The GATE Grind

GATE 2022 CE (CE1) – Question 15

Construction Materials · Cement: hydration, admixtures · 1 mark · Multiple choice

Which of the following equations is correct for the Pozzolanic reaction?

  1. Ca(OH)2 + Reactive Superplasticiser + H2O → C-S-H
  2. Ca(OH)2 + Reactive Silicon dioxide + H2O → C-S-H
  3. Ca(OH)2 + Reactive Sulphates + H2O → C-S-H
  4. Ca(OH)2 + Reactive Sulphur + H2O → C-S-H

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) Ca(OH)2 + Reactive Silicon dioxide + H2O → C-S-H

Explanation

A pozzolan supplies reactive silica, which reacts with calcium hydroxide released during cement hydration in the presence of water. The product is additional calcium silicate hydrate, C–S–H.

Therefore **Ca(OH)₂ + reactive silicon dioxide + water → C–S–H**, **B**. Superplasticizer and reactive sulfur species are not the silica reactant.