Brick is smallest structural unit of any structure. The brick may be of different types but it constituents same material, only percentage of material varies. The major constituent of bricks are:
1. Silica:
The good brick earth contain 50% to 60% of silica. Silica exist in clay either as combined form with alumina or as free. It prevent cracking, shrinkage and warping of raw material. It also provide uniform shape to bricks. Excessive amount of silica make brick brittle by destroying cohesion b/w particles.
2.Alumina:
Good brick contains 20% to 30% of alumina. It is main constituent of clay. It impart plasticity property to brick and help in moulding process. Excessive amount of it make raw bricks shrink and warp during drying and hard when burnt.
3. Lime:
The quantity of lime should not exceeded from 5% in very fine powdered form. It prevent shrinkage of raw materials. On heating at kiln temperature, sand slightly fuse in presence of lime. It work as cementing material. The excess amount of it cause brick melt which destroy shape of brick. If lime is present in form of lumps, coverted into quick lime after burning and then quick lime expand in form of moisture which break brick into pieces.
4. Iron oxides:
The amount of iron oxide should varies b/w 5 to 6 percent is good for brick. It impart red colour to brick and help lime to fus sand. Dark blue or Blackish colour of brick represent presence of excessive amount of iron oxides. If colour is yellowish, then it represent presence of lesser amount of iron oxides.
5.Magnesia:
A very small amount of it impart yellowish colour to brick and also reduce shrinkage of brick. Excessive amount of it cause decay of bricks.
0 Comments