What is the purpose of adding gypsum to cement during its production?
- ATo increase strength
- BTo control setting timeCorrect
- CTo improve colour
- DTo reduce heat
Solution
Concept
Gypsum in cement
Step-by-step solution
1. Gypsum (about 3–5%) reacts with C₃A. 2. This prevents flash set and controls the setting time.
Explanation
Without gypsum cement would set almost immediately because of the fast hydration of C₃A.
Why the other options are wrong
Gypsum does not improve strength, colour or heat of hydration.
Shortcut
Gypsum = set controller.
Common mistake
Choosing strength.
Correct answer: B) To control setting time