Bricks MCQ with answer and solution

Concept

Silica stops shrinkage and warping, but too much silica destroys cohesion and makes the brick brittle and weak when burnt.

Step-by-step solution

1. Good brick earth has about 50-60% silica and 20-30% alumina. 2. Silica gives shape and prevents shrinkage, cracking and warping. 3. Excess silica destroys the binding between particles. 4. So on burning the brick becomes brittle and weak. 5. Answer is (A).

Explanation

Silica keeps the brick in shape and stops shrinkage. If silica is too much, the particles do not bind well. The burnt brick then becomes brittle and weak.

Why the other options are wrong

(B) Cracking on drying is caused by excess alumina, not silica. (C) Melting on burning is caused by excess lime or alkalis. (D) Warping is caused by excess alumina. Silica actually prevents warping.

Shortcut

Silica excess = brittle. Alumina excess = crack and warp. Lime excess = melt.

Common mistake

Choosing warp, but silica prevents warping. Excess alumina causes it.