Desirable Chemical Composition of Brick Earth

The desirable chemical composition of brick earth for good quality bricks are given below (IS: 1077, 1976):

1. Alumina or clay – 20 to 30% by weight
2. Silica or sand – 35 to 50% by weight
3. Silt – 20 to 25% by weight
4. Other required ingredients are
   1. Iron oxide
   2. Magnesia
   3. Lime
   4. Sodium potash, etc.
5. In the case of alluvial soils, the total lime and magnesia should not be more than 1%; in other soils it should be less than 15%.
6. Water-soluble materials in total should be less than 1%.