Bricks are made out of clay, clay is moulded to desired shape and size to make sun dried or burnt brick . The clay of brick contain iron oxide, lime iron pyrites pebbles of stone and gravel alkalies etc.
Iron oxide gives red colour to the brick. Lime binds the particles while burning and reduces shrinkage although excessive lime melts the brick.
The sequence of making brick are – Digging – weathering – blending – tempering – moulding – drying – and burning .
Pug mill is used for tempering the brick earth, then hand moulding or machine moulding is done. Bricks are dried in sun or in controlled room environment then they are burnt in kilns or clamps
Kiln burnt brick are of superior quality. Widely used kiln are Bull trench and Hoffman’s kiln.
Well burnt with uniform red colour crack free brick are good quality brick, they produce clear ringing sound when they are struck against each other . Water absorption should be limited to 15 by weight when kept in water for about 24 hours. Crushing strength should be more than 55 kg/cm2
Brick may be of different types, bricks which withstand high temperature are refractory bricks alumina content is more in these bricks.
They are different sizes of bricks in India, Is bricks is 19cmx9cmx9cm and with mortar it becomes 20cmx10cmx10cm. Different pwd uses different sizes of bricks.
Perforated bricks hollow bricks and coping bricks king closer bricks Queen closer bricks are some types of bricks.
Test on Bricks –
For testing the suitability brick may be tested for –