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111

CHAPTER 4

MATERIALS AND METHODOLOGY

This chapter deals with the description of various materials used in

the experimentation. Also it describes briefly the methodology adopted

to carry out the different tests as per relevant IS codes.

4.1 4.1 MATERIALS USED

4.1.1 Cement

The cement used in the experimentation was ordinary Portland

cement of 43-grade. The physical properties of the cement are given in

Table 4.1.

Table 4.1 Physical properties of ordinary Portland cement- 43 grade

Properties Results Limits as per IS 8112-1989

Fineness 5.5% 10%

Normal consistency 29%

Specific gravity 3.15

Setting time

Initial Final

105 min < 30 minutes

560 min ≯600 minutes

Soundness Test Le-chat expansion

2 mm 10 mm maximum

Compressive strength 3 days 7 days

28 days

24.50 ≮23 N / mm2.

35.50 ≮33 N / mm2.

44.44 ≮43 N / mm2.

4.1.2 Fine Aggregate

Locally available sand confirming to zone II with specific gravity of

2.6 was used as fine aggregate. The sand used was having a fineness

modulus of 2.92. The sand passing 1.18 mm and retained on 150

micron IS sieve was used. Table 4.2 gives the sieve analysis conducted

for fine aggregate.

112

Table 4.2 Sieve analysis of fine aggregate

IS sieve No. % passing Cumulative % retained

4.75 97.31 2.69

2.36 84.82 15.18

1.18 68.51 31.49

600µ 46.89 53.11

300µ 9.27 90.73

150µ 0.87 99.13

4.1.3 Steel Fibers

NOVOCON ISF1050 steel fibers were used in the experimental work.

These fibers are designed especially for the reinforcement concrete,

mortar and other cementitious matrix. The steel fibers of aspect ratio

25, 38 and 50 were used. Thickness of steel fiber was found to be

1mm. The tensile strength of steel fiber was found to be 1100 N/mm2.

The steel fibers of different aspect ratios are shown in plate 4.1, 4.2

and 4.3.

Plate Error! No text of specified style in

document. Steel fibers

of aspect ratio 38


document. Steel fibers

of aspect ratio 25

113

4.1.4 GI Fibers

GI fibers were obtained by cutting locally available GI wire. The

diameter of GI fiber was 1 mm. The aspect ratios adopted for the

experimentation were 25, 38 and 50. The tensile strength of GI fiber is

300 – 500 N/mm2. GI fibers of different aspect ratio are shown in plate

4.4, 4.5 and 4.6.


document. GI fibers of aspect ratio 38 Plate Error! No text of specified style in

document. GI fibers of aspect ratio 25

Plate Error! No text of specified

style in document. Steel fibers

of aspect ratio 50

114

4.1.5 Polypropylene Fibers

Polypropylene fibrillated harbourite fibers of aspect ratio of 800 and

1600 were used in the experimentation. The specific gravity was found

to be 0.91 and tensile strength of polypropylene fibers is 600 N /mm2.

Plate 4.7 and 4,8 show the polypropylene fibers of aspect ratio of 800

and 1600.

The properties of different fibers used are given in table 4.3. Table 4.3 Properties of different fibers used

Fiber type Length (mm)

Thickness / Diameter

Aspect ratio

Specific gravity


document. Polypropylene fibres

of aspect ratio 1600


document. Polypropylene fibres

of aspect ratio 800


document. GI fibers of aspect ratio 50

Steel fiber

25

38

50

GI fiber

25

38

50

Polypropylene fiber

6

12

4.1.6 Welded Mesh

Welded mesh of 12 G with 25 mm x 25 mm square opening was

used. The tensile strength of welded mesh is 1122 N/mm

shows the welded mesh used in the

4.1.7 Chicken Mesh

Chicken mesh of 20G with diamond opening was used.

shows the chicken mesh used in the experimentation.

Plate

Plate

115

1 mm 25 7.80

1 mm 38 7.80

1 mm 50 7.80

1 mm 25 7.70

1 mm 38 7.70

1 mm 50 7.70

7.5 µm 800 0.9

7.5 µm 1600 0.9


The tensile strength of welded mesh is 1122 N/mm

shows the welded mesh used in the experimentation.

Chicken Mesh

Chicken mesh of 20G with diamond opening was used.

shows the chicken mesh used in the experimentation.


document.Chicken mesh


document.Welded mesh

7.80

7.80

7.80

7.70

7.70

7.70

0.9

0.9


The tensile strength of welded mesh is 1122 N/mm2.Plate 4.9

Chicken mesh of 20G with diamond opening was used. Plate 4.10

116

4.1.8 Water

Ordinary potable water which is free from all the impurities such as

organic content, turbidity was used for mixing and curing of the

specimens.

4.1.9 Superplasticizer

To impart the additional desired properties and workability, a

superplasticizer Conplast SP 430 was used. The dosage of the

superplasticizer adopted throughout the experimentation was 1% by

weight of cement. Conplast SP 430 which is a sulphonated

naphthalene formaldehyde condensate is manufactured by Fosroc

chemicals (India) Pvt. Ltd., Bangalore. Conplast SP-430 is a brown

liquid, non-toxic and non-flammable liquid having shelf life of 12

months.

4.1.10 Air-Entraining Admixture

Air entrainment admixture Conplast AEA increases the resistance of

concrete to attack by frost and de-icing salts, reducing the problems of

surface scaling. It also assists in the formation of a stable cohesive

mix, reducing segregation and bleeding. Air entrainment admixture is

a translucent coloured liquid having specific gravity of 1.01 at 27°C,

pH of 7, which is manufactured by Fosroc Chemicals (India) Pvt. Ltd.,

Bangalore.

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4.1.11 Accelerator

The Conplast NC accelerator which is manufactured by Fosroc

chemicals (India) Pvt. Ltd., Bangalore is non-flammable liquid having

shelf life of 12 months was used in the research work.

4.1.12 Retarder

The retarder used in the experiment was Conplast RP264. Conplast

RP264 is a dark brown liquid based on selected lignosulphonates,

specific gravity ranging between 1.170 – 1.190 at 27°C, and is

manufactured by Fosroc chemicals (India) Pvt. Ltd., Bangalore. It is

non-flammable liquid having shelf life of 12 months.

4.1.13 Waterproofing Compound

The waterproof compound used in the experiment was Conplast

X421IC. Conplast X421IC is a dark brown liquid based on

lignosulphonates which is manufactured by Fosroc chemicals (India)

Pvt. Ltd., Bangalore having shelf life of 12 months.

4.1.14 Flyash

Flyash is a by-product of the combustion of pulverized coal in

electric power generating plants and is obtained from Raichur Thermal

Power Plant. The physical and chemical properties of flyash are shown

in Table4.4 and Table4.5.

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Table 4.4 Physical properties of flyash

Density 2.17g/cm3

Bulk density 1.26g/c.c

Moisture content 2%


Fineness 16%

Table 4.5 Chemical properties of flyash

Component IS: 3812-1981 Specifications

Flyash

SiO2 + Al2O3 + Fe2O3 70 minimum 99 – 99.1

SiO2 (alone) 35 minimum 58.8 – 59.1

MgO 5.0 max 0.22 – 0.34

Total sulphur SO3 2.75 max

Alkalis as Na2O 1.5 max 0.54

Loss on ignition 12 max 1.05 – 1.08

CaO - 0.86 – 1.02

K2O - 0.05 – 0.71

% on 45 µ sieve 34* 33

Lime activity at 7 days, MPa

4.25 4.10

Pozzolonic activity index at 28 days, % of control

75* 87

4.1.15 Silicafume

The silicafume used in this investigation is ELKEM Micro-silica

which is a by-product of the manufacture of silicon and ferrosilicon

alloys. This is amorphous and highly reactive. The physical and

chemical properties of silicafume are shown in Table4.6 and Table 4.7.

Table 4.6 Physical properties of silicafume

Particle size < 1µm

Bulk density 130 – 430 kg/m3


Specific surface 15000 to 30000 m3/kg

Table 4.7 Chemical properties of silicafume

SiO2 93.70%

Moisture content 0.60%

L.O.I 1.07

Carbon 0.52%

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4.1.16 Metakaolin

MetaCem is a grade name of Calcined chinaclay manufactured from

20 Microns Limited, Thirunvelli, Tamilnadu. Physical and chemical

properties of metakaolin are as shown in Table 4.8 and Table 4.9.

Table4.8 Physical properties of metakaolin

Average particle size, µ m 1.5

Residue 325 Mesh (% max) 0.5

B.E.T. Surface Area m2/gm 15

Pozzolan Reactivity in mg Ca(OH)2/gm 1050


Bulk density (gm/ltr) 300 ± 30

Brightness 80 ± 2

Physical form Off-white powder

Table4.9 Chemical properties of metakaolin

Chemical Composition Wt

Si02+Al2O3+Fe2O3 96.88%

Cao 0.39%

MgO 0.08%

TiO2 1.35%

Na2O 0.56%

K2O 0.06%

Li2O Nil

L.O.I 0.68%

4.2 CASTING OF SPECIMENS

Cages were prepared by tying the chicken mesh layer to welded

mesh at regular intervals by using binding wire. The prepared cages

were placed in the moulds which were oiled. Cement –sand slurry was

prepared with a mix proportion of 1:1 with a w /c ratio of 0.45, and a

superplasticizer dosage of 1% (by weight of cement). For steel and GI

fibers , initially a small quantity of slurry (10 mm) was poured into the

mould and then the fibers were placed in the mould and then the

slurry was infiltrated upto the brim level and was lightly compacted

using the table vibrator. Whereas for polypropylene fibers, fibers were

120

initially dispersed in the dry cement-sand mortar and then water of

required amount was added, and then the slurry was filled into the

mould and then lightly compacted. Then the moulds were covered with

wet gunny bags for 12 hours. After 12 hours, the specimens were

demoulded and kept in water for 28 days curing. For compressive

strength, specimens of dimensions 150 x 150 x 150 mm were cast. For

flexural strength, specimens of dimensions 100 x 100 x 500 mm were

cast. For impact strength, specimens of diameter 152 mm and

thickness 63.5 mm were cast.

4.3 TESTING OF SPECIMENS

4.3.1 Compressive Strength Test

The compressive strength test was conducted after 28 days of

curing. The compressive strength can be calculated in accordance with

IS 521-1959 using the formula

fc = P / A

Plate Error! No text of specified style in document.Cage for (a)

compressive strength,(b) flexural strength (c) impact strength specimens

(a)

(b)

(c)

121

Where fc - compressive strength of concrete

P – maximum load applied to the specimen

A – cross-sectional area of the specimen

4.3.2 Flexural Strength Test

Flexural strength also termed as modulus of rupture is a measure of

its ability to resist bending. The specimens casted for flexural strength

test were of dimensions 100 x 100 x 500 mm. The effective span was

400 mm and the specimens were subjected to two point loading, the

distance between the loads was 133 mm. The test procedure was

carried out in accordance with IS 516-1959.

The flexural strength of the specimen shall be expressed as the

modulus of rupture and shall be calculated using the formula

fcf = P x L / b d2

Where fcf – flexural strength

P – maximum load applied to the specimen

L – c/c distance between the two supports

b – width of the specimen

d – depth of the specimen


document.Failure of compression specimen

122

4.3.3 Toughness

The toughness is measured by using the load deflection curve. The

toughness index, If is given by

Area under load-deflection curve until the load reaches zero for fiber composite

If = -------------------------------------------------------------------------------- Area under load–deflection curve until the load reaches zero for plain matrix

In the ASTM procedure, the denominator in the above equation is

taken as the area under the load-deflection curve upto the first crack.

The first crack is assumed to occur at the point where the load

deflection curve deviates from the initial linear portion. The numerator

is taken as the area under the load deflection curve upto a certain

specified deflection. Three levels of deflection namely, 3δ, 5.5δ and

10.5δ are suggested for the numerator. The term δ is the deflection

upto 1st crack. Thus

Area under the load deflection curve upto 3δ

I5 = -------------------------------------------------------

Area under the load deflection upto δ

Area under the load deflection curve upto 5.5δ

I10 = ----------------------------------------------------------

Area under the load deflection upto δ

Plate Error! No text of specified style in document.Failure of flexural specimen

123

4.3.4 Impact Strength – Drop Weight Test

Impact strength of concrete is a measure of the ability to absorb the

shock or sudden impact due to external load. The impact strength can

be expressed in terms of energy required to cause crack and is

expressed in terms of N-m.

The impact test specimens were of size 152 mm in diameter and

63.5 mm thick and are subjected to repeated loads (blows) by

dropping a 4.5 kg hammer from a height of 457 mm. Number of blows

required to cause first visible crack is noted as the first crack strength.

Plate Error! No text of specified style in Failure of impact specimens


document.Impact test components

Plate Error! No text of specified style in document.Impact test setup

124

The loading is continued until the specimen fails and opens up such

that it touches three of the four positioning lugs. The Number of blows

required to cause this condition is recorded as the final failure. The

impact strength was calculated as follows

Impact energy = mghN

= w/g * g *h *N

= whN (N-m)

Where m – mass of the ball

w – weight of the ball in N

g – acceleration due to gravity

h – height of drop in m

N – average number of blows to cause failure

4.3.5 Freezing and Thawing Test

After 28 days of curing, the specimens were surface dried and then

they were kept in freezer at a temperature of -14°C for 24 hours. After

24 hours of freezing, the specimens were taken out and kept in open

atmosphere for 24 hours. This completes one cycle of freezing and

thawing. The specimens were subjected to such 90 cycles of freezing

and thawing. After 90 cycles, the specimens were surface dried, and

were tested for their respective strengths.

Plate Error! No text of specified style in document.Specimens

subjected to freezing

125

4.3.6 Temperature Test

After 28 days of curing, the specimens were surface dried. The

specimens were placed in the oven for 4 hours at a sustained

temperature of 100°C. After 4 hours, the oven was switched off and

the specimens were allowed to cool in the oven for few hours. Once the

specimens were cooled, the specimens were taken out. The same

procedure was done for the specimens for 200°C and 300°C. After

subjecting the specimens for the sustained elevated temperature, the

specimens were tested for their respective strengths.

4.3.7 Alternate Wetting and Drying Test

After 28 days of curing, the specimens were surface dried. The

specimens were kept in open atmosphere for 24 hours. After 24 hours

of drying, the specimens are placed in water for 24 hours. This

completes one cycle of alternate wetting and drying. After 90 such

cycles the specimens were surface dried and tested for their respective

strengths.

Plate Error! No text of specified style in document.Specimens

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