 219.50 100.55 22070.73 219.40 100.75 22104.55 22070.73 840.90 38.10
11 217.25 99.40 21594.65 217.10 99.85 21677.44 21594.65 820.90 38.01
16 219.50 100.25 22004.88 220.10 100.20 22054.02 22004.88 776.90 35.31
6 217.20 99.80 21676.56 217.45 99.65 21668.89 21668.89 913.90 42.18
2 215.20 97.60 21003.52 215.55 98.20 21167.01 21003.52 694.90 33.08
8 216.60 98.70 21378.42 216.30 98.65 21338.00 21338.00 844.90 39.60
Sample 2
71 217.05 100.50 21813.53 218.15 100.75 21978.61 21813.53 1064.30 48.79
63 219.25 101.00 22144.25 219.50 101.10 22191.45 22144.25 957.30 43.23
39 217.30 99.50 21621.35 217.35 99.45 21615.46 21615.46 964.30 44.61
68 219.90 101.45 22308.86 220.50 101.35 22347.68 22308.86 977.00 43.79
69 217.50 99.85 21717.38 217.05 100.05 21715.85 21715.85 1091.90 50.28
35 217.55 99.10 21559.21 217.70 99.00 21552.30 21552.30 1106.00 51.32
40 216.95 99.25 21532.29 217.00 99.15 21515.55 21515.55 1113.00 51.73
41 217.50 99.55 21652.13 217.10 99.50 21601.45 21601.45 1187.00 54.95
29 217.00 100.00 21700.00 217.20 99.85 21687.42 21687.42 965.00 44.50
37 217.00 99.40 21569.80 216.45 99.25 21482.66 21482.66 1159.90 53.99
Sample 3
96 220.85 102.25 22581.91 221.25 102.25 22622.81 22581.91 803.40 35.58
91 214.00 97.95 20961.30 214.00 97.65 20897.10 20897.10 874.10 41.83
90 214.25 98.35 21071.49 214.20 98.40 21077.28 21071.49 942.30 44.72
43 219.20 101.95 22347.44 219.20 101.80 22314.56 22314.56 797.90 35.76
41 218.20 101.30 22103.66 218.00 101.30 22083.40 22083.40 684.80 31.01
88 214.35 97.95 20995.58 214.40 97.15 20828.96 20828.96 947.80 45.50
87 217.20 100.45 21817.74 217.75 100.25 21829.44 21817.74 885.90 40.60
82 219.90 101.70 22363.83 220.20 101.50 22350.30 22350.30 793.90 35.52
42 217.45 100.15 21777.62 217.00 100.10 21721.70 21721.70 930.90 42.86
89 215.95 99.75 21541.01 215.50 99.65 21474.58 21474.58 776.90 36.18
Sample 4
51 216.00 98.60 21297.60 216.10 98.80 21350.68 21297.60 777.90 36.53
80 219.50 101.10 22191.45 219.55 101.45 22273.35 22191.45 912.90 41.14
15 215.25 98.75 21255.94 214.30 98.50 21108.55 21108.55 1020.90 48.36
62 218.60 101.75 22242.55 219.40 101.88 22352.47 22242.55 855.80 38.48
78 218.20 101.70 22190.94 218.65 101.20 22127.38 22127.38 676.70 30.58
11 215.35 97.66 21031.08 214.50 97.59 20933.06 20933.06 614.70 29.37
73 217.80 101.35 22074.03 217.35 100.15 21767.60 21767.60 589.60 27.09
20 219.00 101.85 22305.15 220.01 101.45 22320.01 22305.15 853.70 38.27
75 217.95 100.65 21936.67 217.14 100.55 21833.43 21833.43 777.60 35.62
72 215.55 99.95 21544.22 215.75 99.95 21564.21 21544.22 639.60 29.69
190
Sample 5 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
4 216.85 98.95 21457.31 216.10 98.80 21350.68 21350.68 1203.00 56.34
3 221.30 102.65 22716.45 221.00 102.40 22630.40 22630.40 928.00 41.01
57 217.70 101.75 22150.98 217.80 101.65 22139.37 22139.37 1276.90 57.68
48 221.20 101.45 22440.74 221.30 101.50 22461.95 22440.74 938.00 41.80
12 220.55 101.35 22352.74 220.30 101.40 22338.42 22338.42 761.90 34.11
55 215.30 100.00 21530.00 215.25 99.98 21520.70 21520.70 1000.90 46.51
6 217.25 99.50 21616.38 217.35 99.54 21635.02 21616.38 1123.80 51.99
7 217.20 99.65 21643.98 217.30 99.55 21632.22 21632.22 1275.80 58.98
10 219.45 100.95 22153.48 219.40 100.55 22060.67 22060.67 882.70 40.01
9 219.50 101.35 22246.33 219.35 101.50 22264.03 22246.33 935.80 42.07
Sample 6
32 220.00 102.95 22649.00 221.00 103.75 22928.75 22649.00 903.90 39.91
31 220.65 102.25 22561.46 220.60 102.10 22523.26 22523.26 879.00 39.03
69 219.35 101.15 22187.25 219.10 101.30 22194.83 22187.25 1015.90 45.79
35 217.70 100.00 21770.00 217.70 99.90 21748.23 21748.23 1055.90 48.55
34 220.25 101.75 22410.44 219.85 101.75 22369.74 22369.74 904.00 40.41
33 219.25 100.95 22133.29 219.30 101.25 22204.13 22133.29 958.00 43.28
29 221.25 102.50 22678.13 221.00 102.75 22707.75 22678.13 877.90 38.71
21 220.00 99.25 21835.00 219.85 99.30 21831.11 21831.11 1066.00 48.83
94 210.00 98.35 20653.50 209.80 98.70 20707.26 20653.50 1126.90 54.56
68 218.65 98.70 21580.76 218.45 98.50 21517.33 21517.33 1238.90 57.58
Sample 7
21 215.50 99.35 21409.93 215.50 99.55 21453.03 21409.93 1322.10 61.75
18 215.60 100.45 21657.02 215.75 100.50 21682.88 21657.02 1280.10 59.11
13 215.75 100.75 21736.81 215.95 100.75 21756.96 21736.81 1190.10 54.75
8 214.00 98.75 21132.50 214.00 97.50 20865.00 20865.00 1512.10 72.47
15 215.75 100.00 21575.00 215.25 100.00 21525.00 21525.00 1292.10 60.03
23 215.75 100.50 21682.88 216.00 100.50 21708.00 21682.88 1291.10 59.54
22 213.65 99.25 21204.76 213.75 99.15 21193.31 21193.31 1348.10 63.61
17 215.00 99.00 21285.00 215.00 98.75 21231.25 21231.25 1404.10 66.13
10 215.25 100.00 21525.00 215.40 100.25 21593.85 21525.00 1007.10 46.79
5 216.50 100.70 21801.55 216.25 100.75 21787.19 21787.19 967.10 44.39
Sample 8
44 217.00 100.85 21884.45 216.95 100.75 21857.71 21857.71 993.70 45.46
47 215.95 100.75 21756.96 216.25 100.75 21787.19 21756.96 1112.70 51.14
28 215.85 100.25 21638.96 215.80 100.25 21633.95 21633.95 1087.70 50.28
29 215.50 100.25 21603.88 215.45 100.35 21620.41 21603.88 1077.80 49.89
26 215.25 99.75 21471.19 214.75 99.80 21432.05 21432.05 617.80 28.83
37 215.00 99.40 21371.00 215.10 99.50 21402.45 21371.00 1183.80 55.39
39 215.75 99.25 21413.19 214.95 99.45 21376.78 21376.78 1208.80 56.55
40 214.85 98.90 21248.67 215.00 98.80 21242.00 21242.00 1127.80 53.09
31 213.00 98.75 21033.75 213.00 98.55 20991.15 20991.15 1435.30 68.38
45 215.25 99.75 21471.19 215.25 99.90 21503.48 21471.19 1142.30 53.20
191
Sample 9
Dimension 1 (mm) Dimension 2 (mm) Brick Identific
ation Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
43 215.45 98.00 21114.10 215.50 97.90 21097.45 21097.45 1128.30 53.48
38 217.30 100.25 21784.33 216.75 100.35 21750.86 21750.86 916.20 42.12
25 216.25 101.00 21841.25 216.25 100.65 21765.56 21765.56 1169.80 53.75
48 217.35 101.30 22017.56 217.45 101.60 22092.92 22017.56 1066.80 48.45
42 214.30 99.75 21376.43 214.50 99.75 21396.38 21376.43 1020.30 47.73
32 216.75 100.50 21783.38 216.75 100.50 21783.38 21783.38 1098.30 50.42
36 216.70 99.85 21637.50 215.00 99.85 21467.75 21467.75 1089.30 50.74
27 214.90 99.40 21361.06 214.75 99.35 21335.41 21335.41 1161.90 54.46
41 214.95 99.55 21398.27 214.90 99.65 21414.79 21398.27 1299.80 60.74
34 217.30 101.50 22055.95 217.25 101.35 22018.29 22018.29 1049.80 47.68
Sample 10
50 215.25 99.80 21481.95 215.35 99.75 21481.16 21481.16 1035.60 48.21
54 214.00 99.00 21186.00 213.95 99.20 21223.84 21186.00 1105.60 52.19
77 215.95 99.60 21508.62 215.90 99.75 21536.03 21508.62 1126.60 52.38
82 216.50 100.40 21736.60 216.65 100.25 21719.16 21719.16 881.60 40.59
64 214.15 99.25 21254.39 214.25 99.10 21232.18 21232.18 1177.50 55.46
56 215.25 99.00 21309.75 215.00 99.15 21317.25 21309.75 1139.50 53.47
51 216.45 100.75 21807.34 215.25 101.00 21740.25 21740.25 1091.50 50.21
52 215.00 99.80 21457.00 214.75 99.85 21442.79 21442.79 1007.50 46.99
57 215.65 100.25 21618.91 215.45 100.15 21577.32 21577.32 1077.50 49.94
59 215.25 99.75 21471.19 215.15 99.70 21450.46 21450.46 1043.50 48.65
Sample 11
39 215.50 100.00 21550.00 215.45 100.00 21545.00 21545.00 977.00 45.35
13 216.15 99.80 21571.77 216.00 100.40 21686.40 21571.77 931.00 43.16
31 216.45 99.95 21634.18 216.25 100.00 21625.00 21625.00 922.00 42.64
18 215.00 98.85 21252.75 215.35 98.30 21168.91 21168.91 1132.00 53.47
6 217.90 100.25 21844.48 218.25 100.50 21934.13 21844.48 838.00 38.36
17 214.00 97.50 20865.00 214.25 97.50 20889.38 20865.00 842.00 40.35
29 215.75 99.75 21521.06 215.75 99.75 21521.06 21521.06 886.00 41.17
25 214.65 98.25 21089.36 214.00 98.25 21025.50 21025.50 1025.00 48.75
32 215.35 97.75 21050.46 214.40 97.70 20946.88 20946.88 928.00 44.30
26 216.90 100.00 21690.00 216.75 100.20 21718.35 21690.00 945.00 43.57
Sample 12
69 216.10 99.15 21426.32 216.25 99.15 21441.19 21426.32 1109.00 51.76
62 221.00 102.60 22674.60 220.75 102.75 22682.06 22674.60 797.00 35.15
65 214.25 98.00 20996.50 214.25 97.50 20889.38 20889.38 998.00 47.78
76 216.30 100.50 21738.15 216.25 100.50 21733.13 21733.13 869.00 39.99
86 217.55 99.30 21602.72 217.50 99.40 21619.50 21602.72 904.00 41.85
96 216.35 99.75 21580.91 216.00 99.25 21438.00 21438.00 971.00 45.29
81 216.35 99.75 21580.91 216.45 99.75 21590.89 21580.91 914.00 42.35
71 216.50 99.85 21617.53 216.45 99.40 21515.13 21515.13 1270.00 59.03
70 220.75 102.45 22615.84 220.75 102.50 22626.88 22615.84 769.00 34.00
61 220.50 102.45 22590.23 220.80 102.50 22632.00 22590.23 815.00 36.08
192
Sample 13 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
64 216.50 99.15 21465.98 216.25 99.10 21430.38 21430.38 1374.00 64.11
74 217.20 99.40 21589.68 217.00 99.50 21591.50 21589.68 1056.00 48.91
88 216.35 100.45 21732.36 216.35 100.55 21753.99 21732.36 889.00 40.91
90 215.25 97.80 21051.45 215.65 97.50 21025.88 21025.88 1216.00 57.83
54 216.75 100.00 21675.00 216.75 100.05 21685.84 21675.00 1109.00 51.16
84 217.70 100.25 21824.43 218.05 99.90 21783.20 21783.20 838.00 38.47
67 220.60 102.30 22567.38 220.55 102.00 22496.10 22496.10 881.00 39.16
85 217.35 99.50 21626.33 217.75 99.50 21666.13 21626.33 924.00 42.73
82 216.70 100.10 21691.67 216.95 100.00 21695.00 21691.67 856.00 39.46
77 215.25 99.75 21471.19 215.30 99.75 21476.18 21471.19 790.00 36.79
Sample 14
40 215.75 99.25 21413.19 216.10 99.30 21458.73 21413.19 844.00 39.41
46 214.35 97.75 20952.71 214.00 97.40 20843.60 20843.60 865.00 41.50
28 215.95 93.00 20083.35 216.00 98.00 21168.00 20083.35 1007.00 50.14
5 217.10 100.25 21764.28 217.00 100.45 21797.65 21764.28 905.00 41.58
4 216.30 100.70 21781.41 216.25 100.55 21743.94 21743.94 866.00 39.83
3 216.70 100.00 21670.00 216.50 100.00 21650.00 21650.00 891.00 41.15
16 215.00 97.00 20855.00 214.65 97.00 20821.05 20821.05 1179.00 56.63
47 214.25 97.45 20878.66 214.15 97.35 20847.50 20847.50 1013.00 48.59
27 215.90 99.70 21525.23 216.25 99.75 21570.94 21525.23 936.00 43.48
14 217.10 101.10 21948.81 217.00 101.30 21982.10 21948.81 892.00 40.64
FACING BRICK – STRETCHER FACE Sample 1
27 218.00 67.50 14715.00 214.90 67.45 14495.01 14495.01 570.00 39.32
38 217.00 67.30 14604.10 216.50 66.75 14451.38 14451.38 569.00 39.37
30 217.55 64.50 14031.98 217.30 64.50 14015.85 14015.85 488.00 34.82
3 217.25 67.75 14718.69 217.00 68.00 14756.00 14718.69 573.00 38.93
60 217.10 68.35 14838.79 217.15 68.00 14766.20 14766.20 581.00 39.35
43 217.95 66.90 14580.86 217.50 67.00 14572.50 14572.50 540.00 37.06
66 216.85 67.30 14594.01 216.85 68.00 14745.80 14594.01 538.00 36.86
25 218.00 67.10 14627.80 217.65 66.00 14364.90 14364.90 529.00 36.83
23 216.50 67.90 14700.35 216.50 68.00 14722.00 14700.35 544.00 37.01
44 217.70 67.75 14749.18 217.00 67.75 14701.75 14701.75 490.00 33.33
Sample 2
74 217.00 68.80 14929.60 217.55 70.00 15228.50 14929.60 504.90 33.82
76 217.25 68.75 14935.94 217.00 68.00 14756.00 14756.00 394.80 26.76
77 217.30 68.75 14939.38 217.25 68.70 14925.08 14925.08 499.80 33.49
61 217.80 69.25 15082.65 217.95 69.50 15147.53 15082.65 491.80 32.61
79 220.65 67.20 14827.68 220.75 67.50 14900.63 14827.68 427.90 28.86
97 218.30 68.80 15019.04 218.55 70.00 15298.50 15019.04 569.90 37.95
92 214.85 68.00 14609.80 214.25 67.75 14515.44 14515.44 455.90 31.41
100 217.10 67.85 14730.24 217.25 67.70 14707.83 14707.83 410.00 27.88
98 218.50 68.00 14858.00 218.95 67.50 14779.13 14779.13 456.00 30.85
95 219.75 68.60 15074.85 219.75 68.20 14986.95 14986.95 404.00 26.96
193
FACING BRICK – STRETCHER FACE Sample 3 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
37 214.50 68.55 14703.98 214.25 68.00 14569.00 14569.00 513.90 35.27
66 214.30 66.20 14186.66 214.25 66.80 14311.90 14186.66 535.00 37.71
59 216.00 68.00 14688.00 216.00 67.55 14590.80 14590.80 634.00 43.45
30 218.25 69.50 15168.38 217.75 69.65 15166.29 15166.29 516.00 34.02
28 220.55 69.00 15217.95 220.75 68.25 15066.19 14482.86 497.80 34.37
52 217.00 66.85 14506.45 217.15 66.55 14451.33 14451.33 429.80 29.74
46 220.65 68.05 15015.23 220.45 68.00 14990.60 14990.60 336.60 22.45
5 219.25 69.25 15183.06 219.35 69.30 15200.96 15183.06 522.80 34.43
1 216.50 66.95 14494.68 216.55 66.88 14482.86 14482.86 506.80 34.99
4 214.25 66.35 14215.49 214.20 66.40 14222.88 14215.49 503.80 35.44
Sample 4
9 215.00 67.20 14448.00 215.00 67.00 14405.00 14405.00 495.10 34.37
16 215.10 67.20 14454.72 214.75 67.00 14388.25 14388.25 514.10 35.73
12 216.00 67.25 14526.00 215.70 66.95 14441.12 14441.12 479.10 33.18
14 215.00 67.25 14458.75 214.75 66.70 14323.83 14323.83 576.20 40.23
11 215.00 67.35 14480.25 214.40 67.00 14364.80 14364.80 496.20 34.54
37 214.50 68.55 14703.98 214.25 68.00 14569.00 14569.00 513.90 35.27
66 214.30 66.20 14186.66 214.25 66.80 14311.90 14186.66 535.00 37.71
59 216.00 68.00 14688.00 216.00 67.55 14590.80 14590.80 634.00 43.45
30 218.25 69.50 15168.38 217.75 69.65 15166.29 15166.29 516.00 34.02
28 220.55 69.00 15217.95 220.75 68.25 15066.19 14482.86 397.80 27.47
Sample 5
49 213.90 67.00 14331.30 214.00 62.75 13428.50 13428.50 549.60 40.93
60 215.25 67.00 14421.75 215.00 66.20 14233.00 14233.00 704.60 49.50
55 214.00 67.00 14338.00 213.80 67.00 14324.60 14324.60 639.50 44.64
76 215.25 66.75 14367.94 215.40 66.85 14399.49 14367.94 651.50 45.34
72 214.00 67.00 14338.00 214.15 67.00 14348.05 14338.00 557.50 38.88
95 214.75 67.00 14388.25 215.00 67.50 14512.50 14388.25 644.50 44.79
58 215.75 67.00 14455.25 215.90 67.25 14519.28 14455.25 635.50 43.96
94 215.25 67.00 14421.75 215.25 67.00 14421.75 14421.75 513.50 35.61
89 213.25 66.00 14074.50 213.25 66.25 14127.81 14074.50 774.50 55.03
61 215.25 67.00 14421.75 214.85 67.00 14394.95 14394.95 618.50 42.97
Sample 6
90 213.85 67.00 14327.95 214.00 66.75 14284.50 14284.50 541.50 37.91
68 216.00 67.45 14569.20 215.75 67.70 14606.28 14569.20 412.50 28.31
73 215.15 67.25 14468.84 215.35 67.45 14525.36 14468.84 487.50 33.69
92 214.55 67.75 14535.76 214.85 67.55 14513.12 14513.12 551.50 38.00
53 214.50 66.90 14350.05 214.25 66.85 14322.61 14322.61 487.50 34.04
81 213.95 66.50 14227.68 214.00 66.90 14316.60 14227.68 680.50 47.83
84 215.00 67.00 14405.00 215.30 67.30 14489.69 14405.00 539.50 37.45
93 215.25 66.75 14367.94 214.90 66.25 14237.13 14237.13 539.50 37.89
66 215.20 67.00 14418.40 215.25 67.45 14518.61 14418.40 506.50 35.13
88 215.40 66.90 14410.26 215.25 67.00 14421.75 14421.75 531.50 36.85
194
FACING BRICK – STRETCHER FACE Sample 7 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
11 215.55 67.50 14549.63 215.50 67.65 14578.58 14549.63 323.00 22.20
2 217.00 67.75 14701.75 217.25 68.00 14773.00 14701.75 460.00 31.29
22 215.00 67.00 14405.00 214.85 66.75 14341.24 14341.24 653.00 45.53
19 214.70 67.20 14427.84 214.55 66.75 14321.21 14321.21 541.00 37.78
44 217.95 68.25 14875.09 217.55 68.25 14847.79 14847.79 285.00 19.19
30 214.85 63.10 13557.04 214.90 65.75 14129.68 13557.04 407.00 30.02
41 217.40 67.85 14750.59 217.45 67.75 14732.24 14732.24 481.00 32.65
38 214.00 66.35 14198.90 214.55 66.75 14321.21 14198.90 227.00 15.99
36 218.50 69.00 15076.50 217.80 68.00 14810.40 14810.40 411.00 27.75
7 216.00 67.80 14644.80 216.10 67.95 14684.00 14644.80 351.00 23.97
Sample 8
93 216.50 67.70 14657.05 216.50 67.45 14602.93 14602.93 422.00 28.90
89 217.30 67.80 14732.94 217.65 67.75 14745.79 14732.94 350.00 23.76
56 215.75 66.75 14401.31 215.45 66.75 14381.29 14381.29 381.00 26.49
57 217.20 68.90 14965.08 217.25 68.80 14946.80 14946.80 382.00 25.56
80 217.00 67.95 14745.15 217.35 68.55 14899.34 14745.15 373.00 25.30
94 216.25 67.45 14586.06 216.25 67.50 14596.88 14586.06 407.00 27.90
91 215.55 67.25 14495.74 215.95 68.00 14684.60 14495.74 430.00 29.66
52 214.95 67.00 14401.65 215.25 66.55 14324.89 14324.89 443.00 30.93
59 216.55 65.00 14075.75 216.65 66.25 14353.06 14075.75 435.00 30.90
50 214.35 66.00 14147.10 214.00 66.25 14177.50 14147.10 486.00 34.35
FACING BRICK – HEADER FACE Sample 1
70 98.50 67.30 6629.05 98.75 66.95 6611.31 6611.31 62.60 9.47
62 100.35 67.75 6798.71 99.50 67.00 6666.50 6666.50 62.20 9.33
45 67.25 100.10 6731.73 100.50 67.30 6763.65 6731.73 60.30 8.96
1 99.15 66.75 6618.26 100.25 67.25 6741.81 6618.26 60.80 9.19
16 99.55 66.85 6654.92 99.25 67.50 6699.38 6654.92 53.00 7.96
36 100.00 67.05 6705.00 100.95 67.00 6763.65 6705.00 56.30 8.40
64 100.65 67.30 6773.75 99.75 67.45 6728.14 6728.14 53.30 7.92
24 100.31 66.80 6700.71 100.20 66.50 6663.30 6679.68 61.20 9.16
5 99.80 66.65 6651.67 99.50 66.45 6611.78 6611.78 57.90 8.76
19 100.00 66.95 6695.00 99.95 67.10 6706.65 6695.00 61.00 9.11
Sample 2
17 101.10 68.95 6970.85 101.55 68.42 6948.05 6948.05 18.50 2.66
60 99.65 68.05 6781.18 99.91 68.00 6793.88 6781.18 27.00 3.98
16 100.85 67.25 6782.16 100.65 67.00 6743.55 6743.55 23.60 3.50
19 100.10 67.85 6791.79 100.15 67.77 6787.17 6787.17 26.70 3.93
71 100.00 68.75 6875.00 99.95 68.30 6826.59 6826.59 15.60 2.29
84 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.70 4.52
81 100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 24.30 3.61
99 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 20.80 3.05
85 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 27.90 4.27
86 98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 28.40 4.24
195
FACING BRICK – HEADER FACE Sample 3 Dimension 1 (mm) Area 1
mm2 Dimension 2 (mm) Brick
Identification
Length Width Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
45 98.15 69.10 6782.17 98.20 69.10 6785.62 6782.17 34.10 5.03
67 97.50 67.75 6605.63 97.35 67.75 6595.46 6595.46 28.00 4.25
58 101.00 67.75 6842.75 101.35 67.75 6866.46 6842.75 31.70 4.63
22 100.75 68.75 6926.56 99.30 68.75 6826.88 6826.88 14.90 2.18
26 99.50 68.80 6845.60 99.90 68.80 6873.12 6845.60 31.60 4.62
14 100.80 68.10 6864.48 100.95 68.42 6907.00 6864.48 47.30 6.89
56 99.00 66.20 6553.80 99.15 66.15 6558.77 6553.80 30.60 4.67
49 100.50 67.75 6808.88 100.65 67.70 6814.01 6808.14 31.80 4.67
2 97.65 67.60 6601.14 97.80 67.68 6619.10 6601.14 35.90 5.44
50 98.80 71.00 7014.80 98.90 70.95 7016.96 7014.80 17.60 2.51
Sample 4
24 100.50 67.25 6758.63 100.25 67.30 6746.83 6746.83 36.50 5.41
19 100.35 67.10 6733.49 100.20 67.25 6738.45 6733.49 36.10 5.36
20 101.25 67.00 6783.75 100.25 66.85 6701.71 6701.71 34.40 5.13
3 99.50 66.70 6636.65 99.25 66.60 6610.05 6610.05 41.00 6.20
7 98.80 66.50 6570.20 99.30 66.75 6628.28 6570.20 26.70 4.06
45 98.15 69.10 6782.17 98.20 69.10 6785.62 6782.17 34.10 5.03
67 97.50 67.75 6605.63 97.35 67.75 6595.46 6595.46 28.00 4.25
58 101.00 67.75 6842.75 101.35 67.75 6866.46 6842.75 31.70 4.63
22 100.75 68.75 6926.56 99.30 68.75 6826.88 6826.88 34.90 5.11
26 99.50 68.80 6845.60 99.90 68.80 6873.12 6845.60 31.60 4.62
Sample 5
83 99.70 67.30 6709.81 99.75 66.75 6658.31 6658.31 70.80 10.63
96 99.50 67.25 6691.38 99.00 67.25 6657.75 6657.75 37.30 5.60
79 100.25 67.00 6716.75 100.00 67.00 6700.00 6700.00 28.70 4.28
65 99.25 66.25 6575.31 98.55 66.60 6563.43 6563.43 47.10 7.18
71 100.75 67.00 6750.25 100.25 67.00 6716.75 6716.75 37.00 5.51
86 99.50 67.25 6691.38 99.80 67.60 6746.48 6691.38 76.40 11.42
74 98.80 66.75 6594.90 99.10 66.50 6590.15 6590.15 50.30 7.63
80 100.00 67.25 6725.00 100.25 66.65 6681.66 6681.66 44.50 6.66
91 100.80 67.00 6753.60 100.25 67.30 6746.83 6746.83 40.80 6.05
75 98.30 66.10 6497.63 97.75 66.25 6475.94 6475.94 49.00 7.57
Sample 6
1 98.55 67.95 6696.47 97.25 67.55 6569.24 6569.24 29.60 4.51
2 100.15 67.30 6740.10 100.25 67.85 6801.96 6740.10 37.90 5.62
3 100.10 68.20 6826.82 99.85 68.25 6814.76 6814.76 26.80 3.93
4 96.45 67.70 6529.67 98.55 68.05 6706.33 6529.67 30.80 4.72
5 100.22 67.55 6769.86 100.34 67.95 6818.10 6769.86 28.60 4.22
6 98.73 68.10 6723.51 99.96 68.55 6852.26 6723.51 33.60 5.00
7 99.55 69.10 6878.91 98.99 68.56 6786.75 6786.75 31.70 4.67
8 100.33 68.44 6866.59 98.95 67.99 6727.61 6727.61 21.20 3.15
9 97.10 69.99 6796.03 100.22 67.89 6803.94 6796.03 20.20 2.97
10 98.60 67.95 6699.87 99.00 68.30 6761.70 6699.87 46.00 6.87
196
FACING BRICK – HEADER FACE Sample 7 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
79 99.45 66.25 6588.56 99.95 66.90 6686.66 6588.56 36.00 5.46
80 99.50 66.30 6596.85 99.80 66.70 6596.85 6596.85 15.80 2.40
58 99.75 67.50 6733.13 99.75 67.40 6723.15 6723.15 21.30 3.17
73 99.75 66.70 6653.33 99.65 66.55 6631.71 6631.71 24.80 3.74
78 100.05 67.00 6703.35 100.45 66.85 6715.08 6703.35 37.23 5.55
66 98.25 67.00 6582.75 99.10 67.00 6639.70 6582.75 20.80 3.16
63 99.70 66.30 6610.11 99.45 66.25 6588.56 6588.56 28.00 4.25
53 98.50 66.55 6555.18 98.80 66.75 6594.90 6555.18 37.00 5.64
55 97.25 64.75 6296.94 99.25 66.55 6605.09 6296.94 4.70 0.75
69 99.25 67.00 6649.75 99.50 67.50 6716.25 6649.75 19.60 2.95
Sample 8
40 100.60 67.75 6815.65 100.25 68.00 6817.00 6815.65 57.00 8.36
45 97.75 66.85 6534.59 97.50 66.75 6508.13 6508.13 58.00 8.91
15 98.25 66.20 6504.15 98.50 66.10 6510.85 6504.15 36.00 5.53
35 99.00 67.00 6633.00 99.35 67.25 6681.29 6633.00 40.00 6.03
37 98.50 67.00 6599.50 97.00 66.10 6411.70 6411.70 47.00 7.33
1 100.50 66.75 6708.38 100.35 66.85 6708.40 6708.38 43.00 6.41
20 100.00 66.85 6685.00 100.55 66.85 6721.77 6685.00 41.00 6.13
8 99.65 66.90 6666.59 99.95 67.00 6696.65 6666.59 46.00 6.90
9 99.90 66.45 6638.36 99.35 66.50 6606.78 6606.78 32.00 4.84
24 99.70 66.75 6654.98 99.45 66.50 6613.43 6613.43 38.00 5.75
197
COMMON BRICKS – BED FACE Sample 1 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
- 216.10 99.25 21447.93 216.20 99.50 21511.90 21447.93 825.30 38.48 - 215.90 97.45 21039.46 215.50 97.45 21000.48 21000.48 829.30 39.49 - 217.50 100.05 21760.88 217.45 100.25 21799.36 21760.88 631.30 29.01 - 218.55 99.15 21669.23 219.05 99.95 21894.05 21669.23 866.30 39.98 - 217.85 98.95 21556.26 217.70 101.45 22085.67 21556.26 671.30 31.14 - 217.25 100.80 21898.80 217.25 101.20 21985.70 21898.80 791.30 36.13 - 217.95 99.65 21718.72 217.70 100.25 21824.43 21718.72 546.30 25.15 - 219.20 101.25 22194.00 219.25 100.40 22012.70 22012.70 866.30 39.35 - 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 613.30 27.79 - 219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 750.30 34.04
- 214.75 100 21475 215.7 99.75 21516.075 21475 850 39.58 - 214.25 100.75 21585.688 213.85 100.00 21385 21385 813 38.02 - 215.50 100.8 21722.4 215.55 100.75 21716.663 21716.66 783 36.06 - 214.55 100.25 21508.638 215.5 99.45 21431.475 21431.48 582 27.16 - 214.90 100.75 21651.175 215.10 100.70 21660.57 21651.18 855 39.49 - 216.55 100.75 21817.413 216.25 100.95 21830.438 21817.41 730 33.46 - 216.00 100.25 21654.00 216.45 101.00 21861.45 21654 543 25.08 - 216.25 100.5 21733.125 216.15 100.15 21647.423 21647.42 786 36.31 - 216.20 100.75 21782.15 216.25 101.45 21938.563 21782.15 745 34.20
- 215.70 100.4 21656.28 215.5 99.90 21528.45 21528.45 695 32.28
Sample 3
- 216.20 99.05 21414.61 216.20 99.35 21479.47 21414.61 830.00 38.76
- 215.90 97.00 20942.30 215.50 97.45 21000.48 20942.30 790.00 37.72
- 216.50 100.25 21704.13 217.45 100.30 21810.24 21704.13 636.00 29.30
- 217.75 99.25 21611.69 219.05 99.95 21894.05 21611.69 840.00 38.87
- 217.85 98.35 21425.55 217.70 101.25 22042.13 21425.55 567.00 26.46
- 217.35 100.20 21778.47 217.25 101.20 21985.70 21778.47 794.00 36.46
- 218.20 99.15 21634.53 217.70 100.25 21824.43 21634.53 543.00 25.10
- 218.75 101.05 22104.69 219.25 100.40 22012.70 22012.70 833.00 37.84
- 218.80 100.85 22065.98 219.45 101.20 22208.34 22065.98 614.00 27.83
- 219.00 100.65 22042.35 219.50 101.50 22279.25 22042.35 749.00 33.98
Sample 4
- 216.00 98.60 21297.60 216.00 98.60 21297.60 21297.60 607.90 28.54 - 219.50 101.10 22191.45 219.50 101.35 22246.33 22191.45 573.90 25.86 - 214.25 98.35 21071.49 214.20 98.40 21077.28 21071.49 473.90 22.49 - 219.60 101.95 22388.22 219.20 101.80 22314.56 22314.56 562.90 25.23
- 218.20 101.30 22103.66 218.45 101.30 22128.99 22103.66 501.90 22.71
- 214.35 97.00 20791.95 214.40 97.55 20914.72 20791.95 512.90 24.67
- 217.20 101.45 22034.94 217.25 100.25 21779.31 21779.31 462.90 21.25
- 219.80 101.65 22342.67 220.15 101.55 22356.23 22342.67 544.90 24.39
- 217.45 100.45 21842.85 217.34 100.15 21766.60 21766.60 437.80 20.11
- 215.95 99.95 21584.20 215.35 99.75 21481.16 21481.16 475.90 22.15
198
COMMON BRICKS – BED FACE Sample 5 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
- 219.25 98.00 21486.50 219.20 101.20 22183.04 21486.50 452.10 21.04
- 220.55 100.65 22198.36 220.85 100.95 22294.81 22198.36 604.10 27.21
- 218.20 99.65 21743.63 218.40 100.15 21872.76 21743.63 851.10 39.14
- 220.25 100.25 22080.06 220.75 101.00 22295.75 21798.44 849.20 38.96
- 221.25 102.95 22777.69 221.25 103.75 22954.69 22070.73 744.20 33.72
- 221.40 101.60 22479.00 221.60 101.95 22592.12 21594.65 711.20 32.93
- 218.95 100.75 22306.05 219.30 100.85 22116.41 22004.88 779.20 35.41
- 220.00 100.95 22103.00 219.80 100.95 22188.81 21668.89 687.20 31.71
- 218.20 100.70 22154.00 218.45 100.45 21943.30 21003.52 824.20 39.24
- 219.30 100.00 21820.00 219.25 100.25 21979.81 21338.00 857.20 40.17
Sample 6
- 216.35 97.60 21115.76 216.00 98.00 21168.00 21115.76 434.90 20.60
- 218.50 100.10 21871.85 218.75 101.25 22148.44 21871.85 573.90 26.24
- 214.20 98.25 21045.15 214.25 98.45 21092.91 21045.15 400.80 19.04
- 219.55 101.95 22383.12 219.25 100.80 22100.40 22100.40 560.00 25.34
- 217.20 100.30 21785.16 218.40 101.30 22123.92 21785.16 502.80 23.08
- 214.05 97.35 20837.77 214.25 97.75 20942.94 20837.77 512.90 24.61
- 216.20 101.25 21890.25 217.30 100.25 21784.33 21784.33 450.90 20.70
- 218.80 100.65 22022.22 219.50 101.45 22022.22 14999.66 542.90 36.19
- 218.45 101.45 22161.75 217.00 100.55 21819.35 21819.35 400.80 18.37
- 215.05 99.95 21494.25 215.35 99.65 21459.63 21459.63 465.90 21.71
Sample 7
- 216.35 97.60 21115.76 216.00 98.00 21168.00 21115.76 625.03 29.60
- 218.50 100.10 21871.85 218.75 101.25 22148.44 21871.85 828.94 37.90
- 214.20 98.25 21045.15 214.25 98.45 21092.91 21045.15 564.01 26.80
- 219.55 101.95 22383.12 219.25 100.80 22100.40 22100.40 680.69 30.80
- 217.20 100.30 21785.16 218.40 101.30 22123.92 21785.16 623.05 28.60
- 214.05 97.35 20837.77 214.25 97.75 20942.94 20837.77 700.15 33.60
- 216.20 101.25 21890.25 217.30 100.25 21784.33 21784.33 690.56 31.70
- 218.80 100.65 22022.22 219.50 101.45 22268.28 22022.22 466.87 21.20
- 218.45 101.45 22161.75 217.00 100.55 21819.35 21819.35 440.75 20.20
- 215.05 99.95 21494.25 215.35 99.65 21459.63 21459.63 987.14 46.00
Sample 8
- 214.55 97.75 20972.26 215.00 98.25 21123.75 20972.26 872.50 41.60
- 213.45 96.80 20661.96 213.30 96.80 20647.44 20647.44 883.60 42.79
- 213.45 96.80 20661.96 213.30 97.45 20786.09 20661.96 751.60 36.38
- 216.00 98.70 21319.20 215.50 98.60 21248.30 21248.30 815.50 38.38
- 214.85 98.50 21162.73 215.00 98.50 21177.50 21162.73 876.60 41.42
- 215.00 98.00 21070.00 214.95 97.50 20957.63 20957.63 1017.60 48.56
- 212.25 98.00 20800.50 212.25 97.75 20747.44 20747.44 1032.60 49.77
- 217.00 99.75 21645.75 217.00 99.00 21483.00 21483.00 849.60 39.55
- 214.00 98.00 20972.00 214.95 97.75 21011.36 20972.00 913.60 43.56
- 212.45 96.25 20448.31 212.25 96.00 20376.00 20376.00 832.60 40.86
199
COMMON BRICKS – BED FACE Sample 9 Dimension 1 (mm) Dimension 2 (mm) Brick
Identification Length Width
Area 1 mm2
Length Width
Area 2 mm2
Smaller area mm2
Max load Kn
Compressive strength N/mm2
- 216.36 96.75 20932.83 216.25 98.25 21246.56 20932.83 713.50 34.09
- 213.25 96.80 20642.60 213.30 96.80 20647.44 20642.60 793.60 38.44
- 210.30 97.80 20567.34 210.30 97.45 20493.74 20493.74 751.60 36.67
- 215.45 98.70 21264.92 215.50 98.60 21248.30 21248.30 758.50 35.70
- 214.85 98.50 21162.73 215.00 98.50 21177.50 21162.73 856.60 40.48
- 212.55 98.30 20893.67 214.95 97.50 20957.63 20893.67 988.60 47.32
- 212.25 98.00 20800.50 212.25 97.75 20747.44 20747.44 1015.60 48.95
- 217.00 99.75 21645.75 217.00 99.00 21483.00 21483.00 792.60 36.89
- 214.00 98.00 20972.00 214.95 97.75 21011.36 20972.00 953.60 45.47
- 212.45 96.25 20448.31 212.25 96.00 20376.00 20376.00 832.60 40.86
Sample 10
- 215.50 97.75 21065.13 215.75 97.55 21046.41 21046.41 1081.50 51.39
- 215.25 98.95 21298.99 214.90 98.00 21060.20 21060.20 1221.60 58.01
- 214.00 97.45 20854.30 214.10 97.50 20874.75 20854.30 1077.60 51.67
- 213.85 97.70 20893.15 214.15 97.95 20975.99 20893.15 1027.50 49.18
- 215.00 98.00 21070.00 215.00 98.00 21070.00 21070.00 1061.60 50.38
- 214.50 98.00 21021.00 214.35 98.25 21059.89 21021.00 1032.60 49.12
- 214.00 98.50 21079.00 214.65 97.25 20874.71 20874.71 980.60 46.98
- 214.70 97.75 20986.93 214.65 97.25 20874.71 20874.71 974.60 46.69
- 211.10 96.25 20318.38 211.25 96.35 20353.94 20318.38 958.60 47.18
- 215.40 98.35 21184.59 215.25 98.10 21116.03 21116.03 722.60 34.22
Sample 11
- 216.00 98.00 21168.00 216.25 98.25 21246.56 21168.00 813.80 38.44
- 215.90 97.35 21017.87 215.40 97.60 21023.04 21017.87 926.60 44.09
- 213.45 98.00 20918.10 213.75 99.15 21193.31 20918.10 928.00 44.36
- 214.95 97.60 20979.12 215.25 97.25 20933.06 20933.06 797.60 38.10
- 212.75 96.00 20424.00 213.00 96.00 20448.00 20424.00 1002.60 49.09
- 213.80 98.75 21112.75 214.25 98.00 20996.50 20996.50 948.60 45.18
- 212.00 96.65 20489.80 216.65 97.00 21015.05 20489.80 1001.60 48.88
- 214.45 98.35 21091.16 214.55 98.25 21079.54 21079.54 833.60 39.55
- 212.00 94.75 20087.00 212.20 95.75 20318.15 20087.00 967.60 48.17
- 216.00 97.25 21006.00 215.75 97.00 20927.75 20927.75 691.60 33.05
Sample 12
- 213.00 96.95 20650.35 213.50 97.75 20869.63 20650.35 1003.50 48.59
- 215.75 99.65 21499.49 215.45 99.30 21394.19 21394.19 740.60 34.62
- 212.25 96.95 20577.64 212.00 97.25 20617.00 20577.64 914.60 44.45
- 212.95 97.25 20709.39 213.00 97.25 20714.25 29709.39 765.50 25.77
- 217.40 98.75 21468.25 217.95 98.50 21468.08 21468.08 899.60 41.90
- 212.60 97.35 20696.61 212.55 96.90 20596.10 20596.10 1032.60 50.14
- 214.25 98.75 21157.19 214.20 98.75 21152.25 21152.25 952.60 45.04
- 215.10 99.00 21294.90 215.35 99.25 21373.49 21294.90 930.60 43.70
- 214.40 97.75 20957.60 214.90 97.30 20909.77 20909.77 870.60 41.64
- 215.40 98.35 21184.59 215.25 98.10 21116.03 21116.03 722.60 34.22
B
STATISTICAL TABLES
201
Table B1: 5 per cent points of the F-distribution (Adapted from Loveday, 1975)
1ν = 1 2 3 4 5 6 7 8 10 12 24 ∞ 2ν = 1 161.4 199.5 215.7 224.6 230.2 234.0 236.8 238.9 241.9 243.9 249.0 254.3
2 18.5 19.0 19.2 19.2 19.3 19.3 19.4 19.4 19.4 19.4 19.5 19.5 3 10.13 9.55 9.28 9.12 9.01 8.94 8.89 8.85 8.79 8.74 8.64 8.53 4 7.71 6.94 6.59 6.39 6.26 6.16 6.09 6.04 5.96 5.91 5.77 5.63
5 6.61 5.79 5.41 5.19 5.05 4.95 4.88 4.82 4.74 4.68 4.53 4.36 6 5.99 5.14 4.76 4.53 4.39 4.28 4.21 4.15 4.06 4.00 3.84 3.67 7 5.59 4.74 4.35 4.12 3.97 3.87 3.79 3.73 3.64 3.57 3.41 3.23 8 5.32 4.46 4.07 3.84 3.69 3.58 3.50 3.44 3.35 3.28 3.12 2.93 9 5.12 4.26 3.86 3.63 3.48 3.37 3.29 3.23 3.14 3.07 2.90 2.71
10 4.96 4.10 3.71 3.48 3.33 3.22 3.14 3.07 2.98 2.p1 2.74 2.54 11 4.84 3.98 3.59 3.36 3,20 3.09 3.01 2.95 2.85 2.79 2.61 2.40 12 4.75 3.89 3.49 3.26 3.11 3.00 2.91 2.85 2.75 2.69 2.51 2.30 13 4.67 3.81 3.41 3.18 3.03 2.92 2.83 2.77 2.67 2.60 2.42 2.21 14 4.60 3.74 3.34 3.11 2.96 2.85 2.76 2.70 2.60 2.53 2.35 2.13
15 4.54 3.68 3.29 3.06 2.90 2.79 2.71 2.64 2.54 2.48 2.29 2.07 16 4.49 3.63 3,.24 3.01 2.85 2.74 2.66 2.59 2.49 2.42 2.24 2.01 17 4.45 3.59 3.20 2.96 2.81 2.70 2.61 2.55 2.45 2.38 2.19 1.96 18 4.41 3.55 3.16 2.93 2.77 2.66 2.58 2.51 2.41 2.34 2.15 1.92 19 4.38 3.52 3.13 2.90 2.74 2.63 2.54 2.48 2.38 2.31 2.11 1.88
20 4.35 3.49 3.10 2.87 2.71 2.60 2.51 2.45 2.35 2.28 2.08 1.84 21 4.32 3.47 3.07 2.84 2.68 2.57 2.49 2.42 2.32 2.25 2.05 1.81 22 4.30 3.44 3.05 2.82 2.66 2.55 2.46 2.40 2.30 2.23 2.03 1.78 23 4.28 3.42 3.03 2.80 2.64 2.53 2.44 2.37 2.27 2.20 2.00 1.76 24 4.26 3.40 3.01 2.78 2.62 2.51 2.42 2.36 2.25 2.18 1.98 1.73
25 4.24 3.39 2.99 2.76 2.60 2.49 2.40 2.34 2.24 2.16 1.96 1.71 26 4.23 3.37 2.98 2.74 2.59 2.47 2.39 2.32 2.22 2.15 1.95 1.69 27 4.21 3.35 2.96 2.73 2.57 2.46 2.37 2.31 2.20 2.13 1.93 1.67 28 4.20 3.34 2.95 2.71 2.56 2.45 2.36 2.29 2.19 2.12 1.91 1.65 29 4.18 3.33 2.93 2.70 2.55 2.43 2.35 2.28 2.18 2.10 1.90 1.64
30 4.17 3.32 2.92 2.69 2.53 2.42 2.33 2.27 2.16 2.09 1.89 1.62 32 4.15 3.29 2.90 2.67 2.51 2.40 2.31 2.24 2.14 2.07 1.86 1.59 34 4.13 3.28 2.88 2.65 2.49 2.38 2.29 2.23 2.12 2.05 1.84 1.57 36 4.11 3.26 2.87 2.63 2.48 2.36 2.28 2.21 2.11 2.03 1.82 1.55 38 4.10 3.24 2.85 2.62 2.46 2.35 2.26 2.19 2.09 2.02 1.81 1.53
40 4.08 3.23 2.84 2.61 2.45 2.34 2.25 2.18 2.08 2.00 1.79 1.51 60 4.00 3.15 2.76 2.53 2.37 2.25 2.17 2.10 1.99 1.92 1.70 1.39
120 3.92 3.07 2.68 2.45 2.29 2.18 2.09 2.02 1.91 1.83 1.61 1.25 ∞ 3.84 3.00 2.60 2.37 2.21 2.10 2.01 1.94 1.83 1.75 1.52 1.00
202
Table B2: Distribution of tc (Adapted from Kennedy and Neville, 1985)
Probability, α Degrees of
freedom (df) 0.10 0.05 0.01 0.001 1 6.314 12.706 63.657 636.619 2 2.920 4.303 9.925 31.598 3 2.353 3.182 5.841 12.941 4 2.12 2.776 4.604 8.610 5 2.015 2.571 4.032 6.859 6 1.943 2.447 3.707 5.959 7 1.895 2.365 3.499 5.405 8 1.860 2.306 3.355 5.041 9 1.833 2.262 3.250 4.781
10 1.812 2.228 3.169 4.587 11 1.796 2.201 3.106 4.437 12 1.782 2.179 3.055 4.318 13 1.771 2.160 3.012 4.221 14 1.761 2.145 2.977 4.140 15 1.753 2.131 2.947 4.073 16 1.746 2.120 2.921 4.015 17 1.740 2.110 2.898 3.965 18 1.734 2.101 2.878 3.922 19 1.729 2.093 2.861 3.883 20 1.725 2.086 2.845 3.850 21 1.721 2.080 2.831 3.819 22 1.717 2.074 2.819 3.792 23 1.714 2.069 2.807 3.767 24 1.711 2.064 2.797 3.745 25 1.708 2.060 2.787 3.725 26 1.706 2.056 2.779 3.707 27 1.703 2.052 2.771 3.690 28 1.701 2.048 2.763 3.674 29 1.699 2.045 2.756 3.659 30 1.697 2.042 2.750 3.646 40 1.684 2.021 2.704 3.551 60 1.671 2.000 2.660 3.460
120 1.658 1.980 2.617 3.373 ∞ 1.645 1.960 2.576 3.290
203
Table B3: Range coefficient d (Adapted from Kennedy and Neville, 1985)
Number of observations,
n
Coefficient, d
Number of observations,
n
Coefficient,
d 2 0.8862 14 0.2935 3 0.5908 15 0.2880 4 0.4857 16 0.2831 5 0.4299 17 0.2787 6 0.3945 18 0.2747 7 0.3698 19 0.2711 8 0.3512 20 0.2677 9 0.3367 24 0.2567 10 0.3249 50 0.2223 11 0.3152 100 0.1994 12 0.3069 1000 0.1543 13 0.2998
Table B.4: Factors for control lines for mean and range charts values (BS 2846:1991)
For mean For range
Warning line
Action line
Lower action
line
Lower warning
line
Upper warning
line
Upper action
line
Number in subgroup
n
'0.025 A '
0.001A '0.999D '
0.975D '0.025D '
0.001D 2 1.229 1.937 0.00 0.04 2.81 4.12 3 0.668 1.054 0.04 0.18 2.17 2.99 4 0.476 0.750 0.10 0.29 1.93 2.58 5 0.377 0.594 0.16 0.37 1.81 2.36 6 0.316 0.498 0.21 0.42 1.72 2.22 7 0.274 0.432 0.26 0.46 1.66 2.12 8 0.244 0.384 0.29 0.5 1.62 2.04 9 0.220 0.347 0.32 0.52 1.58 1.99 10 0.202 0.317 0.35 0.54 1.55 1.94 11 0.186 0.294 0.38 0.56 1.53 1.90