Bricks MCQ with answer and solution

Concept

Freeze-thaw durability of masonry bricks

Formula

Water Absorption % = ((W2 - W1) / W1) × 100 ≤ 15%

Step-by-step solution

1. Freeze-thaw deterioration occurs when absorbed water expands by approximately 9% upon freezing within brick pores. 2. Bricks with high porosity or high water absorption absorb large moisture volumes, generating internal hydraulic pressures that cause spalling. 3. High-density burnt clay bricks with low water absorption (<15%) possess a dense vitrified matrix that minimizes water intake. 4. Hence, high-density burnt clay bricks with low water absorption are most suitable for freeze-thaw regions. Answer: B

Explanation

In freeze-thaw environments, water entering open pores expands upon freezing, generating expansive hydraulic pressure that causes spalling and disintegration. High-density burnt clay bricks with low water absorption and dense pore structures restrict moisture ingress, preventing frost degradation. First-class well-burnt bricks are therefore mandatory for exposed masonry in freezing regions.

Why the other options are wrong

A) Low-density hollow bricks allow water accumulation within cavities, accelerating frost shattering. C) Sun-dried unburnt bricks disintegrate upon wetting and have zero frost resistance. D) Perforated bricks with high porosity trap excessive water and rapidly spall in freezing weather.

Shortcut

Freeze-thaw resistance = Dense body + Low water absorption + Low porosity.

Common mistake

Selecting hollow or porous bricks under the misconception that air spaces relieve freeze-thaw stresses.