Question

Consider the following statements:
Pozzolana used as an admixture in concrete has the following advantages:
1. It improves workability with lesser amount of water
2. It increases heat of hydration and so sets the concrete quickly.
3. It increases resistance to attack by salts and sulphates.
4. It leaches calcium hydroxide.
Select the correct answer using the codes given below:

• A. 1, 2, 3 and 4
• B. 1, 2 and 4
• C. 1 and 3
• D. 2, 3 and 4

Answer 1

The correct option is C 1 and 3

A mineral additive also called a supplementary cementitious material (pozzolana) is finely ground siliceous material which does not possess cementitious property in itself, but react with calcium hydroxide (released from hydration of portland cement) to form compounds of low solubility having cementitious property. This is called pozzolanic action.
It reduces permeability, improve workability and increase resistance to chemical attack. The leaching of calcium hydroxide is avoided as $Ca(OH{)}_2$ is converted to cementitious product by pozzolanic action.