Question

Portland cement contains ‘X’ to enhance the setting time. What is ‘X’?

• A. $CaSO_4.\frac 12 H_2O$
• B. $CaSO_4.2H_2O$
• C. $CaSO_4$
• D. $CaCO_3$

Answer 1

Answer: (B)

$CaSO_4.2H_2O$

Answer 2

When mixed with water, the setting of cement takes place to give a hard mass.
This is due to the hydration of the molecule of the constituents and their rearrangement. The purpose of adding gypsum $(CaSO_4.2H_2O)$ is only to slow down the process of setting of the cement so that it gets sufficiently hardened.

So, the correct option is (B): $CaSO_4.2H_2O$