Harmful Ingredients In Brick Earth/ composition of bricks

Composition of Brick Earth : Function of Brick Ingredients


Brick is one of the key materials used in the construction of structures. Good composition of materials leads to the durability and high strength of the brick.

Brick is the composition of Silica, Alumina, Iron Oxide, Magnesia, Organic matter, etc.

The composition of bricks should be:



Percentage in brick

Silica (SiO2)55%
Alumina (Al2O3)30%
Iron Oxide (Fe2O3)8%
Magnesia (MgO)5%
Organic Matter1%



  Composition of Brick Earth  


 i. Alumina

* It is the main principle constituent of every kind of brick. It acts as a cementing material in raw brick.

* It gives plasticity to the earth and makes the brick hard.

* Good brick contains about 30% of alumina.

* Excess amount of alumina may result in the shrink, warp, or crack in the brick on burning or drying.


ii. Silica

* Silica imparts hardness to the brick.

* Addition of silica also increases durability and resistance to heat.

* Good brick contains about 55% of silica.

* Excessive silica may lead to brittle or weak brick.


iii. Lime

* When lime is present in small quantities in freely divided states, it reduces shrinkage of bricks, helps silica melt at a lower temperature, and binds the particles of the brick together resulting in greater strength of brick.

* Excess lime causes the brick to melt and lose shape.

* Good brick contains about 1% of lime.


iv. Iron Oxide

* Iron Oxide imparts a red color to the bricks.

* Good brick contains about 8% of Iron oxide.

* It helps silica to fuse at a low temperature.


v. Magnesia

* A small proportion of magnesium decreases shrinkage and gives a yellow tint to the bricks.

* An excess amount of magnesia causes bricks to decay.

* Good brick contains about 5% of magnesia.



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