admixtures

Question 1

What is a chemical admixture?

Answer 1

Admixtures are substances introduced into concrete, during or immediately before its mixing, to alter or improve the properties of the fresh or hardened concrete, or both.

Question 2

Main Types of admixtures?

Answer 2

1. Accelerating
2. Retarding
3. Air-Entraining
4. Water-Reducing

Question 3

How accelerating admixtures effect concrete?

Answer 3

Handling time is reduced.
Increased heat evolution due to rapid hydration.
Increase early strength, particularly at 1 day.
Increase drying shrinkage and creep.

Question 4

How do retarding admixtures effect concrete?

Answer 4

Increase the rate of loss of workability, hence decrease in handling time, even though the setting time has increased.
Reduce heat evolution at early stages.
Increase in ultimate strength.
Increase in the rate of drying shrinkage and creep, but not ultimate value.

Question 5

Air entraining admixtures

Answer 5

Ask Gus, too much to write

Question 6

WATER REDUCING ADMIXTURES

Answer 6

look at the table in slides gus is lazy

Question 7

Other types of admixtures.

Answer 7

Pore fillers, corrosion inhibitors, anti bacterial admixtures, bonding admixtures, water repellers, pigmenting admixtues.