Constituents of good brick earth:

Bricks are the most commonly used construction material. Bricks are prepared by moulding clay in rectangular blocks of uniform size and then drying and burning these blocks. In order to get a good quality brick, the brick earth should contain the following constituents.

Silica

Alumina

Lime

Iron oxide

Magnesia

Silica

Brick earth should contain about 50 to % of silica.

It is responsible for preventing cracking, shrinking and warping of raw bricks.

oIt also affects the durability of bricks.

oIf present in excess, then it destroys the cohesion between particles and the brick becomes brittle.

Alumina

Good brick earth should contain about 20% to 30% of alumina.

It is responsible for plasticity characteristic of earth, which is important in moulding operation.

If present in excess, then the raw brick shrink and warp during drying.

Lime

The percentage of lime should be in the range of 5% to 10% in a good brick earth.

oIt prevents shrinkage of bricks on drying.

oIt causes silica in clay to melt on burning and thus helps to bind it.

Excess of lime causes the brick to melt and brick looses its shape.

Iron oxide

A good brick earth should contain about 5% to 7% of iron oxide.

oIt gives red colour to the bricks.

oIt improves impermeability and durability.

oIt gives strength and hardness.

oIf present in excess, then the colour of brick becomes dark blue or blakish.

o If the quantity of iron oxide is comparatively less, the brick becomes yellowish in colour.