Building Materials MCQ Questions & Answers | Civil Engineering

Cement setting is a chemical reaction that causes it to harden. To control this process and prevent it from setting too quickly, we add certain compounds.

Gypsum (calcium sulfate) is specifically added to cement to retard, or slow down, the initial setting time. This ensures that the cement has enough time to be mixed and placed before it hardens. The other options listed (tri-calcium silicate, di-calcium silicate, and tri-calcium aluminate) are all components of cement itself, but they do not primarily control the initial setting time in the same way gypsum does.

Therefore, the correct answer is B: Gypsum.

The correct answer is Option B: Cellulose paints
Here's why:

* Duco paints are a type of lacquer.
* Lacquers are known for their fast-drying, durable, and glossy finish.
* Cellulose paints are a common type of lacquer.
* They use cellulose nitrate or cellulose acetate as the main film-forming ingredient.

Let's look at the other options:

* Plastic paints: While they might contain plastics, this is too broad a term. Duco is a specific type of paint, not just any paint with plastic in it.
* Emulsion paints: These are water-based paints, and Duco paints are generally solvent-based.
* Oil paints: Oil paints dry slowly and have a different composition than Duco paints.