effects on properties of m25 grade concrete mix using ... · jetir1805634 journal of emerging...

© 2018 JETIR May 2018, Volume 5, Issue 5 www.jetir.org (ISSN-2349-5162)

JETIR1805634 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 196

Effects on Properties of M25 grade concrete mix

using retarding super plasticizer

1Mohammad Zakir, 2Shaief Manzoor, 3Sumair Javeed 1Ph.d Schoolar ,2 MTech Student 3Mtech Student

1 Department of Structrual Engineering NIT Srinagar, 1Srinagar, India

2Department of Civil Engineering,Alfalah Unversity, 2Faridabad Haryana, India

3Department of Civil Engineering,Alfalah Unversity, 3Faridabad Haryana, India

ABSTRACT

For fresh concrete increase in temperature results in increased water demand, lesser setting time, more slump

loss and less strength.When the time gap between mixing and casting is large Superplasticizers (SP) and

retarders are used to enhance the workability and setting time of concrete to overcome limitations faced.By

using superplasticizers it is possible to make concrete at the lowest possible water/cement ratio while

maintaining a high workability. They have indeed added a new dimension to the application of admixtures

with regards to production of high strength and flowing concretes.

In this study the optimum quantity of admixtures was determined up to limit the desired

parameters are improved without having any undesirable effects on mechanical properties (such as

Compressive strength, flexural strength and tensile strength) of concrete. Hence an experimental investigation

is to be conducted to determine the optimum dosage for the admixtures and to study the effect of over dosage

of super plasticizer and retarder. After casting, normal curing is to be carried out on the concrete samples until

the 28th

day.

The quantity of SP and retarder dosages of 0.3%, 0.5%, 0.8%,1%, and 1.5%

by weight of cement were used, together with control mix (w/c ratio = 0.40). After casting, normal curing

was carried out on the concrete samples till the 28th

day. Properties such as compressive strength, tensile

strength and flexural strength was determined on 3rd

, 7th

, and 28th

days of curing, besides determining the

workability of the fresh concrete by slump and compaction factor tests.In this study also the comparison was

made between the properties of control mix and the varying percentage of admixture mixes and optimum

dosage of the admixture is determined for constant w/c ratio. The comparison was then made with the

properties of concrete of lower water cement ratio of 0.38,0.35 and 0.33 and quantity of the admixture is

determined which can offset the decrease in workability of concrete due to lower w/c ratio.

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Indexwords

Properties of Concrete,M25 Grade, Superplasticizer

INTRODUCTION The restrictions and harmful effects on concrete can be overcomed by using retarders which decrease setting

times during circumstances when delays between mixing and placing occur. The accelerating effects of hot

weather on the setting times of concrete or delay the initial set of concrete can be avoided by using retarders

or when difficulty or unusual conditions of placement occur such as placing concrete in Piers,foundations,oil

wells and mass concreting. Retarding admixture is an admixture that retards the setting of concrete.

The Retarding admixtures have main ingredient as lingo-sulfonic acids and

salts, hydroxyl carboxylic acids and their salts,inorganic salts such as lead salt, borates,zinc, phosphates, sugar

and their derivatives. Retarding effects rely upon a number of factors including quantity of the admixture,

time of addition of the mix and curing conditions.

A mass number of impeding items are accessible that can be utilized as bond set retarders in

concrete mix.Some ordinary hindering admixtures defer the setting time of cement by couple of hours, while

a portion of the propelled items, for example, Dalvocrete keep concrete blends crisp for any coveted

timeframe, up to 3 days

A retarding admixture decreases the process of hydration, leaving more water which makes

concrete to be workable thus ample time is avialable for concrete to be placed, compacted and finished. Thus

without changing the water cement ratio, Superplasticizer is used to get desirable workable mix.Also it is used

to increase the ultimate strength of concrete by reducing water content while keeping the mix workable. This

experimental work is carried out to study the effect of optimum quantity of retarder to be used and Super

plasticizer properties of concrete Sodium lignosulphonate is used as a retarding Superplasticiser to enhance

the various properties of concrete.

SCOPE AND OBJECTIVE The study is aimed to find out the harmful effects of retarding superplasticizers if any on properties of M25

concrete. Also the optimum dosage of admixtures will be determined up to which the desired parameters are

improved without having any bad/harmful effects on mechanical properties (such as Compressive strength,

flexural strength and tensile strength) of concrete.thereby an experimental investigation will be conducted to

determine the optimum quantity of admixtures and to study the effect of over dosage of super plasticizer and

retarder. After casting, normal curing was carried out on the concrete samples until the 28th

day. The aim is

to study optimum dosgage and over-dosage effects of super plasticizers and retarders on compressive strength,

flexural strength, and split tensile strength of concrete mix with age in comparison to controlled concrete and




investigate the harmful effects if any of retarding superplasticizers on the properties of concrete.

Material Requirement

The various materials required for this project work are as:

Cement The cement used in this work is KHYBER 53 grade Ordinary Portland cement. This cement is checked and

tested according to Indian Standard specification (IS 12269: 1987) showing properties conforming to it.

Aggregate

Aggregates used in the project: Graded crushed aggregate 10 and 20 mm from river Jehlum in Srinagar

region is used in this work. The rock type classification of region is Sedimentary. Fine Aggregates: Sand

was used as locally available material. It graded sand zone II according to Indian standard.

Water Ordinary tap water was used in this work for all concrete mixes and curing of specimens. Admixture The admixture used in the current work is a retarding Superplasticiser namely sodium lignosulphonate. The

raw material for production of lignosulphonate is trees. Lignosulphonate, or sulphonated lignin are water-

soluble anionic polyelectrolyte polymers.These are by products formed from the production of wood pulp

using sulfite pulping.The sulfite process produces wood pulp which is pure cellulose fibres by using various

salts of sulphurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The

salts used in the pulping process are either sulphites (SO32−), or bisulphites (HSO3

−) depending upon the PH.

The counter ion can be calcium (Ca2+), sodium (Na+), ammonium(NH4+) or magnesium (Mg2+).

Apparatus and instruments Different apparatus and instruments are required for this project work. Cubical moulds of size 150mm x

150mm x150mm made of steel are used for the determination of compressive strength. Cylindrical steel

moulds of dia 150mm and height 300mm are required for the determination of split tensile strength. Steel

beams of size 100mm x100mm x500mm are required for the determination of flexural strength. Various

instruments such as UTM is used for strength determination. Vicat’s apparatus is used for determining

consistency and initial and final setting times of cement. Compaction factor apparatus is used for the

determination of compaction factor. A pycnometer is used for specific gravity determination of sand and a

wire basket is used for determination of specific gravity of coarse aggregate. A set of sieves is used for

determining the zoning of sand. A table vibrator is also needed for the compaction of concrete moulds

EXPERIMENTAL WORK All the experimental work was conducted successfully in the concrete and the structure labs of the college. In

this work two sets of castings were prepared. One set consisted of mixes prepared at a constant w/c ratio of

0.4, with the varying dosage of the sodium lignosulphonate (0.3, 0.5, 0.8, 1.0, 1.5 %) each time with the

control mixes. The second set consisted of mixes casted at decreasing w/c ratio and the admixture dosage


https://en.wikipedia.org/wiki/Polyelectrolyte

https://en.wikipedia.org/wiki/Calcium

https://en.wikipedia.org/wiki/Ammonium

https://en.wikipedia.org/wiki/Magnesium



required to attain a constant workability.

1 Strength tests based on constant w/c ratio These tests are carried out at a constant w/c ratio of 0.4 with varying dosage of the admixture sodium

lignosulphonate. The various tests carried out at constant water cement ratio include.

1.1Cube Compressive strength The cube compressive strength results at the various ages such as 3, 7, 28 days and at Superplasticiser dosage

of 0.3, 0.5, 0.8, 1.0, 1.5 % at a constant w/c ratio 0f 0.4 are presented in Tables below

Table 1: 3rd day compressive strength results

S. No S.P. dosage 3rd

day compressive Strength(Mpa) %age increase

(%) (3rd

day)

Normal Admixed

1. 0.3 10 10.4 4.00

2. 0.5 10.3 11 6.79

3. 0.8 11.4 13.6 10.46

4. 1.0 11.8 13.2 11.86

5. 1.5 12.3 12.1 - 1.62

Table 2: 7th day compressive strength results

S. No S.P. dosage 7th

day compressive %age increase

(%) Strength(Mpa) (7th

day)

Normal Admixed

1. 0.3 18 18.7 3.88

2. 0.5 18.2 19.4 6.59

3. 0.8 20.2 23.4 15.84

4. 1.0 20.6 22.7 10.19

5. 1.5 21.2 20.8 - 1.88




Table 3: 28th day compressive strength results


day compressive %age increase

(%) Strength(Mpa) (28th

day)

Normal Admixed

1. 0.3 28 29 3.57

2. 0.5 28.2 29.8 5.67

3. 0.8 30.3 33.7 11.22

4. 1.0 31 33.2 7.09

5. 1.5 31.7 31.1 -1.89

Fig 1. Percentage Compressive strength increase at 3rd ,7th & 28th day respectively.




Fig 2. Comparison of 28th day compressive strength of normal and admixed concrete

1.2Split tensile strength The split tensile strength results at the various ages such as 3, 7, 28 days and at admixture dosage of 0.3,

0.5, 0.8, 1.0, 1.5 % at a constant w/c ratio 0f 0.4 are presented in Tables below

Table 4 : 3rd day split tensile strength results


day split tensile Strength(Mpa) %age increase

(%) (3rd

day)

Normal Admixed

1. 0.3 0.98 1.05 7.14

2. 0.5 1.02 1.15 12.74

3. 0.8 1.11 1.21 9.01

4. 1.0 1.16 1.22 5.17

5. 1.5 1.23 1.19 - 3.25

Table 5: 7th day split tensile strength results



(%) (7th

day)

Normal Admixed

1. 0.3 1.72 1.81 5.23




2. 0.5 1.74 1.87 7.47

3. 0.8 1.82 1.95 7.14

4. 1.0 1.85 1.91 3.24

5. 1.5 1.88 1.85 - 1.59

Table 6: 28th day split tensile strength results



(%) (28th

day)

Normal Admixed

1. 0.3 2.81 2.85 1.42

2. 0.5 2.82 2.87 1.77

3. 0.8 2.84 2.91 2.46

4. 1.0 2.89 2.88 -0.34

5. 1.5 2.93 2.83 -3.41

Fig 3. Percentage split tensile strength increases at 3rd, 7th & 28th day




Figure 4:Comparison of percentage split tensile strength increase at 3rd, 7th and 28th day

1.3 Flexural strength The flexural strength results at the various ages such as 3, 7, 28 days and at Superplasticizer dosage of 0.3,

0.5, 0.8, 1.0, 1.5 % at a constant w/c ratio 0f 0.4 are presented in Tables below

Table 7: 3rd day flexural strength results


day flexural Strength(Mpa) %age increase

(%) (3rd

day)

Normal Admixed

1. 0.3 1.01 1.07 5.94

2. 0.5 1.08 1.21 12.03

3. 0.8 1.15 1.25 8.69

4. 1.0 1.19 1.24 4.20

5. 1.5 1.26 1.21 - 3.96

Table 8: 7th day flexural strength results


day flexural Strength(MPa) %age increase

(%) (7th

day)

Normal Admixed

1. 0.3 1.74 1.83 5.17

2. 0.5 1.78 1.91 7.30




3. 0.8 1.86 1.98 6.45

4. 1.0 1.89 1.93 2.11

5. 1.5 1.91 1.87 - 2.09

Table 9: 28th day flexural strength results


day flexural Strength %age increase

(%) (28th

day)

Normal Admixed

1. 0.3 2.86 2.88 0.69

2. 0.5 2.87 2.92 1.74

3. 0.8 2.88 2.96 2.77

4. 1.0 2.93 2.91 -0.68

5. 1.5 2.94 2.84 -3.52

Fig 5. Percentage flexural strength increase at 3rd , 7th & 28th day respectively.




Fig 6. Comparison of 28th day flexural strength of normal & admixed concrete

2.Compaction factor test results The compaction factor results at Superplasticizer dosage of 0.3, 0.5, 0.8, 1.0, 1.5 % at a constant w/c ratio

0f 0.4 are presented in table below

Table 10: Compaction factor results at different dosage of sodium lignosulphonate

S. No S.P. dosage Wt. Of Wt. Of mould and Wt. Of mould and C.F.

empty mould partially compacted fully compacted

Kg concrete Kg concrete Kg

1 0 14 25.10 27.00 0.853

2 0.3 14 25.75 27.20 0.890

3 0.5 14 26.05 27.30 0.906

4 0.8 14 26.30 27.35 0.921

5 1.0 14 26.10 27.10 0.923

6 1.5 14 25.95 26.90 0.926




Fig 7. Compaction factor at different admixture dosages

Different Admixture dosages to have constant workability

Choosing a constant workability of 0.92 C.F., the dosage of Superplasticiser at decreasing w/c ratios are

calculated and are presented in the table:

Table 11: admixture dosage at different w/c ratio to attain a constant workability

S. no W/c ratio S.P. dosage (%) C.F.

1 0.40 0.8 0.921

2 0.38 1.3 0.922

3 0.36 2.3 0.922

4 0.35 2.7 0.922

3 Strength tests at different w/c ratio of normal concrete The w/c ratio was gradually decreased and the strength tests were carried out at 3rd, 7th and 28th day age.

Table 12: Compressive strength results at different w/c ratio of normal concrete




S. No W/c ratio C.F. Compressive strength(Mpa)

3rd day 7th day 28th day

1 0.40 0.853 13.3 23.2 33.7

2 0.38 0.835 14 23.8 34.1

3 0.36 0.822 14.4 24.4 34.8

4 0.35 0.812 14.7 24.9 35.4

Fig 8. Compressive strength vs water cement ratio at constant workability

Table 13: flexural strength at constant workability

S. W/c S.P. C.F. flexural strength

No ratio dosage 3rd

day 7th

day 28th

day

1 0.40 0.8 0.921 1.28 1.94 2.98

2 0.38 1.3 0.922 1.30 1.96 3.0

3 0.36 2.3 0.922 1.27 1.93 2.96

4 0.35 2.7 0.922 1.23 1.91 2.92




Fig 9. Flexural strength vs water cement ratio at constant workability

Conclusion and recommendations

Conclusions The research presented in this thesis investigated the effect of retarding Superplasticiser sodium

lignosulphonate on properties of Portland cement concrete. Taking into account the findings of the study, the

following conclusions can be drawn:

1. Use of sodium lignosulphonate in concrete increases workability as seen in the compaction factor tests.

The increase in compaction factor is from 0.853 at 0 % to 0.926 at 1.5 % of admixture dosage.

2. It also causes the delayed setting of concrete due to its retarding effect as evident from increased initial

setting time and final setting time of cement paste. The initial setting time increases from 1h 20m for normal

to 2h 52m for 1.5% admixed concrete. Similarly the increase in final setting time is from 3h 06m to 5h 23m.

3. The compressive strength, split tensile strength and flexural strength of concrete increases with the dosage

till the maximum at the optimum dosage and then starts decreasing and is even less than the normal concrete

after certain limit of dosage.

4. The maximum increase in compressive strength of the admixed concrete at constant w/c

ratio of 0.4 is 11.86 % for 3rd

day, 15.84 % for 7th

day and 11.22 % for 28th

day testing than the normal

concrete at 0.8 % (optimum dosage) of the admixture dosage which decreases to - 1.89 % at 1.5 % of

admixture dosage. Thus increasing the admixture dosage unnecessarily beyond the optimum dosage does not




increase the strength accordingly.

5. The maximum increase in split tensile strength of the admixed concrete at constant w/c

ratio of 0.4 is 9.01 % for 3rd

day, 7.47 % for 7th


day testing than the normal concrete

at 0.8 % (optimum dosage) of the admixture dosage which decreases to -3.41 % at 1.5 % of admixture dosage.

6. The maximum increase in flexural strength of the admixed concrete at constant w/c ratio

of 0.4 is 12.03 % for 3rd

day, 7.30 % for 7th


day testing than the normal concrete at

0.8 % (optimum dosage) of the admixture dosage which decreases to -3.52 % at 1.5 % of admixture dosage.

7. With the decrease in w/c ratio there is an increase in the admixture dosage to achieve a constant workability.

E.g. for w/c ratio of 0.4 and 0.35, the dosage required is 0.8 % and 2.7 % respectively for a constant

workability of 0.92.

Recommendations For the study done over the effect of retarding Superplasticiser sodium lignosulphonate on the properties of

Portland cement concrete, the following recommendations are proposed,

1. Since the compressive strength of admixed concrete showed increasing trend only up to0.8 % for

28th

day strength, the use of the admixture should be limited to 0.8%.

2. In high rise building constructions where high strength concrete is needed, lignosulphonate may be made use of

3. In mass concreting these admixtures may be made use of, for controlling the high rate of heat of hydration

4. In ready mixed concrete, for keeping the concrete fresh for a sufficiently large time the admixtures may be easily used

5. Because of the large increase in workability, these admixtures may be used in highly reinforced sections such as beams and columns.

6. Because of the decrease in permeability of concrete, which is useful in water retaining structures,

these should be used in hydraulic structures.


effects on properties of m25 grade concrete mix using ... · jetir1805634 journal of emerging...

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