ANS:C - warping of bricks

Good quality bricks contain 50-60% silica. Silica prevents raw bricks from cracking, shrinking and warping. The higher the proportion of sand, the more and shapely and uniform in texture will be the brick. Although, excess silica destroys cohesion between the brick clay particles and makes brick brittle and weak. The amount of silica (sand) present in brick earth is 50-60% and it prevents cracking and warping of raw bricks