Bricks for building construction

Bricks are the one of the oldest building materials and still it has been used in many part of the world. Bricks are quite economical, easy to use and handle and durable. In general, bricks are made in rectangular shape which can be carried by one hand. The various ingredients of a good brick are silica (50%), Alumina (20%), Lime (10%), Alkalis (10%), ferric oxide (7%), magnesia (less than 1%), carbon dioxide (small traces), sulphur trioxide (small traces) and water (small traces). Optimum amount of Silica ensures durability. It also helps to retain its shape and prevents shrinkage and warping. Excess amount of Silica produces brittleness. Alumina is used to absorb water and rendering the clay plastic. If alumina is added beyond the limit, it will result in cracks. Addition of lime reduces the shrinkage on drying. Lime also increases binding power of silica and lowers the fusion point. Alkalis are acting as flux. Ferric oxide gives red colour to brick, enhances durability, improves impermeability, lowers the fusion point and adds strength and hardness. Magnesia imparts yellow colour to brick. While selecting bricks for building construction, various characteristics to be considered are size, shape, texture, water absorption, compactness, soundness, hardness, crushing strength and brick earth.