CHAPTER – 4

MATERIALS AND EXPERIMENTATION

4.1 GENERAL

The physico-chemical properties of cement, fly ash based blended cement, coarse aggregate, fine

aggregate and water used in the investigation are presented in this chapter. The standard experimental

procedures laid down in IS codes, which were adopted for the determination of normal consistency, initial

and final setting times, compressive strength and chloride ion permeability of concrete cubes and

cylinders are also presented in this chapter. X-ray diffraction analysis was carried out according to the

procedure described in the instruction manual of the X-ray diffractometer.

4.2 MATERIALS

The materials used in the experimental investigation include.

1. Fly ash based blended cement

2. Coarse aggregate

3. Fine aggregate

4. Silica Fume

5. Fibre

6. Water

7. NaCl, KCl, Na2SO4, CaCO3, CaCl2, MgCl2, MgSO4, Mg (HCO3)2, HCl, H2SO4, Na2CO3 and

NaHCO3 with different concentrations in mixing water.

The properties of these materials are given in the following sub-sections.

4.2.1 Cement

Initial experiments like initial setting time, final setting time, soundness and compressive strength

test on mortar cubes were conducted on Portland Pozzolana Cement (PPC)(being referred as Blended

Cement in the present study) conforming to IS 1489-1991 (Part I). The chemical and physical

composition of Blended Cement (Fly ash based) was supplied by the manufacturing company. The results

of the analysis of the cement are presented in Table 4.1 and 4.2 respectively.

Table 4.1 Chemical composition of blended cement (Fly ash based)

Sl.No Parameter Result

1. Insoluble Material (% by mass) 18.90

2. Magnesia (% by mass) 0.99

3. Sulphuric Anhydride (% by

mass) 2.67

4. Loss on Ignition (% by mass) 2.04

5. Total Chlorides (% by mass) 0.001

Table 4.2 Physical properties

Sl.No Parameter Result

1 Fineness (m2/kg) 315

2 Standard Consistency (%) 27.5

3 Setting Time (minutes)

a.Initial

b.Final

230

320

4 Soundness

a.Le-Chat Expansion (mm)

b.Autoclave Expansion (%)

1.30

0.040

5 % of Fly Ash addition 30.0

4.2.2 Coarse aggregate

Crushed Granite stone aggregate of maximum size 20 mm, confirming to IS 383-1970 was used.

The specific gravity and fineness modulus were found to be 2.622 and 7.08 respectively. Grading analysis

is presented in Table 4.3.

Table 4.3 Grading analysis for coarse aggregate

Sl. No I.S. Sieve size Weight

Retained

(gms)

Cumulative

weight retained

(gms)

Cumulative %

retained

%

passing

1 80 mm - - - 100.00

2 40 mm - - - 100.00

3 20 mm 600.00 600.00 12 88.00

4 10 mm 4200.00 4800.00 96 4.00

6 4.75 mm 200.00 5000.00 100.00 -

7 2.36 mm - - 100.00 -

8 1.18 mm - - 100.00 -

9 600 microns - - 100.00 -

10 300 microns - - 100.00 -

11 150 microns - - 100.00 -

Total 5000.00 708.00

Fineness Modulus=708.00/100 = 7.08

4.2.3 Fine aggregate

The fine aggregate (sand) used throughout the experimental work was obtained from the river

Pandameru near Anantapur (Andhra Pradesh). According to IS 650-1996, the sand used in cement mortar

should conform to the following specifications.

i. Sand shall be of quartz, light gray or whitish variety.

ii. It shall be free from silt.

iii. The grains shall be angular. The shape of grains shall approximate to spherical form; enlarged

and flattened grains shall be present only in negligible quantities.

iv. Grading

Passing through 2mm I.S.Sieve 100%

Retained on 90 I.S. Sieve 100%

Particle size greater than 1mm 33.33%

Particle size smaller than 1mm

and greater than 500 33.33%

Particle size smaller than 500 33.33%

v. Sand shall be free from organic impurities Loss of weight on interaction with hot hydrochloric

acid (specific gravity 1.16) shall not exceed 0.25%.

The specific particle size composition of the sand was prepared as per the I.S.Code 650-1966 and I.S.

Code 383-1970. Sand was thoroughly washed with tap water to remove impurities like decayed vegetable

matter, humus, organic matter and deleterious materials like clay, fine silt and fine dust and was oven

dried for 24 hours and cooled to room temperature. This sand was used for the experimental work.

The properties of sand were analysed in accordance with the procedures laid down in I.S 2386

(Part I & Part III) – 1963 and are presented in Table 4.4 and 4.5.

Table 4.4 Properties of sand

Sl. No Property Unit Result

1 Specific Gravity --- 2.75

2 Bulk Density KN/m3 15.54

3 Fineness Modulus --- 2.80

4 Particle size variation mm 0.09 – 2.0

5 Loss of weight with

concentrated Hydrochloric acid

% 0.124

Table 4.5 Grading analysis for fine aggregate

Sl.

NO

I.S. Sieve

size

Weight retained

(gms)

Cumulative

weight retained

(gms)

Cumulative

% retained

% passing

1 80 mm - - - 100.00

2 40 mm - - - 100.00

3 20 mm - - - 100.00

4 10 mm - - - 100.00

5 4.75 mm 9.00 9.00 0.90 99.10

6 2.36 mm 37.00 46.00 4.60 95.40

7 1.18 mm 220.00 266.00 26.60 73.40

8 600 microns 350.00 616.00 61.60 33.40

9 300 microns 247.00 863.00 86.30 7.80

10 150 microns 137.00 1000.00 100.00 0.00

Total 1000.00 280.90

Fineness Modulus = 280.00/100 = 2.80.

4.2.4 Silica Fume

Silica fume was purchased from M/s Elikem Metallurgy P. Ltd., Mumbai for the present

investigation. Chemical composition of silica fume is presented in Table 4.6. In the present experimental

investigation, 5% of silica fume has been added to the readily available Portland Pozzolana Cement.

IS:1489-1991(Part 1) stipulates a range of pozzolana content as 15 -35 %. The Portland Pozzolana

Cement, used for the study, consisted 30% of fly ash. In order to have a cap on pozzolana material in the

cement, 5% of silica fume was added in BCC.

Table 4.6 Characteristics of Silica Fume

S.No Constituent Percent content

1 SiO2 95.65

2 Al2 O3 0.23

3 Fe2O3 0.07

4 CaO 0.31

5 MgO 0.04

6 S O3 0.17

7 Na2O 0.15

8 K2O 0.56

9 LOI 2.27

10 Specific surface area m2/g 16.7

4.2.5 Water

Deionised water has been used for mixing as well as curing of concrete for control specimens 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 4.7.

Table 4.7 The Characteristics of deionised water

Sl. No Parameter Amount

1 pH 7.0

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) 0.30

7 Chlorides (mg/l) 9

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 concretes. Various materials used for investigation are depicted in Figure 4.1.

Fig. 4.1 View of materials

4.2.6 Fibre

Crimped Steel fibres have been used in the present investigation in production of Fibre

Reinforced Concrete (being referred as Steel Fibre Reinforced Blended Cement Concrete (SFRBCC) in

the present study). The said fibres were purchased from Stewols India (P) Ltd., Nagpur, India. Properties

of the used steel crimped fibres, as supplied by the company, are listed out in the Tab.4.8. A pictorial

view of the crimped fibres used is presented in Fig.4.2

Table 4.8. Properties of Rounded Crimped Steel Fiber

S.No

Parameter

Value

1 Equivalent Diameter, mm 1.00

2 Specific Gravity, kg/m

3 7840

3 Tensile Strength, Mpa 345

4 Young’s Modulus. Gpa 200

5 Ultimate Elongation, % 5

6 Aspect Ratio 50

Fig.4.2. View of steel crimped fibres

4.2.7 Chemical Substances

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

compound substances were further categorized into four major divisions viz., i) Neutral salts ii) Slightly

acidic substances iii) Strong acids and iv) Strong alkaline substances. Table 4.9 gives the list of chemical

substances along with the range of concentrations and pH values.

Table 4.9 Classification and details of chemical substances

Sl. No Name & Symbol Range of Concentration Range of pH

1 Neutral salts

a) NaCl

b) KCl

c) Na2SO4

d) CaCO3

0.5-20 g/l

0.5-14 g/l

1.0-20 g/l

0.025-0.3 g/l

7.0-7.01

7.0-7.05

7.0-7.04

6.9-7.1

2 Slightly Acidic substances

a) CaCl2

b) MgCl2

c) MgSO4

d) Mg(HCO3)2

0.2-2 g/l

0.2-2 g/l

0.1-2 g/l

0.1-0.6 g/l

7.2-6.2

7.01-6.8

7.10-6.13

7.04-6.90

3 Strong Acids

a) HCl

b) H2SO4

100-900 mg/l

100-900 mg/l

4.3-6.03

4.3-6.03

4 Strong Alkaline substances

a) Na2CO3

b) NaHCO3

1.0-15 g/l

1.0-15 g/l

8.3-11.20

7.6-9.7

4.3 FABRICATION AND CASTING

The specimens for setting time of cement were cast in Vicat mould of a split ring 80 mm in

diameter and 40 mm in height and rests on a non-porous plate. For preparing one sample, 400 gm of

cement passing 850-micron IS sieve is taken and prepared a paste of cement by gauging the cement with

0.85 times the water required for standard consistency. Then the Vicat mould resting upon non-porous

plate is filled with the with the cement paste. After completely filling the mould, the top surface is

smoothened off by single movement of palm. Then the mould is slightly shaken to expel air.

The cubes were cast in steel moulds with inner dimensions of 150x150x150 mm.

The mix used for casting the cubes of Portland Pozzolana Cement Concrete (BCC) is as per the

proportions obtained in the mix design carried out according to the procedure prescribed in IS 10262-

1982. The details of the mix design are presented in Appendix-A.

In case of casting the cubes of Silica Fume Blended Cement Concrete, the silica fume was added

to blended cement (BC) by 5%. While casting the SFRBC Concrete cubes, 1% of steel crimped fibres

were added to Blended Cement Concrete (BCC).

4.3.1 Curing of specimens

The cube specimens from the moulds were removed after 24 hrs and they were kept immersed in

the corresponding curing ponds for curing. The curing ponds consists the same concentration of chemical

substance in the water, which was used for mixing the concrete. The specimens were cured for 28 days

for 28-day strength and 90 days for 90-day strength. The specimens were removed from the curing ponds

after the required period and allowed to dry under shade.

4.4 EXPERIMENTATION

The experimental methods adopted were in accordance with the standard procedures in Bureau of

Indian Standards (BIS). They are briefly presented in the following sub-sections.

4.4.1 Test Programme

The details of the specimens used in the experimental work are presented in Table 4.10. A total of

444 samples of standard moulds used in Vicat’s apparatus were cast and tested for initial and final setting

time experiments. A total of 1332 concrete cubes of (15x15 cm) 225 cm2 cross-sectional area were tested

at 28 days and 90 days for compressive strength. A total of 666 samples were prepared and tested for

chloride ion permeability.

Table 4.10. Details of test Programme

Sl.

No

.

Chemical

constituent

Conc No. of

Specimens

for Setting

times

No. of Specimens for

compression test

No. of

Specimens

for RCPT

Total

I Deionised

Water

(Control)

---- 3 3 3×2 3×2 3×2

II Chemical

spiked

water

a)Neutral

salts

i)NaCl (g/l)

0.5

2.0

4.0

6.0

8.0

10.0

12.0

14.0

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33

33

33

16.0

20.0

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

33

33

ii)KCl

(g/l) 0.5

2.0

4.0

6.0

8.0

10.0

12.0

14.0

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33

33

33

iii)Na2SO4

(g/l)

1.0

2.0

4.0

10.0

15.0

20.0

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33

iv)CaCO3

(g/l) 0.025

0.075

0.1

0.2

0.3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2 3×2

3×2

3×2

3×2

3×2 3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

Sl.

No

.

Chemical

constituent

Conc No. of

Specimens

for Setting

times test

No. of Specimens

for compression test

No. of

Specimens for

RCPT

Total

b)Slightly

Acidic

substances

i) CaCl2

(g/l)

0.2

0.5

1.0

1.5

2.0

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2 3×2

3×2

3×2

3×2

3×2 3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

ii) MgCl2

(g/l) 0.2

0.5

1.0

1.5

2.0

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2 3×2

3×2

3×2

3×2

3×2 3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

iii) MgSO4

(g/l)

0.1

0.2

0.5

0.75

1.0

1.5

2.0

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33

33

iv)Mg(HC

O3)2 (g/l)

0.1

0.2

0.3

0.4

0.5

0.6

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33

c)Strong

Acids

i)HCl

(mg/l)

100.0

150.0

300.0

500.0

900.0

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

ii)H2SO4

(mg/l)

100.0

150.0

300.0

500.0

900.0

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

Sl.

No

Chemical

constituent Conc

No. of

Specimens

for Setting

times test

No. of Specimens for

compression test

No. of

Specimens for

RCPT

Total

d)Strong

Alkaline

substances

i)Na2CO3

(g/l)

1.0

2.0

4.0

6.0

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

10.0

15.0

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

33

33

ii)NaHCO3

(g/l)

1.0

2.0

4.0

6.0

10.0

15.0

3

3

3

3

3

3

3

3

3

3

3

3

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3×2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

33

33

33

33

33

33 Total 222 222 444 444 444 222 222 222 2442

4.4.2 Experimental Procedure

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

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

penetration of a needle under a total load of 300 gm. The initial set is an arbitrary time in the setting

process, which is reached when the needle is no longer able to pierce the 40 mm deep pat of the cement

paste to 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 conforming to IS 5513 – 1976 consists of a frame to which a movable rod

having an indicator is attached which gives the penetration. The rod weights 300 gm and has diameter and

length of 10 mm and 50mm 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 sub-sections.

4.4.2.1 Consistency

About 300 gm 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 smoothened and leveled. A square needle of size 1

mm x 1 mm 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; if the time taken to complete the experiment exceeds 5 minutes, the sample was rejected

and fresh sample was taken and the operation was repeated again. Fresh cement was taken for each

repetition of the experiment. The plunger was cleaned each time the experiment is done.

4.4.2.2 Initial and Final Setting Times

Cement paste was prepared by gauging cement with 0.85 times appropriate mixing water required

to give a paste of standard consistency. The stopwatch was started at the instant the mixing water was

added to the cement. After half-a-minute, the paste was thoroughly mixed with fingers for one minute.

The mould resting on a nonporous plate was filled completely with cement paste and the surface of filled

paste was leveled smooth with the top of the mould. The test was conducted at room temperature of 27+2

0C at a relative humidity of 60%. The mould with the cement paste was placed in the Vicat’s apparatus

and the needle was lowered gently to make contact with the test block and was then quickly released. The

needle thus penetrates the test block and the reading on the graduated scale of Vicat’s apparatus was

recorded. The procedure was repeated until the needle fails to pierce the block by about 5 mm measured

from the bottom of the mould. The stop button of stop watch was pushed down and the time was recorded

which give the initial setting time. The cement paste was considered finally set when upon applying the

needle gently to the surface of test block, the needle makes an impression, but it fails to penetrate and the

time was noted which gives the final setting time. The needles were cleaned after every repetition and

also care was taken such that there could not be any vibrations.

4.4.2.3 Compressive Strength

Moulds for the cube specimens of size 15 x 15 x 15 cm, are of metal not amenable to attack by

cement concrete and the sides of the mould shall be sufficiently thick, to prevent spreading and warping.

The moulds are rigidly constructed in such a manner as to facilitate the removal of the moulded specimen

without damage. The moulds are machined so that when assembled the dimensions and the internal faces

are accurate to the following specifications.

The height of the mould and the distance between opposite faces shall be 148 mm. The angle

between the adjacent interior faces and top and bottom planes of the mould shall be 900. The interior faces

of the moulds are plane surfaces with a permissible variation of 0.03 mm. The base plate is such

dimensions as to support the mould during the filling without leakage.

While assembling the mould, the joints between the halves of the mould were covered with a thin

film of petroleum jelly and a similar coating of petroleum jelly was applied between the contact surfaces

of the bottom of the mould and its base plate in order to ensure that no water escapes during vibration.

The interior faces of the mould were treated with a thin coating of mould oil.

The assembled mould was placed on the table of the vibration machine and firmly held it in

position by means of a suitable clamp. A hopper of suitable size and shape was attached securely at the

top of the mould to facilitate filling and this hopper was not removed until the completion of the vibration

period. A mixture of Portland Pozzolana Cement (BC), coarse aggregate and fine aggregate in the

proportion obtained as per mix design for M 20 grade was mixed dry for Blended Cement Concrete

(BCC). In case of SFBCC, silica fume by 5% weight of cement was added to BC. To produce SFRBCC,

1% of crimped steel fibres were added to BCC. For all three types of concretes, mixing of their various

constituents was carried out using a mechanical mixer corresponding to IS specifications. The

constituents were first poured into the mixer and mixed in dry condition till uniform colour was obtained.

Then spiked water of the calculated amount was added to it and mixing was continued till a uniform and

homogeneous paste was obtained. The temperature of water and that of the test room at the time when the

above operations were being performed was kept at 27 + 2 0C and the relative humidity 60%.

Immediately after mixing the mortar, it was placed in the cube mould and prodded with the rod. The

concrete was prodded 20 times in about 8 seconds to ensure elimination of entrained air and honey

combing. The remaining quantity of concrete was placed in the hopper of the cube mould and prodded

again as specified for the first layer and further compacted by vibration. The period of vibration was

maintained for two minutes at the specified speed of 12,000 + 400 vibrations per minute (Kaushik et al.,

1988).

At the end of the vibration the mould together with the base plate was removed from the machine

and the top surface of the cube was finished smooth with a blade or a trowel. The compacted cubes in the

moulds were maintained at controlled temperature of 27+ 2 0C and at 90 percent relative humidity for 24

hrs by keeping the moulds under wet gunny bags. After 24 hrs., the cubes were removed from the moulds

and immersed in the corresponding mixing water until taken out for testing. Separate concrete curing

ponds used for curing of cubes in the corresponding mixing water.

Three cubes were tested for compressive strength each time in the 200-tonne universal testing

machine at 28 days and 90 days. The periods are being reckoned from the completion of vibration. The

cubes were tested on their sides without any packing between the cube and the steel platens of the testing

machine. One of the platens is carried on a base and it self-adjusting and the load was steadily and

uniformly applied, starting from zero at the rate of 350 kg/cm2/min. Cubes prepared and kept for curing

can be seen in Fig.4.3.

Fig. 4.3 Curing of specimens

4.4.2.4 Powdered X-ray Diffraction Studies

Powder X-ray Diffraction (XRD) is one of the most widely used and useful technique for

investigation of both qualitative and quantitative phase analysis and provides information regarding

specific components. In powder diffraction analysis, information relating to the structure of the substance

and its allotropic transformation, transition to different phases and the purity of the substance 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. Photograph of

powdered material samples is placed as Fig.4.4 below. The specimen was placed into the specified slot

and diffracted intensities (peaks) were recorded with powder diffractometer using monochromatic copper

K radiation.Fig.4.5 shows the Computer aided X-ray Diffractometer manufactured by a Japanese

company namely Rigaku. Company’s make namely MiniFlex is the benchtop XRD system with an

available sample changer.

Fig. 4.4 Samples prepared for X-ray diffraction testing

Fig.4.5 Computer aided MiniFlex benchtop X-ray Diffractometer

4.5. Rapid Chloride Permeability Test Procedure

The equipment consists of variable D.C. Power supply which can feed constant stabilized 0-80

volt to 4 Nos of applied voltage cell. The cells are made up of polymethyl methacrylae as per the

international standards. The cell are connected to the main instrument through 3 pin plug and socket for

the voltage feeding Protective fuses of 2 ampere are also provided for each cells.

In the present study, RCPT was carried out using disc shaped test specimens of nominal size 100

mm diameter x 50 mm thickness. The test set-up consisted of two acrylic plastic chambers having

grooved recesses on one face and closed at the other end. The specimen end faces can snug-fit into the

open faces of the chambers. One of the cells is filled with NaCl solution (concentration 2.4M), while the

other is filled with 0.3M NaOH solution. Copper mesh electrodes are mounted in the cells such that they

are in contact with the end faces of the specimen. The whole assembly is held together by long threaded

rods with wing nuts at both ends. This can be viewed in Fig.4.6.

Fig.4.6 Concrete samples for RCP Test and Apparatus for RCPT

The disc shaped specimen, taken out from the curing chamber, is coated with quick setting cooxy

on its curved faces and water saturated for 72 hours. It is then mounted with acrylic chambers and

assembled. After checking for leak proofness, the chambers are filled with the chloride and hydroxide

solutions as stated earlier. A potential difference of 60V is applied a between the electrodes. The

electrochemical cell, constituted by this assembly, results in the rapid migration of chloride ions from the

sodium chloride solution to the sodium hydroxide solution, via the pore net work offered by the concrete

specimen. The movement of chloride ions is proportional to the intensity of electric current as measured

by an ammeter in the power source. The test is carried out for duration of 6 hours and the current is

measured at one hour intervals. The total charge carried is computed using Simpson's 1/3rd

rule. The test

was earned out at the age of 28 days.

As per classification system adopted by ASTM C-1202, the concrete resistance to chloride

permeability is classified as follows in Tab.4.11.

Table 4.11 Suggested Permeability values for concretes

Charge (Coulombs)

CI Permeability

>4000

High

2000-4000

Moderate

1000-2000

Low

1000-100

Very low

<100

Negligible

4.6 CLOSURE

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

steel fibre and water have been conducted to confirm their suitability for use in concrete making as per the

procedures laid down in I.S. codes. It is observed that all the materials satisfy the relevant provisions of

Indian Standard code of practice. The results of the various tests are presented in this chapter.

A total of 444 samples were casted for initial and final setting time and tested by using Vicat’s

apparatus. A total of 1332 cubes were cast and tested for compressive strength at 28 days and 90 days.

666 specimens were also cast for testing on RCPT to know the chloride ion permeability. The details of

the experimentation have been presented in this chapter. In the next chapter, the results obtained from the

experimental work and detailed analysis, when neutral salts are added to mixing water, is presented.