CHAPTER-4 MATERIALS AND EXPERIMENTATION …shodhganga.inflibnet.ac.in/bitstream/10603/10020/11/10...d) Fineness Modulus of Fine Aggregate The coarse aggregate of sizes 20mm and 12.5mm

54

CHAPTER-4

MATERIALS AND EXPERIMENTATION

4.1 GENERAL

The present chapter deals with the properties of materials used in this

investigation. The various materials used in this investigation are cement, fine

aggregate, metakaolin, phosphogypsum, superplasticizer, various chemicals and

water. This chapter also highlights the testing of materials used in this investigation.

4.2 MATERIALS

The materials used in this experimental investigation include

1. Cement

2. Coarse aggregate

3. Fine aggregate

4. Metakaolin

5. Phosphogypsum

6. Water

7. Super-plasticizer Glenium B-233

8. NaCl, KCl, Na2SO4, CaCO3, Na2CO3, NaHCO3, CaCl2, MgSO4, HCl and

H2SO4 with different concentrations in mixing water.

4.2.1 Cement

Ordinary Portland cement of 53 grade conforming to ISI standards has been

procured. Following tests have been carried out according to IS: 8112 – 1989 on the

cement samples.

a) Specific gravity of Cement

b) Normal Consistency of Cement

c) Initial and Final setting time of Cement

55

d) Compressive Strength of Cement

e) Chemical compositions

The results of above tests are presented in Tables 4.1 and 4.2

Table 4.1: Physical properties of Cement

S.No Property Values

1 Fineness of Cement 225 m2/kg

2 Specific Gravity 3.1

3 Normal Consistency 29 %

4

Setting Time

i) Initial Setting time

ii) Final setting time

105 mins

350 mins

5

Compressive Strength

i) 3 days

ii) 7 days

iii) 28 days

32 N/mm2

46 N/mm2

58 N/mm2

Table 4.2: Chemical composition of cement

Lime (CaO) 63.70 %

Silica (SiO2) 22.00 %

Alumina (Al2O3) 4.25 %

Iron Oxide (Fe2O3) 3.40 %

Magnesia (MgO) 1.50 %

Sulphur trioxide 1.95 %

56

4.2.2 Fine aggregate and Coarse aggregate

The locally available river sand conforming to grading zone-II of Table 4 of IS

383-1970 has been used as Fine Aggregate. Following tests have been carried out as

per the procedure given in IS 383-1970 and the results are presented in Tables 4.3 &

4.4.

a) Specific Gravity

b) Bulk Density

c) Grading

d) Fineness Modulus of Fine Aggregate

The coarse aggregate of sizes 20mm and 12.5mm have been used. The

properties of these are presented in tables 4.5, 4.6 and 4.7.

Table.4.3: Sieve Analysis of Fine aggregate

S.

No.

I.S Sieve

Designation

Weight

retained

gm

Cumulative

weight

retained

Cumulative

percentage

retained

Cumulative

percentage

Passing

1 10mm 0 0 0 100

1 4.75mm 0.021 0.021 2.10 97.9

2 2.36mm 0.039 0.060 6.00 94

3 1.18mm 0.180 0.240 24.00 76

4 600 0.316 0.556 55.60 44.4

5 300 0.355 0.911 91.10 8.9

6 150 0.075 0.986 98.60 1.4

7 Pan 0.014 1 -------- -----------

Total = 277.4

Fineness Modulus = 2.77

57

Table4.4: Physical Properties of Fine aggregate

S. No. Property Value

1 Specific Gravity 2.69

2 Fineness Modulus 2.77

3 Bulk Density

i) Loose

ii) Compacted

14.57 kN/m3

16.25 kN/m3

4 Grading Zone - II

Table 4.5: Physical properties of Coarse aggregate

S.No Property Values

20mm 12.5mm

1 Specific Gravity 2.70 2.70

2

Bulk Density

i) Loose State

ii) Compacted

State

15.36 KN/m3

17.26 KN/m3

14.13 KN/m3

16.88 KN/m3

3 Water Absorption 0.2% 0.3%

4 Flakiness Index 9% 14.22%

5 Elongation Index 12% 21.33%

6 Crushing Value 13.45% 21.43%

7 Impact Value 11.26% 15.5%

8 Fineness Modulus 5.411 4.352

58

Table 4.6 Sieve Analysis of Coarse aggregate (20 mm)

S. No

IS Sieve

Weight

retained

(kg)

Cumulative

Weight

retained

(kg)

Cumulative

% weight

retained

Cumulative

% Passing

1 40 mm 0 0 0 100

2 20 mm o.305 0.305 6.1 93.9

3 16 mm 2.560 2.865 57.3 42.7

4 12.5mm 1.320 4.185 83.7 16.3

5 10mm 0.570 4.755 95.1 4.9

6 4.75 mm 0.200 4.955 99.1 0.9

7 2.36 mm 0.035 4.99 99.8 0.2

8 1.18mm 0.010 5 100 0

Fineness modulous=5.411

Table 4.7 Sieve Analysis of Coarse aggregate (12.5 mm)

S. No

IS Sieve

Weight

retained

(kg)

Cumulative

Weight

retained (kg)

Cumulative

% weight

retained

Cumulative

% Passing

1 20 mm 0 0 0 100

2 16 mm 0.445 0.445 8.9 91.1

3 12.5 mm 1.260 1.705 34.1 65.9

4 10 mm 2.970 4.675 93.5 6.5

5 4.75 mm 0.280 4.955 99.1 0.9

6 2.36mm 0.025 4.980 99.6 0.4

7 1.18mm 0.020 5 100 0

Fineness Modulus = 4.352

59

Fig: 4.1 View of cement, fine aggregate and coarse aggregate

4.2.3 Properties of Metakaolin

Metakaolin obtained from KOAT manufacturing company, Vadodara, Gujarat

has been used. Metakaolin is a dehydroxylated form of the clay mineral

kaolinite.Rocks that are rich in kaolinite are known as china clay or kaolin,

traditionally used in the manufacture of porcelain. The particle size of metakaolin is

smaller than cement particles, but not as fine as silica fume. Metakaolin is

a pozzolanic additive product which can provide many specific features. It is available in

many different varieties and qualities. The purity will define the binding capacity for free

lime. Some of them also provide special reactivity.

Metakaolin is a valuable admixture for concrete applications. Usually 8% - 20%

(by weight) of Portland cement is replaced by metakaolin. Such a concrete exhibits

favorable engineering properties. The pozzolanic reaction starts soon and continues

between 7 to 28 days.

60

Fig. 4.2 View of the metakaolin

Table 4.8: Physical properties of metakaolin (KOAT manufacturing company,

Vadodara, Gujarat)

S.No Property Value

1 Brightness(ISO) 82±2

2 Yellow index 2.2 to 2.5

3 Bulkdensity(gm/L) 300 to 340

4 Average particle size 1.5 to 2.5 micron

5 Residue (>45 micron) (max%) 0.5 to 2 %

6 Moisture content ≤1%

7 Specific surface area BET (m2

/gm) 12-18

Table 4.9: Chemical properties of metakaolin

(KOAT manufacturing company, Vadodara, Gujarat)

S.No Chemical analysis Percentage

1 SiO2 51-54%

2 Al2O

3 41-44%

3 Fe2O

3 0.35%

4 TiO2 0%

5 CaO 0.02%

6 MgO 0.07%

7 K2O 1-2%

8 Na2O 0.13%

61

4.2.4 Properties of Phosphogypsum

The Phosphogypsum used in the investigation was obtained from Coromandel

international Ltd, Ennore, Chennai. The Phosphogypsum passing through 90 sieve

was used throughout the experiment. The specific gravity of Phosphogypsum was

found to be 2.34. The properties of PG used in this study are presented in Table 4.10.

Table 4.10: Chemical composition of phosphogypsum (Coromandel international

Ltd, Ennore, Chennai)

S.No Chemical Percentage

1 CaSO42H2O 92.0-94.0

2 SiO2+insolubles 4.0 max

3 Fe2O3+Al2O3 0.3 max

4 CaO 30.0-31.0

5 MgO 0.1 max

6 Na2O+K2O 0.3-0.4 (0.5 max)

7 Total P2O5 0.6-1.0

8 Total SO3 42.8-44.0

9 Fluorides as F 0.4-0.5(0.7 max)

10 Chlorides as C 0.3-0.5(0.6 max)

11 pH of 10% solution 5.0-6.0(4 min)

62

Fig.4.3: View of phosphogypsum

4.2.5 Properties of Water

Deionised water has been used for mixing as well as curing of concrete in the

present investigation. The characteristics of deionised water, to which various

chemical substances were spiked to obtain neutral salt, strong alkaline, slightly acidic

and acidic water, are presented in the table

Table 4.11: Characteristics of Deionised Water

SI. No. Parameter Amount

1 pH 9.7

2 TDS(mg/L) 6.5

3 Alkalinity(mg/L) 9

4 Acidity(mg/L) 2

5 Hardness(mg/L) 1

6 Sulphates(mg/L) 0.3

7 Chlorides(mg/L) 9

63

The control sample which is prepared with deionised water as mixing water

and did not contain any chemical additives was used as the basis of comparison for

examining the effects of the chemicals on the properties of HPC.

4.2.6 Properties of Superplasticizer

GLENIUM B233 is an admixture of a new generation based on modified

polycarboxylic ether. The product has been primarily developed for applications in

high performance concrete where the highest durability and performance is required.

GLENIUM B233 is free of chloride & low alkali. It is compatible with all types of

cements.

Uses

Production of Rheodynamic concrete

High Performance Concrete for Durability

High early and Ultimate Strength Concrete

High Workability without segregation or bleeding

Precast or Pre-stressed concrete

Concrete containing pozzolans such as microsilica , GGBFS ,PFA including

high volume fly ash concrete

Advantages

Elimination of vibration and reduced labour cost in placing

Marked increase in early & Ultimate Strengths

Higher E modulus

Improved adhesion to reinforcing and stressing steel

64

Better resistance to Carbonate and other aggressive atmospheric conditions

Lower permeability – increased durability

Reduced shrinkage and creep

Dosage

Optimum dosage of GLENIUM B233 was found out by Marsh cone test. A

graph was plotted connecting marsh cone time in seconds and dosage of

superplasticizer. The dose at which the Marsh cone time is lowest is called the

saturation point. That dose is taken as the optimum dosage. In the present

investigation 1% by weight of cement is the optimum dosage.

Typical properties as supplied by the manufacturer:

Aspect: Light brown liquid

Relative Density: 1.08 ± 0.01 at 25°C

pH: >6

Chloride ion content: < 0.2%

Effects of over dosage:

Extension of initial and final set

Bleed/Segregation of mix , quick loss of workability

Increased plastic shrinkage

65

Fig4.4: Chemical admixture GLENIUM B233

4.2.7. Chemical substances

From the past literature various researchers have collected water samples from

different water bodies and also from various industrial chemical effluents were

collected and analysed for chemical and biological components. Among these

components, the most commonly found components were identified along with their

concentrations in treated effluents. Based on this information various chemical

components were selected for the experimental work. The chemical substances were

further categorized in to four major divisions viz., i) Neutral salts ii) Strong Alkaline

substances iii) Slightly Acidic substances and iv) Strong Acids.

Table 4.12 below gives the list of chemical substances along with the range of

concentrations and pH values in effluents.

66

Table 4.12: Classification and details of chemical substances

4.3. EXPERIMENTATION

4.3.1. Test Programme

The details of the specimens used in the experimental work are presented in

Table 4.13. A total of 288 samples of standard moulds used in Vicat’s apparatus were

cast and tested for initial and final setting time experiments. A total of 432 samples of

concrete were used in compaction factor test and 432 samples of concrete were used

in vee-bee time test. A total of 1296 concrete cubes of (15x15x15 cm) 225 cm2 cross-

S. No. Name & symbol Range of

concentration

Range of

pH

1

Neutral salts

a) NaCl

b) KCl

c) Na2SO4

d) CaCO3

0 – 30 g/L

0 – 5 g/L

0 – 20 g/L

0 – 0.3 g/L

7.0-7.01

7.0-7.05

7.0-7.04

6.9-7.1

2

Strong Alkaline

substances

a) Na2CO3

b) NaHCO3

0 – 20 g/L

0 – 20 g/L

8.3-11.20

7.6-9.7

3

Slightly Acidic

substances

a) CaCl2

b) MgSO4

0-2 g/L

0-1.5 g/L

7.2-6.2

7.10-6.13

4

Strong Acids

a)HCl

b)H2SO4

0-800 mg/L

0-800 mg/L

4.3-6.03

4.3-6.03

67

sectional area were tested at 7 days, 28 days and 90 days for compressive strength.

The same number of cylindrical samples of 15x15x30 cm3 were tested for split tensile

strength at 7 days, 28 days, and 90 days.

Table: 4.13: Details of test Programme

SNo.

Chemical Concent

ration

No. Of

Specimens

for

Setting

time test

No. Of

Specimens

for

compaction

factor test

No. Of

Specimens

for vee-

bee time

test

No. Of

Specimens

for

Compression

test

No. Of

Specimen

s

for Split

tensile

test To

tal

1 Deionised water

(control) -

3x2

3x3

3x3

3X 9

3X 9

78

2

NaCl (g/L)

0.5

2.0

4.0

10.0

20.0

30.0

3x2

3x2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

78

78

3

KCl (g/L)

0.5

1.0

2.0

3.0

5.0

3x2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

78

4

Na2SO4 (g/L)

0.5

2

4

6

10

20

3x2

3x2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

78

78

68

5

CaCO3 (g/L)

0.01

0.1

0.2

0.3

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

6

Na2CO3(g/L)

0.5

2

4

10

20

3x2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

78

7

NaHCO3(g/L)

0.5

2

4

10

20

3x2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

78

8

CaCl2(g/L)

0.2

0.5

1

2

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

9

MgSO4(g/L)

0.2

0.5

1

1.5

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

10

HCl(mg/L)

50

100

400

800

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

11

H2SO4(mg/L)

50

100

400

800

3x2

3x2

3x2

3x2

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3x3

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

3X 9

78

78

78

78

Total 288 432 432 1296 1296 3744

69

4.3.2 Experimental Procedure

Normal consistency, initial and final setting times are determined by the

Vicat’s apparatus, which measures the resistance of cement paste of standard

consistency of the penetration of a needle under a total load of 300gm. The initial set

is an arbitrary time in the setting process, which is reached when the needle is no

longer able to pierce 40mm deep pat of the cement paste within about 5 to 7 mm from

the bottom. The final set is reached, when the needle makes an impression on the

surface of the paste but does not penetrate.Vicat’s apparatus confirming to IS 5513-

1976 consists of a frame to which a movable rod having an indicator is attached

which gives the penetration. The rod weighs 300 gm and has diameter and length of

10 mm and 50 mm respectively. Vicat’s apparatus includes three attachments –

plunger for determining normal consistency, square needle for initial setting time, and

needle with annular collar for final setting time. Detailed experimental procedures

adopted in the investigation are given in the following sections.

Fig.4.5: Vicat’s apparatus

70

4.3.2.1. Consistency

About 300gm of cement was initially mixed with 27 percent mixing water.

The paste was filled in the mould of Vicat’s apparatus and care was taken such that

the cement paste was not pressed forcibly in the mould and the surface of the filled

paste was not pressed forcibly in the mould and surface of the filled paste was

smoothened and leveled. A square needle of size 1 mm x 1mm x 1mm attached to the

plunger is then lowered gently on to the surface of the cement paste and is released

quickly. The plunger pierces the cement paste and the reading on the attached scale

was recorded. The experiment was performed carefully, away from vibrations and

other disturbances. The test procedure was repeated by increasing the percentage of

mixing water at 0.5% increment until the reading was 5 to 7 mm from the bottom of

the mould. When this condition is fulfilled, the amount of water added was taken as

the correct percentage of water for normal consistency. The entire test was completed

within 3 to 5 minutes. Fresh sample was taken for each repetition of the experiment.

The plunger was cleaned each time the experiment is done.

4.3.2.2 Initial setting time

Lower the needle gently and bring it in contact with the surface of the test

block and quickly release. Allow it to penetrate in to the test block .In the beginning

the needle will completely pierce through the test block. But after some time when the

paste starts losing its plasticity the needy may penetrate only to a depth of 33 – 35mm

from the top .The period elapsing between the time when water is added to the cement

and the time at which the needle penetrates the test block to a depth equal to 33-35mm

from the top is taken as initial setting time.

71

4.3.2.3. Final setting time

The cement shall be considered as finally set when , upon , lowering the

attachment gently cover the surface of the test block ,the center needle makes an

impression , while the circular cutting edge of the attachment fails to do so. In other

words the paste has attained such hardness that the centre needle does not pierce

through the paste more than 0.5mm.

4.3.2.4. Workability

All the mixes were evaluated for workability in terms of compaction factor

and vee-bee time.

4.3.2.4.1. Compaction factor test

The apparatus for conducting compaction factor test is depicted in Fig: 4.6.

The compaction factor test apparatus consists of two hoppers, each in the shape of

frustum of a cone and one cylinder. The upper hopper is filled with concrete this

being placed gently so that no work is done on the concrete at this stage to produce

compaction. The second hopper is smaller than the upper one and is therefore filled to

overflowing. The concrete is allowed to fall in to the lower hopper by opening the trap

door and then into the cylindrical mould placed at the bottom. Excess concrete across

the top of the cylindrical mould is cut and the net weight of the concrete in cylinder is

determined. This gives the weight of partially compacted concrete. Then the

cylindrical mould is filled with concrete in layers of 5cm depth by compacting each

layer fully. The fully compacted weight is then determined and compaction factor

(C.F) is calculated as below.

Weight of partially compacted concrete

C.F. = -----------------------------------------------

Weight of fully compacted concrete

72

Fig. 4.6: View of the test setup for Compaction Factor

4.3.2.4.2 Vee-bee time test

The Vee-Bee consistometer test is suitable for mixes with low workability

whose slump cannot be measured with slump test. Since low water-binder ratios are

adopted in the production of HPC, this V-B test is quite suitable to find out the

workability. The apparatus for conducting Vee-Bee test is depicted in Fig. 4.7.

Placing the slump cone inside the metal cylindrical pot of consistometer the slump

test is performed. The glass disc attached to the swivel arm is turned and placed on

the top of the concrete in the pot. The electrical vibrator is then switched on and

simultaneously a stopwatch is started. The vibration is continued till such a time as

the conical shape of concrete disappears and the concrete attains a cylindrical shape.

This can be judged by observing the glass disc from the top for disappearance of

73

transparency. Immediately when the concrete fully attains a cylindrical shape, the

stopwatch is switched off. The time required for the concrete to change from slump

cone to cylindrical shape in seconds is known as Vee-Bee degree.

Fig.4.7: View of the test setup for Vee-Bee Time

4.3.2.5 Casting of cubes and cylinders

The mix ratio of cement: sand: coarse aggregate is 1:0.76:1.8 with water/ binder ratio

as 0.3. The mix proportion was arrived by trial and error method as suggested by Vaishali

(2008). The dosage of superplasticizer is 1% by weight of cement. Total three mixes were

used. First mix with only OPC, second mix with 20 % replacement of Cement with

Metakaolin and third mix was with 20 % replacement of cement with Phosphogypsum.

The cubes were cast in steel moulds of inner dimensions of 150 x 150 x 150mm and

the cylinders were cast in steel moulds of inner dimensions as 150mm diameter and

300mm height.

The cement, sand, coarse aggregate, metakaolin/phosphogypsum were mixed

thoroughly manually. The Super plasticizer is mixed in half of the water required for

74

casting and the specified chemical is mixed in another half water. After that, 50% of

water with chemical was first added, mixed thoroughly and then the water with

superplasticizer is added and mixed. Care has to be taken in mixing to avoid balling

effect. For all test specimens, moulds were kept on floor and the concrete was poured

into the moulds in three layers by tamping with a tamping rod.

Fig. 4.8: View of the Concrete filled in the Moulds

4.3.2.6 Curing

The moulds were removed after 3 days and the specimens were kept immersed

in deionised water mixed with the specified chemical with specified dosage. After

curing the specimens were tested for 7 days, 28 days and 90 days compressive

strength .The specimens were tested for 90 days compressive strength also are cured

for only 28 days. They are kept outside after 28 days till 90 days testing.

4.3.2.7. Cube compressive strength test

The test set up for conducting cube compressive strength test is depicted in

Fig. 4.9. Compression test on the cubes is conducted on the 2000 KN AIMIL - make

digital compression testing machine. The pressure gauge of the machine indicating the

load has a least count of 1 KN. The cube was placed in the compression-testing

75

machine and the load on the cube is applied at a constant rate up to the failure of the

specimen and the ultimate load is noted. The cube compressive strength of the

concrete mix is then computed. This test has been carried out on cube specimens at 7

days, 28 days and 90days age.

Fig. 4.9: Compressive Strength test set up

4.3.2.8 Split tensile strength

This test is conducted on 2000 KN AIMIL make digital compression testing

machine as shown in Fig. 4.10. The cylinders prepared for testing are 150 mm in

diameter and 300 mm long. After noting the weight of the cylinder, diametrical lines

are drawn on the two ends, such that they are in the same axial plane. Then the

cylinder is placed on the bottom compression plate of the testing machine and is

aligned such that the lines marked on the ends of the specimen are vertical. Then the

top compression plate is brought into contact at the top of the cylinder. The load is

applied at uniform rate, until the cylinder fails and the load is recorded. From this

76

load, the splitting tensile strength is calculated for each specimen. In the present work,

this test has been conducted on cylinder specimens after 7 days, 28 days and 90 days.

Fig.4.10: Split tensile strength test set up

4.3.2.9 Powdered X-ray diffraction studies

Powered X-ray diffraction (XRD) is one of the most widely used and useful

technique for investigation of both quantitative and qualitative phase analysis and

provides information regarding specific components. In the powder diffraction

analysis information relating to the structure of the substance and its allotropic

transformation, transition to different phases and the purity of the substances are

obtained. The samples under investigation for the XRD were grounded well to a fine

powder and a flat specimen was prepared on a glass substrate with each sample using

adhesive material. The specimen was placed on the Gonio-meter and diffracted

77

intensities (peaks) were recorded with powder diffractometer using monochromatic

copper Kα radiation. X-ray diffraction analysis for concrete samples was carried out

at College of chemical technology, Osmania University, Hyderabad.

Fig.4.11: XRD testing machine

4.3.2.10 Scanning electron microscopy (SEM)

The concrete samples were broken in to samples, coated with nickel and

examined under the scanning electron microscope and SEM photographs were taken.

SEM analysis for concrete samples was carried out at College of Chemical

Technology, Osmania University, Hyderabad.

78

Fig.4.12: SEM testing machine

4.4. CLOSURE

Various tests on raw materials viz. cement, fine aggregate, coarse aggregate,

metakaolin and phosphogypsum have been conducted to confirm their suitability for

use in concrete making as per the procedures as in I.S.codes. It is observed that all the

materials satisfy the relevant provisions of Indian Standard code of practice. The

results of various tests are presented in this chapter.

A total of 288 samples were cast and tested for initial setting time and 288

samples for final setting time experiments were casted and tested. A total of 432

samples of concrete were used in compaction factor test and 432 samples of concrete

were used in vee-bee time test. A total of 1296 concrete cubes casted and were tested

at 7, 28 and 90 days for compressive strength. The same number of cylindrical

samples were tested for split tensile strength test at 7, 28 and 90 days. The details of

the experimentation have been presented in this chapter. In the next chapter the details

of experimental investigation and a useful discussion of test results will be presented.