Admixture and types of admixture

Admixture 

Admixture are the material used in the man manufacturing of concrete which control the water cement ratio and increase or decrease the hydration rate & work for strength , they are present in powder & fluid form

Types of admixture

1). Accelerator

They increase the rate of hydration and speed up the chemical reaction by which setting time comes earlier 

eg. CaCl2 ( most famous)

Less famous → Na2SO4,NaOH, Na2CO3 etc.

2). retarder

They slow down the rate of hydration by which setting time comes later.

eg. Gypsum (CaSO4.2H2O)

Less famous → sugar cellulose, alcohol, oil etc

3). Air entrained

→ an air entraining agent add in concrete in the form of air bubbles which increase the workability of concrete but reduce the strength.

➔ it control the bleeding and segregation 

eg. sop bubbles, vinsol resin

4). plasticizer (water Reducer)

To control the water cement ratio & improve the plastic nature & workability, they are added in concrete 

eg. hydroxylated carboxylic acid with sodium solution. dose → 200 ml-450ml per 100 kg cement