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CHAPTER 1
INTRODUCTON
1.1 GENERAL
Concrete is by far the most widely used construction material today. Concrete
has attained the status of a major building material in all branches of modern construction
because of following reasons.
It is possible to control the properties of cement concrete with in a wide range by using
appropriate ingredients and by applying special processing techniques- mechanical, chemical
and physical. It is possible to mechanize completely its preparation and placing process. It
possess adequate plasticity for mechanical working.
It is difficult to point out another material of constructions which is as versatile as concrete.
Concrete is by far the best material of choice where strength, durability, permanence,
impermeability, fire resistance and abrasion resistance are required.
In present world, inflation is one of the main problems faced by every country. It has become
essential to lower the construction cost without much compromise as far as strength and
durability of the structure is concerned. The lowering of cost can be brought about in number
of ways. Among all the methods available the most optimum at our disposal is the use of
waste material as substitute.
The basic requirement of all mankind is shelter. Hence the shelter is based on the building
construction in which the cement concrete is an essential requirement. The cement concrete
is a well-known building material and has occupied an indispensable place in construction
work.
From the materials of varying properties, to make concrete of stipulated qualities and
intimate knowledge of the interaction of various ingredients, that go into the making of
concrete is required to be known, both in plastic condition and in the harden condition.
The strength of concrete depends upon the components such as aggregate, quality of
cement, water-cement ratio, workability, normal consistency of mix, proportion and age of
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concrete .New building materials are used to accelerate the construction work, in which the
mixture plays an important role in characteristics of concrete .
The growth in various types of industries together with population growth has
resulted in the enormous increase in the production of various types of industrial waste
materials such as rice husk ash, foundry sand, blast furnace slag, fly ash, steel slag, scrap
tires, waste plastic, broken glass, etc.
1.2 STATEMENT OF PROBLEM
A comparative evaluation of strength characteristics of control concrete of grade M20
and RHA concrete produced by replacing cement by raw RHA in different percentage (
0,5,10, 15, and 20 % ).
1.3 OBJECTIVESOF THE STUDY
The primary aim of experimental work is to study the properties of rice husk ash.
Preparation of mix design Replacement of cement with RHA as different proportions with
cement.
Effect of rice husk ash on workability
Effect on compressive strength of concrete
Effect on split tensile strength of concrete
Todetermine the optimum dosage of the rice husk to be added to the concrete mix.
Comparison of result of different tests with varying proportion of RHA.
1.4 SCOPE OF THE STUDY
The increasing demand for producing durable materials is the outcome of fast
polluting environment. Supplementary cementations materials prove to be effective to meet
most of the requirements of the durable concrete. Rice husk ash is found to be greater to
other supplementary materials like silica fume and fly ash.
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1.5 RICE HUSK ASH (RHA)
1.5.1 HISTORICAL BACKGROUND
Rice plant is one of the plants that absorbs silica from the soil and assimilates it into
its structure during the growth. Rice husk is the outer covering of the grain of rice plant with
a high concentration of silica, generally more than 80-85%. It is responsible for
approximately 30% of the gross weight of a rice kernel and normally contains 80% of
organic and 20% of inorganic substances. Rice husk is produced in millions of tons per year
as a waste material in agricultural and industrial processes. It can contribute about 20% of its
weight to Rice Husk Ash (RHA) after incineration. RHA is a highly pozzolanic material. The
non-crystalline silica and high specific surface area of the RHA are responsible for its high
pozzolanic reactivity. RHA has been used in lime pozzolanic mixes and could be a suitable
partly replacement for Portland cement. RHA concrete is like fly ash/slag concrete with
regard to its strength development but with a higher pozzolanic activity it helps the
pozzolanic reactions occur at early ages rather than later as is the case with other replacement
cementing materials.
Rice husk ash (RHA) is a by-product from the burning of rice husk. Rice husk is
extremely prevalent in East and South-East Asia because of the rice production in this area.
The rich land and tropical climate make for perfect conditions to cultivate rice and is taken
advantage by these Asian countries. The husk of the rice is removed in the farming process
before it is sold and consumed. It has been found beneficial to burn this rice husk in kilns to
make various things. The rice husk ash is then used as a substitute or admixture in cement.
Therefore the entire rice product is used in an efficient and environmentally friendly
approach.
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Raw Rice Husk Burnt RHA After sieving
Fig 1.1 RICE HUSK ASH
1.5.2 BURNING PROCESS
The rice husk ash is a highly siliceous material that can be used as an admixture in
concrete if the rice husk is burnt in a specific manner. The characteristics of the ash are
dependent on the components, temperature and time of burning. During the burning process,
the carbon content is burnt off and all that remains is the silica content. The silica must be
kept at a non-crystalline state in order to produce an ash with high pozzalanic activity. The
high pozzalanic behaviour is a necessity if you intend to use it as a substitute or admixture in
concrete. It has been tested and found that the ideal temperature for producing such results is
between 600 °C and 700 °C. If the rice husk is burnt at too high temperature or for too long
the silica content will become a crystalline structure. If the rice husk is burnt at too low
temperature or for too short period of time the rice husk ash will contain too large an amount
of un-burnt carbon.
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1.6 PROPERTIES:
1.6.1 SPECIFICATION OF RICE HUSK ASH:
Table1.1SpecificationsofRiceHuskAsh
SL No. Parameter Values
1 SiO2-Silica 85% minimum
2 Humidity 2% maximum
3 Mean Particle Size 25µ
4 Colour Grey
5 Loss on Ignition at 800
0
C 4% maximum
1.6.2 PHYSICAL PROPERTIES OF RICE HUSK ASH:
Table 1.2 Physical Properties of Rice HuskAsh
Sl No. Parameter Value
1 Physical State Solid-NonHazardous
2 Appearance Very fine powder
3 Particle Size 25 microns-mean
4 Colour Grey
5 Odour Odourless
6 Specific Gravity 2.3
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1.6.3 CHEMICAL PROPERTIES OF RICE HUSK ASH:
Table 1.3: Chemical Composition of RHA
Constituents % Composition
Fe2O3 1.38
SiO2 90.20
Al2O3 0.85
CaO 1.18
MgO 1.21
Loss on ignition 3.95
1.7 REACTION MECHANISM
1.7.1 Pozzolanic reaction
A pozzolanic reaction occurs when a siliceous or aluminous material get in touch
with calcium hydroxide in the presence of humidity to form compounds exhibiting
cementitious properties. The calcium silicate hydrate (C-S-H) and calcium hydroxide
(Ca(OH)2, or CH) are released within the hydration of two main components of cement
namely tricalcium silicate (C3S) and dicalcium silicate (C2S) where C, S represent CaO and
SiO2. Hydration of C3S, C2S also C3A and C4AF (A and F symbolize Al2O3 and Fe2O3)
respectively, is important. Upon wetting, the following reactions occur:
2(3CaO.SiO2) + 6H20 3CaO.2SiO2.3H20 + 3Ca (OH) 2 …………… (1)
2(2CaO.SiO2) + 4H20 3CaO.2SiO2.3H20 + Ca (OH) 2 …………… (2)
3CaO.Al203 + 3H20 + 3CASO4
3CaO.Al203. 3CaSO4. 3H20 …………… (3)
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4CaO.A1203.Fe203 + 10H20 + 2Ca (OH) 2
6CaO Al203. Fe203. 12 …………… (4)
The C-S-H gel generated by the hydration of C3S and C2S in equations (1) and (2) is
the main strengthening constituent. Calcium hydroxide and Ettringite (3CaO.3CaSO4.31H20,
equation 3) that are crystalline hydration products are randomly distributed and form the
frame of the gel-like products. Hydration of C4AF (equation 4), consumes calcium hydroxide
and generates gel-like products. Excess calcium hydroxide can be detrimental to concrete
strength, due to tending the crystalline growth in one direction. It is known that by adding
pozzolanic material to mortar or concrete mix, the pozzolanic reaction will only start when
CH is released and pozzolan/CH interaction exist. In the pozzolan-lime reaction, OH- and Ca
2+ react with the SiO2 or Al203-SiO 2 framework to form calcium silicate hydrate (C-S-H),
calcium aluminate hydrate (C-A-H), and calcium aluminate ferrite hydrate:
Tobermorite gel:
SiO2 + Ca (OH)2 + H20 CaO.SiO2.H20 ……… (5)
Calcium aluminate hydrate:
Ca (OH)2 + H20 + Al203 aO.A1203.Ca(OH)2.H2O ……. (6)
Calcium aluminate ferrite hydrate:
Ca (OH)2+ Fe203 + A1203 + H20
Ca(OH)2.A1203.Fe203.H20 ……… (7)
The crystallized compound of C-S-H and C-A-H, which are called cement gel,
hardened with age to form a continuous binding matrix with a large surface area and are
components responsible for the development of strength in the cement paste. Pozzolan-lime
reactions are slow, generally starting after one or more weeks. The behavior of the delay in
pozzolanic reaction will result in more permeable concrete at early ages and gradually
becomes denser than plain concrete with time. This behavior is due to two reasons: Firstly,
pozzolan particles become the precipitation sites for the early hydration C-S-H and CH that
hinders pozzolanic reaction. Secondly, the strong dependency of the breaking down of glass
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phase on the alkalinity of the pore water which could only attain the high pH after some days
of hydration. Pozzolan can partially replace cement in mortar or concrete mix without
affecting strength development.
1.7.2 Pozzolanic reaction of RHA
Data from reaction results between RHA and CH indicates that the amount of CH by
30% RHA in cement paste begins to decrease after 3 days, and by 91 days it reaches nearly
zero, while in the control paste, it is considerably enlarged with hydration time. The addition
of pozzolan decreases the formed CH by the pozzolanic reaction to produce more C-S-H gel
that can improve the strength and durability of concrete. Amorphous silica that is found in
some pozzolanic materials reacts with lime more eagerly than those of crystalline form. The
most essential asset of RHA that identifies pozzolanic activity is the amorphous phase
substance. The RHA is an approximately 85% to 95% by weight of amorphous silica.
As a consequence of this extremely reactive pozzolanic substance appropriate for use
in lime-pozzolan mixes and for Portland cement substitution. The reactivity of RHA
associated to lime depends on a combination of two factors: namely the non-crystalline silica
content and its specific surface. Cement replacement by rice husk ash accelerates the early
hydration of C3S.
The increase in the early hydration ratio of C3S is attributed to the high
specific surface area of the rice husk ash. This phenomenon specially takes place with fine
particles of RHA. Although the small particles of pozzolans are less reactive than Portland
cements, they produce a large number of nucleation sites for the precipitation of the
hydration products by dispersing in cement pastes. Consequently, this mechanism creates the
more homogenous and denser paste as for the distribution of the finer pores due to the
pozzolanic reactions among the amorphous silica of the mineral addition and the CH. Mehta
(1987) reported that the finer particles of RHA speed up the reactions and form smaller CH
crystals. (2001) have exposed that pozzolanic reaction can be characterized by the Jander
diffusion equation based on Fick's parabolic law of diffusion assuming the interface is a
contracting sphere. The Jander equation for three dimensional diffusion in a sphere is (1- (1 –
x) 1/3)2=(D/r2)kt where x is the fraction of the sphere that has reacted, r is initial radius of
the starting sphere, and k is the diffusion constant.
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1.8 ADVANTAGES OF USING RICE HUSK ASH IN
CONCRETE
The use of RHA in concrete has been associated with the following essential assets:
Increased compressive and flexural strengths.
Reduced permeability.
Increased resistance to chemical attack.
Increased durability.
Reduced effects of alkali-silica reactivity.
Reduced shrinkage due to particle packing, making concrete denser.
Enhanced workability of concrete.
Reduced heat gain through the walls of buildings.
Reduced amount of super plasticizer.
Reduced potential for efflorescence due to reduced calcium hydroxides
1.9 APPLICATIONS
Portland cement manufacturing.
Road base / Sub base.
Landfill cover or hydraulic barriers.
Parking lot construction.
High quality RHA can be used as a super pozzolanic additive for HSC.
Low quality RHA can be used as filler for concrete
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CHAPTER 2
LITERATURE REVIEW
Many researchers have studied the effect of replacement of Cement by Rice Husk
Ash which increases the mechanical and durability properties of concrete.
2.1 “Effect of Rice Husk Ash on Properties of High Strength
Concrete”byDAO VAN DONG, PHAM DUY AND NGUYEN NGOCLAN
(2008)
Rice Husk is an abundant waste generated from agricultural product in Vietnam. This
is a potential source to produce RHA for construction applications in Vietnam. Low quality
RHA can be used as filler for concrete. The acceptable content is 15% to replace for cement
with an acceptance of reduction in compressive strength. High quality RHA can be used as a
super pozzolanic additive for HSC. HSC used 15% RHA to replace for cement obtains
substantial improvements in properties, especially, compressive strength, and water and
chloride resistance. Investigations in manufacturing high quality RHA in Vietnam are
necessary.
The replacement of RHA for cement results in decreases in compressive strength
compared to the control samples. At age of 28 days there is no big difference between
compressive strength of 10% and 15% RHA samples. However, the use 20% RHA leads to a
significant reduction of compressive strength. Additionally the rate of development of
compressive strength of the RHA concrete samples tends to decrease the age of curing. These
could be due to that RHA does not act as a cement replacement because of its coarse particle
size and low reactivity. From these data it is designed that 15% RHA is an acceptable
percentage of RHA as cement replacement.
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2.2 “Experimental Study on Strength of Concrete by Using Artificial
Fibers with Rice Husk Ash” by SANDESH D. DESHMUKH,
PRAVINV.DOMKE, SATISH D. KENE, R.S.DEOTALE(2008)
Husk ash Properties studied include workability of fresh concrete, compressive
strength, flexural tensile strength, splitting This paper reports on a comprehensive study on
the properties of concrete containing rice tensile strength, modulus of elasticity for hardened
concrete. Rice husk ash content was use from 0% to 20% in the interval of 2.5% in weight
basis. It was found that the strength of concrete reduces after further addition of 12.5% of
rice husk ash. The laboratory results Shown that steel fiber addition either into Portland
cement concrete or rice husk ash concrete, improve the tensile strength properties. However,
it reduced workability. Although rice husk ash replacement reduces strength properties. The
performed experiments show that the behavior of rice husk ash concrete is not similar to that
of Portland cement concrete when rice husk ash is added.
Compressive strength of concrete mixtures was measured at the ages of 7, 14, 28 and 90 days
and shown in Table 2.1. There was an increase up to 10% and reduction up to 6%
compressive strength of cube concrete specimens produced. This may be due to the physical
difficulties inproviding a homogeneous mix within the concrete causing rise or drop in
thecompressive strength as compared to the plainconcrete. The addition of rice husk ash to
the concretemixture did not improve compressive strength of 7days and 14 days of curing
specimen, but after28days and 90 days only small increase (up to 10%) in compressive
strength was observed. The presence of rice husk ash, whencompared with plain concrete,
decreased the averagecompressive strength by 10% and 14% for 15% and30% rice husk ash
replacement ratio, respectively.If the amount of mixing water was reduced on the basis of
equal Vee-Bee workability, it appears that thereduction in compressive strength due to
addition ofrice husk ash can be recovered significantly.
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Table 2.1: Compressive Strength test
Fig.2.2 Effect of RHA on compressive strength
No RHA(%)
Byweight
7Days
(N/mm2)
14 Days
(N/mm2)
28 Days
(N/mm2)
90 Days
(N/mm2)
A1 0 23.56 24.89 40.00 42.22
A2 2.5 22.67 23.02 36.89 40.00
A3 5.0 22.22 22.89 36.44 37.78
A4 7.5 21.56 22.67 35.56 36.44
A5 10.0 21.33 22.22 34.22 34.67
A6 12.5 20.89 21.11 33.33 33.78
A7 15.0 16.44 16.89 17.78 18.22
A8 17.5 15.56 16.00 16.44 16.89
A9 20 15.11 15.56 15.56 16.44
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2.3 “The Possibility of Adding the Rice Husk Ash (RHA) to the Concrete”
by MAURO M. TASHIMA, CARLOS A. R. DA SILVA, JORGE L.
AKASAKI , MICHELE BENITI BARBOSA.
This paper evaluates how different contents of rice husk ash (RHA) added to concrete
may influence its physical and mechanical properties. Samples were tested, with 5% & 10%
of RHA, replacing in mass the cement. Properties like simple compressive strength, split
tensile strength were evaluated. The results were compared to control sample and the
viability of adding RHA to concrete was verified.
The compressive strength is shown in Table 2.2. The addition of RHA causes an
increment in the compressive strength due to the capacity of the pozzolana, of fixing the
calcium hydroxide, generated during the reactions of hydrate of cement. All the replacement
degrees of RHA increased the compressive strength. For a 5% of RHA, 25% of increment is
verified when compared with mixtures.
The resultsof splittingtensilestrengthare shown in Table 2.3. All the replacement degrees
of RHA researched, achieve similar results in split tensile strength. According to the results,
may be realized that there is no interference of adding RHA in the split tensile strength.
The use of RHA in civil construction. An increment of 25% was obtained when was
added 5% of RHA. Moreover, a reducing on waste Portland cement was verified, obtaining
the same resistance of control sample. According to the results of split tensile test, all the
replacement degrees of RHA researched, achieve similar results. Then, maybe realized that
there is no interference of adding RHA in the split tensile strength. All the samples studied
have a similar results in elasticity module. A decreasing in the module is realized when the
levels of RHA are increasing.
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2.4 “Use of Ultrafine Rice Husk Ash with high-carbon content as pozzolan
in high performance concrete” by GUILHERMECHAGASCORDEIRO,
ROMILDO DIAS TOLEDO FILHO, EDUARDO DE MORAESREGO
FAIRBAIRN (2008).
Rice husk ash (RHA) has been generated in large quantities in rice producing
countries. This by-product can contain non-crystalline silica and thus has a high potential to
be used as cement replacement in mortar and concrete. However, as the RHA produced by
uncontrolled burning conditions usually contains high-carbon content in its composition, the
pozzolanic activity of the ash and the rheology of mortar or concrete can be adversely
affected. In this paper the influence of different grinding times in a vibratory mill, operating
in dry open-circuit, on the particle size distribution, in order to improve RHA’s performance.
In addition, four high-performance concretes were produced with 0%, 10%, 15%, and 20%
of the cement (by mass) replaced by ultrafine RHA. For these mixtures, rheological,
mechanical and durability tests were performed.
For all levels of cement replacement, especially for the 20%, the ultra-fine RHA
concretes achieved superior performance in the mechanical and durability tests compared
with the reference mixture. The workability of the concrete, however, was reduced with the
increase of cement replacement by RHA.
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2.5 “Study on Properties of Rice Husk Ash and Its Use as Cement
Replacement Material” byGHASSAN ABOOD HABEEB, HILMI BIN
MAHMUD (2009).
This paper investigates the properties of rice husk ash (RHA) produced by using a
ferro-cement furnace. The effect of grinding on the particle size and the surface area was first
investigated, and then the XRD analysis was conducted to verify the presence of amorphous
silica in the ash. Furthermore, the effect of RHA average particle size and percentage on
concrete workability, fresh density, superplasticizer (SP) content and the compressive
strength were also investigated. Although grinding RHA would reduce its average particle
size (APS), it was not the main factor controlling the surface area and it is thus resulted from
RHA’s multilayered, angular and microporous surface. Incorporation of RHA in concrete
increased water demand. RHA concrete gave excellent improvement in strength for 10%
replacement (30.8% increment compared to the control mix), and up to 20% of cement could
be valuably replaced with RHA without adversely affecting the strength. Increasing RHA
fineness enhanced the strength of blended concrete compared to coarser RHA and control
OPC mixtures.
In terms of the replacement level, the 5% replacement level achieved slightly lower
values of compressive strength at early ages for up to 7 days except for the mixture where the
compressive strength was higher due to the increased reactivity and the filler effect of RHA.
Based on that, it can be noticed that the amount of RHA present when 5% replacement used
is not adequate to enhance the strength significantly.
The strength increased with RHA for up to 10% which resulted in achieving the
maximum value. For example, 10% mixture resulted in 30.8% increment compared to the
OPC control mix tested at 28 days age, that is due to the pozzolanic reaction of the available
silica from the RHA and the amount of C-H available from the hydration process and also
due to the microfiller effect when fine RHA is used.
The strength values when RHA was replaced by 15% were found to be similar to 5%
replacement except that at the age of 7 days, the strength was higher than the control for all
RHA mixtures, in this case, the amount of silica available in the hydrated blended cement
matrix is probably too high and the amount of the produced C-H is most likely insufficient to
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react with all the available silica and as a result of that, some amount of silica was left
without any chemical reaction.
When 20% of OPC was replaced for RHA, the strength of concrete achieved
equivalent values to the OPC control mixture. Increasing the replacement to a level above
20% was avoided in this study due to the fact that the increased water demand would lead to
SP content higher than the manufacturer recommendations (maximum of 2% by weight of
the cementitious materials) which can give an adverse effect on the produced concrete by
acting as a retarder and increasing cost. Furthermore, the strength would decrease to a value
that is lower than the control. The released amount of C-H due to the hydration process is not
sufficient to react with all the available silica from the addition of RHA and thus, the silica
will act as inert material and will not contribute to the strength the RHA used in this study is
efficient as a pozzolanic material; it is rich in amorphous silica (88.32%). The loss on
ignition was relatively high (5.81%). Increasing RHA fineness increases its reactivity.
Grinding RHA to finer APS has slightly increased its specific surface area, thus, RHA APS is
not the main factor controlling its surface area. The dosage of superplasticizer had to be
increased along with RHA fineness and content to maintain the desired workability. The
compressive strength of the blended concrete with 10% RHA has been increased
significantly, and for up to 20% replacement could be valuably replaced by cement without
adversely affecting the strength. Increasing RHA fineness enhances the strength of blended
concrete.
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CHAPTER 3
MATERIALS AND METHODOLOGY
3.1 MATERIALES USED
3.1.1 CEMENT
In this experiment 43 grade ordinary Portland cement (OPC) with brand name ultra
tech was used for all concrete mixes. The cement used was fresh and without any lumps. The
testing of cement was done as per IS:8112-1989. The specific gravity of cement was found to
be 3.15.The physical properties of cement used are as given in table.
Table 3.1 physical properties of cement
Particulars Experimental result As per standard
1.Fineness 6% 10%
2.Soundness
a)By Le Chateliers apparatus 1.00 mm 10 mm
3.Setting time (minutes)
a) Initial set 195 minutes 30 minutes
b) Final set 255 minutes 600 minutes
4.Comp strength (M Pa)
a) 3 days 32 23 MPa
b) 7 days 41 33 MPa
c) 28 days 52 43 MPa
Temperature during testing 27.810 C 27° C 2%
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3.1.2 COMPOSITION OF ORDINARY PORTLAND CEMENT
Table 3.2 Composition of Ordinary Portland cement
INGRADIENTS COMPOSITION PERCENTAGE
Lime CaO 62
Silica SiO2 22
Alumina Al2 O3 05
Calcium Sulphate CaSO4 04
Iron Oxide Fe2O3 03
Magnesia MgO 02
Sulphur S 01
Alkalies --- 01
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3.1.3 FINE AGGREGATE
The sand used for the experimental program was locally procured and was
conforming to zone-II according to code IS 383:1970. The specific gravity of fine aggregate
was found to be 2.89.
Table 3.3 Sieve Analysis of Fine Aggregate
3.1.4 COARSE AGGREGATE
Locally available coarse aggregate having the maximum size of 20 mm were used in
the present work. The specific gravity of coarse aggregate was found to be 2.82.
3.1.5 RICE HUSK ASH
Rice husk ash is obtained from the local rice mill in Davanagere. Which is burnt in
furnace and the process of burning is uncontrolled.The specific gravity of rice husk ash was
found to be 2.3.
3.1.6 WATER
Portable tap water was used for the preparation of specimens and for the curing of
specimens. Portable water as available in GMIT campus was used for the preparation of
mortar mix. The PH value of water is 6.8.
SL
NO
IS SIEVE
SIZE
Weight
Retained
(Kg)
Cumulative
Weight
Retained
(Kg)
Cumulative
Percentage
Retained
Cumulative
Percentage
Passing
1 4.75 6 6 0.6 99.4
2 2.36 42 48 4.8 95.2
3 1.18 229 277 27.7 72.3
4 600 µ 348 625 62.5 34.5
5 300 µ 225 880 88 12.0
6 150 µ 115 995 99.5 0.5
7 Pan 5 1000 100 0
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3.2 METHODOLOGY
The main objective of this work is to study the suitability of the rice husk ash as a
pozzolanic material for cement replacement in concrete. However it is expected that the use
of rice husk ash in concrete improve the strength properties of concrete. Also it is an attempt
made to develop the concrete using rice husk ash as a source material for partial replacement
of cement, which satisfies the various structural properties of concrete like compressive
strength and split tensile strength.
It is also expected that the final outcome of the project will have an overall beneficial
effect on the utility of rice husk ash concrete in the field of civil engineering construction
work.
Following parameters influences behavior of the rice husk ash concrete, so these
parameters are kept constant for the experimental work.
Percentage replacement of cement by rice husk ash
Fineness of rice husk ash
Chemical composition of rice husk ash
Water to cementitious material ratio (w/c ratio)
Type of Curing
Also from the literature survey, it is observed that the parameters suggested by
different researchers and their results are not matching with each other. It was due to
variation in properties of different materials considered in the work. Therefore the percentage
replacement of cement by rice husk ash and method of mix design is fixed after preliminary
investigation.
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3.3 CONCRETE MIX DESIGN
We have designed the mix as per the mix design in accordance with the Indian
standard recommended guide lines for concrete mix design.
The mix design procedure adopted to obtain a M20 grade concrete is in accordance
with IS 10262- 2009.The specific gravities of the materials used are as tabulated in the table
a) Design Stipulations:
i. Characteristic Compressive Strength of cement:43N/mm2
ii. Maximum size of the aggregates: 20 mm
b) Test data for Materials:
i. Specific Gravity of Cement: 3.15
ii. Specific Gravity of Coarse Aggregate: 2.82
iii. Specific Gravity of Fine Aggregate:2.89
iv. Concrete Designation: M20
v. Characteristic Compressive Strength (fck):20 N/mm2
vi. Water Absorption:
a. Coarse Aggregates:0.5%
b. Fine Aggregate:1.04%
vii. Free (Surface) Moisture
a. Coarse Aggregate:0.5%
b. FineAggregate: 2.0%
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The design steps are as follows
Step 1: Determination of the target strength for mix proportioning
fck = fck+ 1.65s
Where, fck = target mean compressive strength at 28 days
fck = characteristics compressive strength at 28 days
s = standard deviation.
From IS 456-2000, Table 8, s = 4MPa
Therefore target strength = 20 + (1.65 4) = 26.6 MPa.
Step 2: Selection of water /cement ratio
Referring IS 456-2000, Table 5, W/C ratio = 0.55
Step 3: Selection of water content
From Table 2 IS 10262-2009, maximum water content = 186 liter (for 25to 50 mm slump
range) for 20 mm aggregate. Estimated water content for 100 mm slump
=186+6/100*186=197 liter.
Step 4: Calculation of cement content
W/C ratio = 0.55
Therefore, cement content = 197 / 0.55
= 358.18 Kg/m3.
Referring to IS 456- 2000, Table 5, Minimum cement required = 320 Kg/m3< 358.18 Kg/m
3
Hence the cement content is adequate.
Step 5: Determination of the volume of coarse aggregates
Referring IS 10262- 2009, Table 3, volume of coarse aggregate per unit volume of concrete
corresponding to a maximum size of coarse of 20mm and fine aggregate corresponding to
grading zone II,
Volume of coarse aggregate= 0.62-0.01= 0.61
Volume of fine aggregate content=1-0.61= 0.39
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Step 6:Mix Calculations
Volume of concrete = 1 m3
Volume of cement = Weight / Specific gravity
= (325 / 3.15) (1 / 103)
= 0.116 m3
Volume of Water = Weight / Specific gravity
= 197 / 1000
= 0.197 m3
Volume of Coarse aggregate = 0.61 m3
Volume of Fine Aggregate = 1 – 0.116 – 0.197 – 0.62
= 0.067 m3
Total quantity of aggregates = 1 – 0.116 – 0.197
= 0.687 m3
Mass of coarse aggregate = 0.687 0.61 2.82 103
= 1186.9 Kg/m3
Mass of fine aggregate = 0.687 0.39 2.82 x 103
= 777.69 Kg/m
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Step 7: The mix proportion obtained are as shown in the table 3.3.
Table 3.4 Mix Proportion
W/C Ratio Cement Fine Aggregate Coarse Aggregate
0.55 358.18 kg/m3 777.69 kg/m
3 1186.9 kg/m
3
0.55 1 2.17 3.31
Table 3.5 Mix Proportion for Different % of RHA
Mix
Designation
Rice husk
ash
Cement
Kg/m3
Coarse
Aggregate
Kg/m3
Fine
Aggregate
Kg/m3
Water
Liters/m3
M0 0% 358.18 1186.90 777.69
197
M1 5% 340.28 1183.20 775.3
197
M2 10% 322.37 1181.77 774.31
197
M3 15% 304.45 1178.83 772.06
197
M4 20% 286.55 1174.89 769.8
197
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3.4 CONCRETE MIX DESIGNATION
Table 3.6 Concrete Mix Designation
Mix Designation
Description
M0 control concrete of grade M20
M1 5% RHA + 95% Cement
M2 10% RHA +90% Cement
M3 15% RHA +85% Cement
M4 20% RHA +80% Cement
3.5 CASTING OF SPECIMENS AND TESTING PROCEDURE
Cement, sand and aggregate were taken in mix proportion 1:2.17:3.31 which
correspond to M20 grade of concrete. 0%, 5%, 10%, 15%, & 20% of cement was replaced by
RHA and concrete was produced by dry mixing all the ingredients homogeneously. To this
dry mix, required quantity of water was added (W/C= 0.55) and the entire mix was again
homogeneously mixed. This wet concrete was poured into the moulds which was compacted
both through hand compaction in three layers as well as through vibrator. The specimens
were given smooth finish and taken out of the table vibrator. After the compaction, the
specimens were given smooth finishes and were covered with gunny bags. After 24 hours,
the specimens were demoulded and transferred to curing tanks where in they were allowed to
cure for 28 days.
For evaluating the compressive strength, specimens of dimensions 150x150x150mm
were prepared. They were tested on compression testing machine as per IS 516-1959. The
compressive strength is calculated by using the equation,
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F=P/A ………..8
Where, F= Compressive strength of the specimen (in MPa).
P= Maximum load applied to the specimen (in N).
A= Cross sectional area of the specimen (in mm2).
For the evaluating the tensile strength, cylindrical specimens of diameter 150mm and length
300mm were prepared. Split tension test was carried out on 2000 kN capacity compression
testing machine as per IS 5816-1999. The tensile strength is calculated using the equation,
F= 2P/ (πDL) ……….9
Where, F = Tensile strength of concrete (in MPa).
P = Load at failure (in N).
L = Length of the cylindrical specimen (in mm).
D = Diameter of the cylindrical specimen (in mm).
Three concrete cubes and two cylinders are cast for compression test at 7,14 and 28 days .Fig
3.1 shows the test specimens
Fig 3.1 Casting of Cubes and cylinders
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Fig 3.2 Testing of Cubes and cylinders
3.6 SLUMP VALUES:
Table 3.7 Slump Values
SL NO MIX DESIGNATION SLUMP VALUES(MM)
1 M0 95
2 M1 85
3 M2 70
4 M3 55
5 M4 40
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Fig 3.3 Slump Variation
The slump values decreased upon the inclusion of RHA as partial replacement of
OPC.Thus, it can be inferred that to attain the required workability, mixes containing RHA
will required higher water content than the corresponding conventional mixes.
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20
Slu
mp
va
lue
in m
m
RHA in percentage
Slump Values
slump value
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CHAPTER 4
EXPERIMENTAL RESULT
4.1 COMPRESSIVE STRENGTH TEST RESULTS
For each concrete mix, the compressive strength is determined on three 150×150×150
mm cubes at 7, 14 and 28 days of curing.
Following tables 4.1,4.2 & 4.3give the compressive strength test results of control
concrete and RHA concrete produced with 5, 10, 15, & 20 percentages of RHA.
Table 4.1 Compressive strength of RHA concrete for 7 days
Mix
Designation
Curing
period
Failure load
(KN)
Compressive
strength (N/mm2)
Avg
Compressive
strength
(N/mm2)
M0
7 days
640 28.44
29.03 680 30.22
640 28.44
M1 7 days
510 22.66
21.7 475 21.11
480 21.33
M2 7 days
260 11.55
13.55 385 17.11
270 12
M3
7 days
320 14.22
11.77 260 11.55
215 9.55
M4 7 days
280 12.44
10.81 240 10.66
210 9.33
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Table 4.2 Compressive Strength of RHA Concrete For 14days
Mix
Designation Curing period
Failure load
(kN)
Compressive
strength
(N/mm2)
Avg
Compressive
strength
(N/mm2)
M0
14 days
790 35.11
35.03 795 35.33
780 34.66
M1 14 days
580 25.77
24.95 575 25.55
530 23.55
M2 14 days
330 14.66
19.44 480 21.33
500 22.33
M3
14 days
390 17.33
18.07 420 18.66
410 18.22
M4 14 days
300 13.33
14.66 365 16.22
325 14.44
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Table 4.3 Compressive Strength Of RHA Concrete For 28days
Mix
Designation
Curing
period
Failure load
(KN)
Compressive
strength
(N/mm2)
Avg
Compressive
strength
(N/mm2)
M0
28 days
980 43.55
44.58 1020 45.33
1010 44.88
M1 28 days
770 34.22
36.88 900 40.00
820 36.44
M2 28 days
690 30.66
29.18 620 27.55
660 29.33
M3
28 days
470 20.88
20.07 455 20.22
430 19.11
M4 28 days
320 14.22
14.59 340 15.11
325 14.44
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4.1.1 OVERALL RESULTS OF COMPRESSIVE STRENGTH
Following table gives the overall results of compressive strength of RHA concrete
produced with different percentages of RHA. The variation of compressive strength is
depicted in the form of graph as shown in figure 4.4
Table 4.4 Overall Results of Compressive Strength
Mix designation
Compressive strength (N/mm2)
7 days curing
14 days curing 28 days curing
M0 29.03 35.03 44.58
M1 21.70 24.95 36.88
M2 13.55 19.44 29.18
M3 11.77 18.07 20.07
M4 10.81 14.66 14.59
Fig 4.1 Compressive Strength of RHA Concrete For 7 Days
0
5
10
15
20
25
30
35
0 5 10 15 20
com
pre
ssiv
e st
ren
gth
in
N/m
m2
RHA in percentage
Compressive Strength For 7 Days
7 days
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Fig 4.2 Compressive Strength of RHA Concrete for 14 Days
Fig 4.3 Compressive Strength of RHA Concrete For 28 Days
Fig 4.3 Compressive Strength of RHA Concrete for 28 Days
0
5
10
15
20
25
30
35
40
0 5 10 15 20
com
pre
ssiv
e st
ren
gth
in
N\m
m2
RHA in percentage
Compressive Strength For 14 days
14 days
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20com
pre
ssiv
e st
ren
gth
in
N/m
m2
RHA in percentage
Compressive Strength of RHA For 28 days
28 days
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Fig 4.4 Overall Results of Compressive Strength
Fig 4.5 Overall Results of Compressive StrengthVGV
Fig 4.5 Overall Results of Compressive Strength
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20
7 days
14 days
28 days
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20
com
pre
ssiv
e st
ren
gth
in
N/m
m2
RHA in percentage
7 days
14 days
28 days
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4.2 SPILT TENSILE STRENGTH TEST RESULTS
Test has been conducted after 7, 14 and 28 days of curing. Split tensile is conducted on
150 mm diameter and 300 mm length cylinders as per IS 5816-1999.
Following tables 4.5, 4.6 & 4.7 gives the split tensile strength test results of control concrete
and RHA concrete produced with 0,5,10, 15, & 20 percentages of RHA.
Table 4.5 Split Tensile Strength of RHA Concrete for 7 Days
Mix Designation Curing
period
Failure load
(kN)
Tensile
strength
(N/mm2)
Avg Tensile
strength (N/mm2)
M0 7 days 130 1.89 1.93
140 1.98
M1 7 days 175 2.47 2.01
110 1.55
M2 7 days 110 1.55 1.51
105 1.48
M3
7 days 100 1.41 1.30
85 1.20
M4 7 days 70 0.99 0.91
60 0.84
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Table 4.6 Split Tensile strength of RHA concrete for 14 days
Mix Designation Curing
period
Failure load
(kN)
Tensile
strength
(N/mm2)
Avg Tensile
strength
(N/mm2)
M0
14 days 155 2.19
2.29
170 2.40
M1 14 days 180 2.54
2.21
130 1.89
M2 14 days 130 1.83
1.79
125 1.76
M3
14 days 85 1.20
1.13
75 1.06
M4 14 days 135 1.90
1.79
120 1.69
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Table 4.7 Split Tensile strength of RHA concrete for 28 days
Mix Designation Curing period Failure load
(KN)
Tensile
strength
(N/mm2)
Avg
Tensile
strength
(N/mm2)
M0
M0
28 days 210 2.97
3.11
230 3.25
M1
28 days 175 2.47
2.43
170 2.40
M2 28 days 170 2.47
2.64
200 2.82
M3
28 days 120 1.69
1.83
140 1.98
M4 28 days 100 1.41
1.58
125 1.76
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4.2.1 OVERALL RESULTS OF SPLIT TENSILE STRENGTH
Following table gives the overall results of split tensile strength of RHA concrete
produced with different percentages of RHA. The variation of tensile strength is depicted in
the formof graph as shown in figure.
Table 4.8 Overall results of split tensile strength
Mix Designation
SplitTensile strength (N/mm2)
7 Days Curing 14 Days Curing 28 DaysCuring
M0 1.93 2.29 3.11
M1 2.01 2.21 2.43
M2 1.51 1.79 2.64
M3 1.30 1.13 1.83
M4 0.91 1.79 1.58
Fig 4.6 Split Tensile Strength of RHA Concrete for 7 Days
0
0.5
1
1.5
2
2.5
0 5 10 15 20
spli
t te
nsi
le
stre
ng
th i
n N
/mm
2
RHA in percentage
Split Tensile Strength For 7 Days
7 days
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Fig 4.7 Split Tensile Strength of RHA Concrete For 14 Days
Fig 4.8 Split Tensile Strength of RHA Concrete for 28 Day
0
0.5
1
1.5
2
2.5
0 5 10 15 20
spli
t te
nsi
le s
tren
tgh
in
N/m
m2
RHA in percentage
Split Tensile Strength For 14 days
14 days
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Sp
lit
ten
sile
str
en
gth
in
N/m
m2
RHA in percentage
Split Tensile Strength For 28 Days
28 days
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Fig 4.9 Overall Split Tensile Strength
Fig 4.10 Overall Split Tensile Strength
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Sp
lit
ten
sile
str
en
gth
in
N/m
m2
RHA in percentage
7 days
14 days
28 days
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
7 days
14 days
28 days
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CHAPTER- 5
OBSERVATION AND DISCUSSIONS
The results of compressive strength of concrete cubes show that the compressive
strength reduced as the percentage of RHA increased. However the compressive strength
increased as the number of days of curing increased for each percentage RHA replacement. It
is seen from table 4.1&4.3 that for control cube the compressive strength increased from
29.03 N/mm2 at 7 days to 44.58 N/mm
2 at 28 days. The 28days strength was above the
specified value of 20N/mm2
for grade M20 concrete. The strength of 5% replacement by
RHA showed increase in compressive strength from 21.7 N/mm2 at 7 days to 36.88 N/mm
2 at
28 day, the 28 days strength was above the specified value of 20 N/mm2 for grade M20
concrete. The strength of 10% replacement by RHA showed increased in compressive
strength from 13.55N/mm2 at 7 days to 29.18N/mm
2 at 28days. The 28days strength was
above the specified value of 20N/mm2 for grade M20 concrete as shown in table 5.1. The
strength of 15% replacement by RHA should increases in compressive strength from
11.77N/mm2 at 7days to 20.07N/mm
2 at 28 days. The 28days strength was above the
specified value of 20N/mm2 for precast products as shown in table. The strength of the 20%
replacement by RHA showed increase in compressive strength 10.81N/mm2 at 7days to
14.59N/mm2 at 28days. The 28 days strength was above the specified value of 10 N/mm
2 for
huge concrete works for foundations, culverts and retaining walls as shown in table 5.1.
Table 5.1 Uses of different grades of concrete
SL No Grade Concrete Mix Uses
1 M10 1:3:6 Mass concrete in piers, abutments,
2 M15 1:2:4 Normal RCC works i.e., slabs, columns, walls.
3 M20 1:1.5:3 Water retaining structures, reservoirs.
4 M25 1:1:2 Long span arches and highly loaded columns
5 M30 - Mass concrete foundations
6 M35 - Post tensioned prestressed concrete
7 M40 - pre tensioned prestressed concrete
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CHAPTER -6
CONCLUSION
Based on the limited experimental investigation concering Compressive and split
tensile strength of concrete with rice husk ash as a partial replacement of cement, the
following conclusion can be drawn.
1. As the rice husk ash is a waste material, it reduces the cost of construction.
2. The optimum replacement level of RHA is found to be 0-15% for M20 grade of
concrete.
3. The replacement of cement with RHA results in reduction of density of concrete. This is
due to the fact that the specific density of the RHA is much lower than that of cement.
4. The slump values of the concrete reduced as the percentage of RHA increased.
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CHAPTER -7
REFERENCES
1 A.M.Naville and J.J.Brooks, (1999) Concrete Technology, Addison- Wesley, First
Reprint 1999.
2 Dao van dong, Pham duy and Nguyen ngoclan . (2008), “Effect of Rice Husk Ash on
Properties of High Strength Concrete”.
3 Ghassan Abood Habeeb, Hilmi Bin Mahmud., (2009), “Study on Properties of Rice
Husk Ash and Its Use as Cement Replacement Material”, vol.13, pp.2.
4 Monikachanu N ,Dr.Th.Kiranbala Devi(2011)”Contribution of RHA to the properties of
cement mortar and concrete” IJER,volume-2,ISSN:2278-018,pages 3-7.
5 Deepa G Nair ,K..Sivaraman and Job Thomas(2013) “Mechanical properties of RHA –
High strength concrete “,AJER,volume-3,ISSN:2320-0847,pages 14-18.
6 Anil kumarsuman, Anil kumarsaxena, T.R.Arora(2015) “Assessment of concrete
strength using partial replacement of cement for RHA”, international journal,vol-4,ISSN :
2231-2307, pages 131-133.
7 IS:10262-2009 “specification for concrete mix proportioning”, BIS 2009
8 IS:456-2000 “Plain and reinforced concrete - code of practice” BIS 2000
9 IS:9103-1999 “Specification for Concrete admixture” BIS 1999
10 IS:383-1970 “Specification for coarse and fine aggregate” BIS 1970
11 IS 5816-1999 “Specification for splitting tensile strength” BIS 1999
12 IS:8112-1989 “specification for 43 grade ordinary Portland cement” BIS 1989
13 M.S.Shetty “Concrete Technology”, S.Chand and Company Ltd, 2008.