chapter 4 results and discussion on mechanical properties...

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CHAPTER 4

RESULTS AND DISCUSSION ON MECHANICAL

PROPERTIES OF CONCRETE

4.1 INTRODUCTION

The results obtained from the experimental works are presented and

discussed in this module. The effects of replacing various admixtures (fly ash,

silica fume, rice husk ash, calcium nitrate), while preparing the concrete, on

the important mechanical properties of the concrete such as compressive

strength, split tensile strength, flexural strength of PCC beam, permeability

etc are discussed in detail and compared with the conventional concrete

specimens prepared for M25 and M30 grade of concrete.

4.2 OPTIMIZATION OF THE ADMIXTURES

Several experimental trials were conducted to optimize the quantity

of the admixtures to be added for preparing the concrete starting with 1% to

25% in all the combinations. The following tables represent the various values

obtained during the trial. Among the various trial results, the best result was

obtained for the following combination and they are presented in the

following Tables 4.1 to 4.6 for M25 grade of concrete.

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Table 4.1 Mechanical Properties of the concrete for proportion 1 for

M25 grade of concrete

Name of the

admixtures

added

Admixture

added in

Percentage

Significant Strength Properties after

28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 20.0

34.45 2.81 3.75Silica fume 10.0

Rice husk ash 15.0

Calcium nitrate 3.0

Table 4.2 Durability Properties of the concrete for proportion 1 for


Name of the

admixtures

added

Percentage

of admixture

added

Significant Durability Properties after 28 days

Loss of Weight in percentage

Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 20.0

0.50 0.94 0.59 1.82Silica fume 10.0

Rice husk ash 15.0

Calcium nitrate 3.0

83



Name of the

admixtures

added

Admixture

added in

Percentage

Significant Strength Properties after 28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 20.0

35.1 2.94 3.75Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0



Name of the

admixtures

added

Percentage of

admixture

added

Significant Durability Properties after

28 days Loss of Weight in percentage

Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 20.0

0.52 0.67 0.45 1.17Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0

84



Name of the

admixtures

added

Admixture

added in

Percentage


28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 15.0

34.97 2.89 3.75Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0



Name of the

admixtures

added

Percentage

of admixture

added



Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 15.0

0.49 0.34 0.47 0.75Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0

85

Table 4.7 Mechanical and Durability properties of the conventional

concrete specimen for M25 grade of concrete

Significant Strength Properties

after 28 days



Compr.

Strength MPa

Spl. Ten.

MPa

Fle. Str.

MPa

Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

32.46 2.68 3.75 1.18 1.96 3.11 3.35

Figure 4.1 Strength properties of the concrete for various proportions

for M25 grade of concrete

86

Figure 4.2 Durability properties of the concrete for various proportions


It was observed from the above results and Figure 4.1 and

Figure 4.2, both the strength and durability properties were improved

considerably by the addition of admixture. In which P1 observed the

combination of 20.0% fly ash, 10.0% silica fume, 15.0% rice husk ash and

3.0% calcium nitrate, P2 observed the combination of 20.0% fly ash, 10.0%

silica fume, 10.0% rice husk ash and 3.0% calcium nitrate and P3 observed

the combination of 15.0% fly ash, 10.0% silica fume, 10.0% rice husk ash and

3.0% calcium nitrate and it was also observed that, for the combination of P3

a better result in terms of both the mechanical and durability properties were

obtained comparatively with respect to the conventional concrete specimens

which are presented in the table 4.7. Hence the study was carried out for 28

days, 56 days, 90 days, 120 days and 180 days for M25 grade of concrete.

87

Among the various trial results, the best result was obtained for the

following combination and they are presented below in the following

Tables 4.8 to 4.14 for M30 grade of concrete.



Name of the

admixtures

added

Admixture

added in

Percentage


28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 20.0

34.88 3.59 3.75Silica fume 10.0

Rice husk ash 15.0

Calcium nitrate 3.0



Name of the

admixtures

added

Percentage

of admixture

added

Significant Durability Properties after 28

days Loss of Weight in percentage

Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 20.0

0.61 0.53 1.81 5.32Silica fume 10.0

Rice husk ash 15.0

Calcium nitrate 3.0

88



Name of the

admixtures

added

Admixture

added in

Percentage


28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 20.0

36.02 3.89 4.0Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0



Name of the

admixtures

added

Percentage

of admixture

added



Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 20.0

0.51 0.39 1.54 4.14Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0

89



Name of the

admixtures

added

Admixture

added in

Percentage


28 days

Compr. Str.

MPa

Sp. Ten. Str.

MPa

Fle. Str.

MPa

Fly ash 15.0

35.13 3.78 4.0Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0



Name of the

admixtures

added

Percentage of

admixture

added

Significant Durability Properties after 28 days

Loss of Weight in percentage

Sulphate

Attack

Chloride

Attack

Acid

AttackCorrosion

Fly ash 15.0

0.38 0.30 1.32 3.95Silica fume 10.0

Rice husk ash 10.0

Calcium nitrate 3.0

90

Table 4.14 Mechanical and Durability properties of the conventional

concrete specimen for M30 grade of concrete

Significant Strength Properties

after 28 days



Compr.

Strength MPa

Spl. Ten.

MPa

Fle. Str.

MPa

Sulphate

Attack

Chloride

Attack

Acid

Attack

Corrosion

34.71 3.86 4.00 0.42 0.73 2.20 5.64

Figure 4.3 Strength properties of the concrete for various proportions


91

Figure 4.4 Durability properties of the concrete for various proportions


It was also observed from the above Tables and Figure 4.3 and

Figure 4.4 that, for the combination of 15.0% fly ash, 10.0% silica fume,

10.0% rice husk ash and 3.0% calcium nitrate, a better result in terms of both

the mechanical and durability properties were obtained comparatively with

respect the conventional concrete specimens which are presented in the

Table 4.14. Hence the study was carried out for 28 days, 56 days, 90 days,

120 days and 180 days for M30 grade of concrete.

92

4.3 MEASUREMENT OF WORKABILITY

The tests have been conducted to determine the workability of the

fresh concrete and are discussed in detail in the following headings. The

workability is also compared with that of the conventional concrete.

4.3.1 Slump Test

Slump test is the most commonly used method of measuring

consistency of concrete which can be employed either in laboratory or at site

of work. It is used conveniently as a control test and gives an indication of the

uniformity of the concrete from batch to batch. It is observed that the repeated

batches of the same mix, brought to the same slump, will have the same water

content and water cement ratio, provided the weights of aggregate, cement

admixtures are uniform and aggregate grading is within acceptable limits. The

values for both the M25 and M30 grade of the concrete were presented in the

table 4.15 and the figure 4.5 shows the slump test in progress. In spite of low

water cement ratio for M30 grade of the concrete, a better workability was

observed because the added admixtures acted as plasticizers and fluidify the

concrete mix. The added admixtures got adsorbed on the cement particles.

The adsorption of the charged admixtures on the particles of cement creates

particle to particle repulsive forces which overcome the attractive forces. This

may be due to the addition of the fly ash which had resulted in reduction of

water demand for the desired slump.

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Table 4.15 Slump of the concrete

S. No Grade of

Concrete

Type of concrete Slump in

mm

1. M25 Conventional 81-98

2. M25 Admixture added 72-91

3. M30 conventional 52-82

4. M30 Admixture added 44-75

Figure 4.5 Slump cone test in progress

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4.3.2 Determination of Compaction Factor

The compacting factor test is designed primarily for use in the

laboratory but it can also be used in the field. It is more precise and sensitive

than the slump test and is particularly useful for concrete mixes of very low

workability as it is normally used when concrete is to be compacted by

vibration. Such dry concrete are insensitive to slump test. The values of the

compaction factor for both the M25 and M30 grade of the concrete were

presented in the Table 4.16 and Figure 4.6 depicts the compaction factor test

in progress. When the cement particles were flocculated there was a friction

between particle to particle and floc to floc. Hence the required compaction

factor was obtained for both the grade of concrete.

Table 4.16 Compaction Factor of the concrete

S. No Grade of

Concrete

Type of concrete Compaction

Factor

1. M25 Conventional 0.90

2. M25 Admixture added 0.90

3. M30 conventional 0.90

4. M30 Admixture added 0.90

95

Figure 4.6 Compaction Factor test in progress

4.3.3 Observation for Segregation

Segregation may be defined as the separation of the constituent

materials (coarse aggregate, fine aggregate, water etc) of concrete. A best

concrete is the one in which all the ingredients (cement, coarse aggregate, fine

aggregate, water etc) are properly distributed to make a homogeneous

mixture. If a sample of the concrete exhibits a tendency for separation of the

coarse aggregate from the rest of the ingredients, then that sample is said to be

showing the tendency of segregation. Such a concrete is not only going to be

weak but also a lack of homogeneity is also going to induce all undesirable

96

properties in the hardened concrete. A well made concrete, by considering the

various parameters such as size, grading, shape and surface texture of the

aggregate with optimum quantity of waters makes a cohesive mix. Such type

of concrete will not exhibit any tendency for segregation. Since the

segregation was difficult to measure quantitatively, it was observed at the

time of concreting process (Shetty 2011).

There is no segregation observed in the concrete prepared by using

admixtures. The following Figure 4.7 proved that there was no sign of

segregation in both the M25 and M30 grade of concrete. Since the water

content is limited for both the M25 and M30 grade of concrete, segregation

was significantly reduced.

Figure 4.7 Concrete specimen with no sign of segregation

97

4.3.4 General Observations of the concrete

The concrete produced more heat of hydration at the initial stage of

the preparation of the concrete but the total generation of the heat was less

than that of the normal concrete which may be due to the addition of the silica

fume during the preparation of the concrete.

4.3.5 Determination of Water Absorption

The water absorption of M25 grade of the conventional concrete is

3.30% after 28 days, 2.84% after 56 days, 2.60% after 90 days, 2.54% after

120 days and 2.50% after 180 days. The water absorption of the concrete

prepared by replacing 15.0% fly ash, 10.0% silica fume, 10.0% rice husk ash

and 3.0% calcium nitrate is 2.74% after 28 days, 2.40% after 56 days, 2.12%

after 90 days, 2.08% after 120 days and 1.98% after 180 days.

It is observed that the water absorption of the concrete prepared by

replacing 15.0% fly ash, 10.0% silica fume, 10.0% rice husk ash and 3.0%

calcium nitrate is 0.56%, 0.44%, 0.48%, 0.46% and 0.52% respectively lower

than that of the conventional concrete after 28 days, 56 days, 90 days, 120

days and 180 days of testing which are shown in the Figure 4.8.

98

Figure 4.8 Water Absorption of M25 grade of concrete

The water absorption of M30 grade of the conventional concrete is

3.14% after 28 days, 2.62% after 56 days, 2.42% after 90 days, 2.34% after

120 days and 2.20% after 180 days. The water absorption of the concrete


and 3.0% calcium nitrate is 2.96% after 28 days, 2.28% after 56 days, 2.02%

after 90 days, 1.92% after 120 days and 1.64% after 180 days.

It is observed that the water absorption of the concrete prepared by


calcium nitrate is 0.18%, 0.34%, 0.40%, 0.42% and 0.56% respectively lower


days and 180 days of testing which are shown in the figure 4.9.

99

Figure 4.9 Water Absorption of M30 grade of concrete

It may be concluded that the water absorption was reduced in the

concrete specimen prepared with the addition of the admixtures.

4.4 DISCUSSIONS ON MECHANICAL PROPERTIES OF THE

CONCRETE

4.4.1 Compressive strength of the concrete

The compressive test is the most common test conducted on

hardened concrete, partly because it is an easy test to be performed and partly

because most of the desirable characteristic properties of concrete are

qualitatively related to its compressive strength. Among the various strengths

100

of concrete the determination of compressive strength has received a large

amount of attention because the concrete is primarily meant to withstand

compressive stresses. It is used as a qualitative measure for other properties of

the hardened concrete. Almost in all structural applications the concrete is

employed primarily to resist the compressive stresses. The specimens are cast,

cured and tested as per the standards prescribed for such tests. The

compressive strengths given by different specimens for the same concrete mix

are different and hence average of the three is noted. The CON in the

following graphs represents conventional concrete and ADM represents the

concrete prepared by using admixtures.

The compressive strength of M25 grade of the conventional

concrete is 29.96 MPa after 28 days, 30.86 MPa after 56 days, 32.62 MPa after

90 days, 33.24 MPa after 120 days and 33.36 MPa after 180 days. The

compressive strength of the concrete prepared by replacing 15.0% fly ash,

10.0% silica fume, 10.0% rice husk ash and 3.0% calcium nitrate is 32.07

MPa after 28 days, 32.82 MPa after 56 days, 33.22 MPa after 90 days, 33.91

MPa after 120 days and 34.02 MPa after 180 days.

It is observed that the compressive strength of the concrete


and 3.0% calcium nitrate is 7.04%, 6.35%, 1.84%, 2.02% and 1.98%

respectively higher than that of the conventional concrete after 28 days, 56

days, 90 days, 120 days and 180 days of testing which are shown in the

following Figure 4.6. From the figure 4.10, it was clearly observed that the

compressive strength of the concrete increases gradually with respect to the

age of the concrete. The increase in the strength was mainly due to the

addition of the various admixtures (Alhozaimy et al 2012). Alhozaimy et al

101

(2012) had also observed that there was 5%-7% increase in the compressive

strength of the concrete with the replacement of the cement with the

admixture.

Figure 4.10 Variation of compressive strength with age of M25 grade of

concrete

The compressive strength of M30 grade of the conventional

concrete is 35.71 MPa after 28 days, 36.42 MPa after 56 days, 36.79 MPa after

90 days, 36.91 MPa after 120 days and 37.12 MPa after 180 days. The

compressive strength of the concrete prepared by replacing 15.0% fly ash,

10.0% silica fume, 10.0% rice husk ash and 3.0% calcium nitrate is 36.64

102

MPa after 28 days, 36.97 MPa after 56 days, 37.52 MPa after 90 days, 37.93

MPa after 120 days and 38.12 MPa after 180 days.

It is observed that the compressive strength of the concrete


and 3.0% calcium nitrate is 2.60%, 1.51%, 1.98%, 2.76% and 2.70%

respectively higher than that of the conventional concrete after 28 days, 56

days, 90 days, 120 days and 180 days of testing which are shown in the

Figure 4.11. It was from the graph that the compressive strength of the

concrete with age of the concrete was observed. Since the fly ash was used in

the while preparing the concrete, the strength of the concrete was increased

due to the pozzolanic reactivity (Ghrici et al 2007). Initially there was a little

increase in the compressive strength of the concrete, but it was increased

gradually at latter stage due to the addition of the fly ash (Shetty 2011).

The silica fume also played a major role in the improvement of the

compressive strength of the concrete by being very fine pozzolanic material

and it was also observed by the following persons that there was an increase

in compressive strength of the concrete between 3.0% to 7.5% (Abdullah et al

2004, Ali Behnood and Hasan Ziari 2008, Ali Reza Bagheri et al 2012). The

figure 4.12 presents the the compressive strength test of the concrete in

progress.

103

Figure 4.11 Variation of compressive strength with age of M30 grade of

concrete

Figure 4.12 Failure pattern of cube under compression

104

Based on the above results it was concluded that there was

significant increase in the compressive strength of the M25 and M30 grade of

the concrete prepared by replacing 15.0% fly ash, 10.0% silica fume, 10.0%

rice husk ash and 3.0% calcium nitrate with the cement.

4.4.2 Split tensile strength of the concrete

The tensile stress at which the concrete specimen failure occurs is

known as the tensile strength of the concrete. The tensile strength of cement

and sand mortar is tested to judge the tensile strength of the cement and

concrete by preparing the test specimens by using the concrete. To determine

the tensile strength, briquettes of the standard dimensions of mould are used

and specimens are prepared. This is an indirect test to determine the tensile

strength of the concrete cylindrical specimens. This kind of test has been

devised to have a tensile load on 1 mm2 of cross section. The tensile stresses

may develop in the concrete due to drying shrinkage, rusting of steel

reinforcement bar embedded in the concrete, temperature changes etc., and

hence the knowledge of tensile strength of the concrete is very vital important

to ensure the safety of the concrete structure. In reinforced concrete members,

significant importance is given to the tensile strength of the concrete since

steel reinforcement bars embedded in the concrete are provided to resist all

the tensile forces.

The tensile strength of M25 grade of the conventional concrete is 2.67

MPa after 28 days, 2.69 MPa after 56 days, 2.70 MPa after 90 days, 2.73 MPa

after 120 days and 2.75 MPa after 180 days. The tensile strength of the concrete

prepared by replacing 15.0% fly ash, 10.0% silica fume, 10.0% rice husk ash and

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3.0% calcium nitrate is 2.81 MPa after 28 days, 2.86 MPa after 56 days, 2.88

MPa after 90 days, 2.91 MPaafter 120 days and 2.92 MPa after 180 days.

It is observed that the tensile strength of the concrete prepared by


calcium nitrate is 5.24%, 6.32%, 6.67%, 6.59% and 6.18% respectively higher

than that of the conventional concrete after 28 days, 56 days, 90 days, 120 days

and 180 days of testing which are shown in the figure 4.13. The tensile strength

was increased due to the addition of the fly ash (Gambhir 2009, Konstantin

Kovler and Nicolas Roussel 2011). Konstantin Kovler and Nicolas Roussel

(2011) observed an increase in the tensile strength of the concrete by 2%.

Figure 4.13 Variation of tensile strength with age of M25 grade of

concrete

106

The tensile strength of M30 grade of the conventional concrete is

3.86 MPa after 28 days, 3.92 MPa after 56 days, 4.21 MPa after 90 days, 4.35

MPa after 120 days and 4.63 MPa after 180 days. The tensile strength of the

concrete prepared by replacing 15.0% fly ash, 10.0% silica fume, 10.0% rice

husk ash and 3.0% calcium nitrate is 4.02 MPa after 28 days, 4.21 MPa after

56 days, 4.56 MPa after 90 days, 4.94 MPa after 120 days and 4.97 MPa after

180 days.

It is observed that the tensile strength of the concrete prepared by




days and 180 days of testing which are shown in the Figure 4.14. The

Figure 4.15 shows the split tensile strength test in progress. The increase in

the tensile strength of the concrete prepared by replacing 15.0% fly ash,

10.0% silica fume, 10.0% rice husk ash and 3.0% calcium nitrate was because

of the distinct densification of the concrete. It may be also due to the high

pozzolanic activity which was observed by Frank Collins and Sanjayan

(1999) and Katrin Habel et al (2006).

107

Figure 4.14 Variation of tensile strength with age of M30 grade of

concrete

Figure 4.15 View of the concrete specimen after failure

108

It may be concluded that by the replacement with the admixtures,

tensile strength of the concrete is only marginally increased.

4.4.3 Flexural Strength of the Concrete

In reinforced concrete members, a significant importance and

dependence is placed on the flexural strength of the concrete since steel

reinforcing bars are provided to resist all tensile forces. But it is a well known

fact that concrete is relatively strong in compression and weak in tension. The

estimation of flexural strength of the concrete is essential to estimate the load

at which the concrete members may crack. The flexural strength is thus

determined and used when necessary. Its knowledge is useful in the design of

pavement slabs and airfield runway as flexural tension is critical in these

cases. The results are affected by the various parameters such as casting and

curing process, size of the specimens, moisture conditions, rate of loading,

manner of loading etc.

The flexural strength of M25 grade of the conventional concrete is


MPa after 120 days and 3.75 MPa after 180 days. The flexural strength of the




180 days.

It is observed that the flexural strength of the concrete prepared by



109


days and 180 days of testing which are shown in the figure 4.16.

Figure 4.16 Variation of flexural strength with age of M25 grade of

concrete

The flexural strength of M30 grade of the conventional concrete is


MPa after 120 days and 4.25 MPa after 180 days. The flexural strength of the




180 days.

It is observed that the flexural strength of the concrete prepared by


calcium nitrate is 6.25%, 6.25% 0.00%, 0.00% and 0.00% respectively higher

110


days and 180 days of testing which are shown in the Figure 4.17.

Figure 4.17 Variation of flexural strength with age of M30 grade of

concrete

It was observed that the flexural strength was increased only at the

later stage and it can be inferred that at this ageing, the effect of admixture is

insignificant. The flexure strength was increased due to the dense distribution

of particles and low porosity in the concrete (Ali Khaloo and Majid Afshari

2005). Ali Khaloo and Majid Afshari (2005) reported that there was only a

marginal increase in the flexural strength of the concrete due to the

replacement of the admixtures.

It may be concluded that by the replacement of admixtures, the

flexural strength of the concrete was marginally increased (Fattuhi and

Hughes 1982).

111

4.4.4 Study of Beam Subjected to Pure Bending

This study was initiated to compare the strength of the reinforced

cement concrete beam subjected to pure bending, between the conventional

concrete and concrete prepared by using admixture. The following table

presents the details about the load deflection results of the beam prepared

using conventional concrete. There was only 1.15% change in the value of

ultimate load between 28 days of testing and 180 days of testing. Since the

value of ultimate load is almost same for all the durations of testing. Hence

the result of 180 days testing was presented in the following tables from Table

4.17 to Table 4.20.

The first crack load was at 22 KN and the ultimate load was at

89.60 KN. The beam failed in pure bending. The failure crack pattern was

established before the ultimate load was ascertained.

112

Table 4.17 Load versus deflection values for M25 grade of conventionalconcrete

S. No Load (KN)Deflection in mm

LHS Obs. Mid Span obs. RHS Obs.

1. 0 0 0 0

2. 5 0.05 0.10 0.03

3. 10 0.21 0.34 0.19

4. 15 0.36 0.74 0.34

5. 20 0.49 1.06 0.51

6. 25 0.61 1.37 0.60

7. 30 0.75 1.67 0.76

8. 35 0.86 1.94 0.84

9. 40 0.96 2.26 0.94

10. 45 1.08 2.57 1.09

11. 50 1.20 2.81 1.18

12. 55 1.31 3.05 1.29

13. 60 1.39 3.34 1.38

14. 65 1.55 3.58 1.51

15. 70 1.74 3.95 1.71

16. 75 1.87 4.34 1.81

17. 80 2.03 5.72 2.01

18. 85 2.37 6.50 2.29

19. 89.6 2.87 7.42 2.69

113

Table 4.18 Load versus deflection values for M25 grade of concrete

prepared using admixture


LHS Obs. Mid Span obs. RHS Obs.

1. 0 0 0 0

2. 5 0.02 0.08 0.02

3. 10 0.19 0.32 0.16

4. 15 0.31 0.71 0.31

5. 20 0.42 1.04 0.47

6. 25 0.57 1.31 0.59

7. 30 0.71 1.63 0.74

8. 35 0.82 1.91 0.83

9. 40 0.91 2.22 0.92

10. 45 1.02 2.51 1.00

11. 50 1.12 2.76 1.14

12. 55 1.28 2.91 1.24

13. 60 1.34 3.26 1.35

14. 65 1.51 3.52 1.47

15. 70 1.71 3.88 1.68

16. 75 1.82 4.30 1.78

17. 80 2.01 5.68 2.04

18. 85 2.31 6.41 2.33

19. 90 2.81 7.31 2.72

20. 94.2 2.91 7.44 2.89

114


94.20 KN. The beam failed in pure bending.

Table 4.19 Load versus deflection values for M30 grade of conventional

concrete


LHS Obs. Mid Span obs. RHS Obs.1. 0 0 0 0

2. 5 0.04 0.09 0.02

3. 10 0.20 0.32 0.17

4. 15 0.32 0.75 0.31

5. 20 0.47 1.12 0.55

6. 25 0.60 1.34 0.57

7. 30 0.76 1.65 0.77

8. 35 0.81 1.92 0.86

9. 40 0.92 2.25 0.98

10. 45 1.12 2.51 1.08

11. 50 1.21 2.87 1.18

12. 55 1.36 3.01 1.30

13. 60 1.42 3.28 1.41

14. 65 1.52 3.54 1.46

15. 70 1.71 3.93 1.64

16. 75 1.84 4.27 1.78

17. 80 2.11 5.64 2.02

18. 85 2.34 6.31 2.22

19. 90 2.78 6.69 2.60

20. 95 2.96 7.12 2.88

21. 98.4 3.04 8.11 2.97

115


98.40 KN.

Table 4.20 Load versus deflection values for M30 grade of concrete

prepared by adding admixture


LHS Obs. Mid Span obs. RHS Obs.1. 0 0 0 0

2. 5 0.03 0.07 0.04

3. 10 0.18 0.30 0.16

4. 15 0.30 0.71 0.34

5. 20 0.44 1.09 0.51

6. 25 0.56 1.31 0.59

7. 30 0.71 1.60 0.73

8. 35 0.82 1.90 0.80

9. 40 0.90 2.22 0.92

10. 45 1.09 2.47 1.08

11. 50 1.17 2.80 1.14

12. 55 1.32 2.95 1.29

13. 60 1.39 3.21 1.43

14. 65 1.48 3.51 1.47

15. 70 1.68 3.90 1.69

16. 75 1.81 4.22 1.74

17. 80 2.08 5.61 2.04

18. 85 2.29 6.28 2.24

19. 90 2.71 6.60 2.66

20. 95 2.92 7.08 2.89

21. 100 2.98 8.07 2.92

22. 103.26 3.21 8.56 3.18

116


103.26 KN.

Figure 4.18 Failure pattern of the reinforced cement concrete beam

The Figure 4.18 shows the photograph of the beam test in progress.

It was observed that the deflection at the mid portion was higher than that of

the corner portion. A lesser amount of cracks was observed in the concrete

specimen prepared using the admixtures (Fattuhi and Hughes 1982). From the

results, it was observed that there was no reasonable improvement in the

deflection or strength and hence it was not discussed elaborately.

chapter 4 results and discussion on mechanical properties...

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