FLYASH LIME BRICKS SPECIFICATION

Fly ash is a useful by‐product from thermal power stations using pulverized coal as a fuel and has considerable pozzolanic activity. This national resource can be gainfully utilized for manufacture of fly ash‐lime bricks as a supplement to common burnt clay building bricks leading to conservation of natural resources and improvement in environmental quality. Fly ash‐lime bricks are obtained from materials consisting of fly ash in major quantity, lime and an accelerator acting as a catalyst.

Fly ash‐lime bricks are generally manufactured by inter‐grinding or blending various raw materials which are then molded into bricks and subjected to curing cycles at different temperatures and pressures. On occasions, as and when required, crushed bottom ash or sand is also used in the composition of the raw material. Crushed bottom ash or sand is used in the composition as a coarser material to control water absorption in the final product. Fly ash reacts with lime in presence of moisture to form a calcium silicate hydrate which is the binder material. Thus fly ash‐lime brick is a chemically bonded brick. These bricks are suitable for use in masonry construction just like common burnt clay bricks. Production of fly ash‐lime building bricks has already started in the country and it is expected that this standard would encourage its production and use on mass scale. This standard lays down the essential requirements of fly ash‐lime bricks so as to achieve uniformity in the manufacture of such bricks.