Manufacturing Of Bricks
Green bricks contain about 7 - 30% moisture depending upon the method of manufacture. Theobject of drying is to remove the moistre to controlthe shrinkage and save fuel and time during burning.The drying shrinkage is dependent upon pore spaceswithin the clay and the mixing water. The additionof sand or ground burnt clay reduces shrinkage,increases porosity and facilities drying. The moisturecontent is brought down to about 3 per cent underexposed conditions within three to four days. Thus,the strength of the green bricks is increased and the bricks can be handled safely. Clay products can be dried in open air driers or in artificial driers. The artificial driers are of two types, the hot floor drier and the tunnel drier. In the former, heat is applied by a furnance placed at one end of the drier or by exhaust steam from the engine used to furnish power and is used for fire bricks, clay pipes and terracotta. Tunnel driers are heated by fuels underneath, by steam pipes, or by hot air from cooling kilns. They are more economical than floor driers. In artificial driers, temperature rarely exceeds 120 o C. The time varies from one to three days. In developing countries, bricks are normally dried in natural open air driers (Fig. 11). They are stacked on raised ground and are protected from bad weather and direct sunlight. A gap of about 1.0 m is left in the adjacent layers of the stacks so as to allow free movement for the workers.