Clay bricks shall be hand or machine moulded, allowance being made for shrinkage in drying and burning. Clay bricks shall be free from cracks and flaws and nodules of free lime. Bricks of 9 cm height shall be moulded with a frog 1 cm or 2 cm deep on one of its flat sides. these bricks are used in general, for different types of building works.
Classification of Clay Bricks:
Class I Bricks - They shall have uniform color, shall be thoroughly burnt but not over-burnt, shall have plain rectangular faces with parallel sides and sharp straight edges. They shall have fine, compact and uniform texture, and emit a clear ringing sound when struck against each other.
Class II Bricks - They shall have uniform color and may be slightly over-burnt. The bricks may be slightly distorted and have round edges. They shall have fine, compact, uniform texture and emit a clear ringing sound when struck.
Class III Bricks - They may be slightly under-burnt or over-burnt. They may be distorted and have round edges. The defects in uniformity and shape shall not be such to cause difficulty in obtaining uniform courses with their use.