Brick is the material that is formed by the composition of silica, alumina, iron oxide, etc. Using these materials in an appropriate ratio makes the brick strong and sound but improper ratio of materials leads to weakness. For strong, sound and durable brick, it should be free from different harmful ingredients like excess lime, organic matters, stones & pebbles, etc. Some harmful ingredients in brick earth are briefly explained below.
Harmful ingredients in brick earth
a. Amount of limestone present in the brick should not be more than 1%.
b. Excessive limestone leads to the changing of colour of brick from red to yellow.
c. Lime should not be present in lumps because it absorbs moisture, swells and causes disintegration of the brick.
d. Excess lime also leads to melting of brick which affects the shape.
2) Organic Matter:
1. It makes the brick dark and porous in nature.
b. Almost all the organic matters present in brick are burnt down during the burning process of brick. If completely not burn then it will lead to problems like porous, darkness, etc.
c. The use of more than 1% of organic matter in brick leads to problems.
d. Excessive organic matter results in the formation of tiny pores which increases the water absorption capacity of brick that leads to weakness of brick.
3) Sulphides and Sulphates:
a. Sulphide and sulphate affect the bricks. The improper shape of bricks may be due to the presence of sulphates and sulphides.
b. It causes crystallization and disintegration during the burning of brick, so it may split the brick into pieces.
a. Alkali creates additional softening of brick which causes twisting and warping.
b. It causes melting which leads to the improper shape of a brick.
5) Pebbles of stone and gravel:
a. The presence of pebbles in brick leads to non-uniform mixing of clay which may lead to non-uniform shape and also make brick porous.
b. Brick containing pebbles may break down into pieces when a very small amount of load is subjected.
6) Iron Pyrites
a. Pyrites discolourise the brick.
b. It also leads to disintegration and crystallization during the burning of brick because of oxidation of the iron pyrites. This causes improper shape, splitting, etc.
a. Using water containing a small amount of magnesium or calcium carbonates, together with a sulphurous fuel leads to an improper size, crystallization and sometimes disintegration.
b. Combined water generally causes shrinkage.
8) Carbonaceous Materials
a. They generally lead to the black colour of the brick.