CIVIL

1. INTRODUCTION
• Admixtures are ingredients other than basic ingredients cement,
water and aggregates that are added to concrete batch immediately
before or during mixing to modify one or more of the specific
properties of concrete in fresh and hardened state.
• Added in small quantity either in powder or liquid form
• Combination is used when more than one property to be altered.

2. PURPOSE
1. To modify fresh property
• Increase the workability without increasing the water cement
ratio or decrease the water content at the same workability.
• Retard or accelerate the time of initial setting.
• Reduce or prevent the settlement or create slight expansion.
• Modify the rate or capacity of bleeding.
2. To modify harden property
• Reduce the heat of evolution.
• Accelerate the rate of strength development at early stages.
• Increase the durability
• Decrease the permeability of concrete.

3. Classification of admixtures
1. Accelerating admixtures
2. Water reducing admixtures
3. Retarding admixtures
4. Air entraining admixtures
5. Mineral
6. Super plasticizers

4. Super plasticizers
• These are the modern type of water reducing admixtures, basically a
chemical or a mixture of chemicals that impart higher workability to
concrete.
• Three different purposes or a combination of these
 to increase workability without changing the mix proportion.
 to reduce the mix water and W/C ratio in order to increase the
strength and improve the durability.
 to reduce both water and cement in order to reduce creep
shrinkage and thermal strains caused by heat of cement
hydration.

5. • Super plasticizers (SP) are basically classified in the following
categories:
1. sulphonated melamine formaldehyde condensate (SMF)
2. sulphonated naphthalene formaldehyde condensate (SNF)
3. modified ligno-sulphonates (MLF)
4. other organic compounds ( sulphuric acid ester and
carbohydrate ester)
• There are three possible ways in which super plasticized concrete can
be produced :
1. High workability concrete,
2. Concrete with low water/ cement ratio,
3. Concrete with reduced cement content.

6. Material
• Cement: Ordinary Portland Type-1 cement was used.
• Fine Aggregates: Fine aggregates confirming to the gradation of
ASTM-136 were used.
• Coarse Aggregates: Lime stone crushed stones of size1/2 in and
below were used.

7. Review
• Two types of super plasticizers (Rheobuild 1100, Rheobuild 561M)
• Three nominal ratios of 1:1:2, 1:1.5:3 and 1:2:4
• The water cement ratio as 0.50, 0.55 and 0.60
• Experiments have been divided into three series namely
a) Series No 1: workability series,
b) Series No 2: water reduction series,
c) Series No 3: cement saving series

8. Series No 1 (workability series)
A. EFFECT ON WORKABILITY AND COMPRESSIVE STRENGTH
• Slump tests were carried out
• Cubes [6*6*6] were tested at the ages of 3,7,28 days.
a. Mix proportion 1:2:4
Test results showing effect of super plasticizers on compressive strength
and workability at constant w/c ratio.

9. Effect of SP on Compressive strength at constant W/C ratio
• Rheobuild 561M gives better results than Rheobuild 1100.

10. b: Mix proportion 1:1.5:3
Test results showing effect of super plasticizers on compressive strength
and workability at constant w/c ratio

11. Effect of SP on Compressive strength at constant W/C ratio
• 7 day compressive strength increase was commendable when
compared to mix proportion of 1:2:4.

12. c: Mix proportion 1:1:2
Test results showing effect of super plasticizers on compressive strength
and workability at constant w/c ratio

13. Effect of SP on Compressive strength at constant W/C ratio
• The increase in 3 day compressive strength was great as compared to
other two mix proportions.

14. B. EFFECT ON SPLITTING TENSILE STRENGTH
• Cylinders (6*12”) was tested by splitting tests at the age of 28days
a: Mix proportion 1:2:4
Test results showing effect of super plasticizers on splitting tensile
strength of concrete at constant w/c ratio

15. b: Mix proportion 1:1.5:3
Test results showing effect of super plasticizers on splitting tensile
strength of concrete at constant w/c ratio

16. c: Mix proportion 1:1:2
Test results showing effect of super plasticizers on splitting tensile
strength of concrete at constant w/c ratio
• Increases in splitting tensile strength at a constant W/C ratio.
• Slump values for the same w/c ratio are slightly different from the
case of compressive strength and workability.

17. C. EFFECT ON (MODULUS OF RUPTURE) FLEXURAL
STRENGTH
• Standard plain concrete beams were tested at third point load after
28days of pouring.
a: Mix proportion 1:2:4
Test results showing effect of super plasticizers on modulus of rupture
(flexural strength) of concrete at constant w/c ratio (series-1) Mix
proportion 1:2:4

18. b: Mix proportion 1:1.5:3
Test results showing effect of super plasticizers on modulus of rupture
(flexural strength) of concrete at constant w/c ratio (series-1) Mix
proportion 1:1.5:3

19. c: Mix proportion 1:1:2
Test results showing effect of super plasticizers on modulus of rupture
(flexural strength) of concrete at constant w/c ratio (series-1) Mix
proportion 1:1.5:3

20. Series No 2
• The water content was gradually increased, at constant workability.
• Keeping all other ingredients of the mix constant, increasing the
dosages of the SP to compensate for the loss in workability.
• SURAJ
Test results showing effect of super plasticizer on water reduction and
compressive strength at constant workability (series-2) mix ratio
(1:1.5:3)

21. Effects of super plasticizer on compressive strength at constant
workability

22. Test results showing effect of super plasticizers on water reduction and
compressive strength at constant workability (series-2) mix ratio
(1:1.5:3)

23. Effects of super plasticizer on compressive strength at constant
workability

24. Series No 3
• Cement content and water content were reduced keeping
water/cement ratio and workability as constant
• SURAJ
• SURAJ
Test results showing effect of super plasticizer on cement saving at
constant work ability and constant w/c ratio (series 3) mix ratio (1:1.5:3

25. Test results showing effect of super plasticizer on cement saving at
constant work ability and constant w/c ratio (series 3) mix ratio (1:1.5:3)