Bricks, composition and its function

Bricks wall

Bricks, composition and its function

 Brick may be defined as the block of rectangular shape and suitable size that are made from suitable type of clay by different process involving moulding, drying and burning.
 According to Wikipedia, a brick is building material used to make walls, pavements and other elements in masonry construction. 
The depression on the top of brick is known as frog. The size of the frog is approximately 10 cm in length, 4 cm in width and 1 - 2 cm depth.
The common brick is one of the oldest building material and it is extensively used at present as a leading material of the construction because of its durability, strength, reliability, low cost and easy availability.
The Great Wall of China (210 B.C.) was built with both burnt and un burnt (sun dried bricks).
In India the standard size of traditional brick is recommended by Bureau of Indian Standard  (BIS) is 9" × 4.5" × 3". The nominal size of brick as recommended by BIS is 19 cm × 9 cm × 9 cm without mortar. The size of brick tile is 20 cm × 10 cm × 10 cm with mortar. The size of the brick tiles is 19 cm × 9 cm × 4 cm without frog. The average weight of brick is 3.2 kg to 3.5 kg.

 Composition of good brick earth 

A good brick earth should be such that when prepared with water it can be easily moulded, dried and burnt without cracking or warping. The composition of good brick earth are clay ( alumina ) 20 - 30 % by weight, sand  ( silica ) 50 - 60 %  by weight, iron oxide 4 - 6 % by weight, lime 4 - 6% by weight, magnesia 1 - 2 % by weight.

 Function of the constituents of good brick earth

Sand or Silica in brick earth prevents shrinkage, cracking and warping of bricks. But too much of sand will makes the brick brittle.
Clay or Alumina makes brick earth plastic and is capable of being moulded to any shape. If Clay or Alumina is present in excess, raw bricks shrink and warp during drying and burning.
A small amount of Lime is desirable in good brick earth. Excess of Lime causes the brick to melt and hence its shape may be lost.
A small amount of Iron-oxide helps lime to fuse sand and impart red colour to bricks. Excess of Iron oxide makes the bricks dark blue or blackish. If it is present in less quantity brick will be yellowish in colour.
A small quantity of Magnesia in brick earth imparts yellow tint to bricks and decreases shrinkage. But excess of Magnesia leads to decay of bricks.