BRICKS 

DEFINITION: The brick may be defined as a uniformly burnt rectangular unit having high compressive strength .

BRICKS EARTH AND ITS CONSTITUENTS 

The earth used for manufacturing of bricks should have desired constituents so that a good type of brick can be made

1.ALUMINA
2.SILICA
3.LIME
4.OXIDE OF IRON
5.MAGNESIA

ALUMINA:    Alumina is responsible for imparting the plastic character to the clay in wet condition. it is main constituent of every kind of clay. if brick contain excess of alumina, then the brick will shrink more on drying and less alumina alumina leads to many difficulties in moulding of bricks so a good brick earth should have alumina content between 20% to 30%.

SILICA :   silica may be present in free form or in combined form in the clay. It prevents shrinkage, cracking and warping of bricks but too much of sand will make bricks brittle. the durability of bricks depend upon the proper proportion of silica in bricks earth. the silica content should be about 50% to 60% in good bricks earth.

LIME:       Lime should be present in very finely powdered form which is thoroughly dispersed in bricks earth. A lime content of 5% is desirable in a good bricks earth . Lime is responsible for strenght and durability of bricks lime present in small proportion also prevents shrinkage of raw bricks.

OXIDE OF IRON :  A small quantity of iron oxide is helpful to use silica at comparatively low temperature and imparts the red colour to the burnt bricks. The content of oxide iron should be 5% to 6%. Iron oxide increase  the durability and impermeability of the bricks.

MAGNESIA :   Magnesia presents in clay with oxide of iron make the bricks yellow . It is present in very small proportion and decreases the shrinkage. But excess of magnesia causes decay of bricks.

                                         

NOTE : In addition to above matter present in good brick earth , some ingredients are harmful for it. They give adverse effects on the properties of bricks

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