In this article, we can take a look on What are the constituents of good brick earth? and What constituents render bricks earth unsuitable for manufacturing bricks?
Constituents of Good Brick Earth
First, we discuss Constituents of good brick earth which play a great role in manufacturing brick
It is the principal component of the bricks earth and good brick earth must contain about 20-30% alumina.
Alumina gives plasticity to the earth thereby making the moulding of bricks earth easier.
However excess alumina leads to shrinkage and warping of bricks.
Identify the percentage of silica in good brick earth – 50 to 60% silica in good brick earth is desirable.
Silica exists in clay either free or in combined form. It prevents shrinkage, warping and cracking of bricks apart from imparting a uniform shape to the bricks.
However excess silica destroys the cohesion between the particles of the bricks earth and the bricks become brittle.
About 5 to 6% iron oxide is desirable in good brick earth.
Iron oxide gives a red colour to bricks.
Excess of iron oxide leads to dark colouration in bricks like dark blue or blackish colour.
However less quantity of iron oxide makes the bricks yellowish in colour.
About less than 5% of lime should be present in good brick earth. It should be in the very finely divided powder form.
It prevents shrinkage of bricks.
Excess of lime causes bricks to melt thereby losing their shape.
A very small quantity of magnesia gives the yellow colour to bricks.
It also decreases shrinkage.
Unsustainable Brick Constituent
Now, we learn something about Constituents that make the bricks of earth unsustainable
Pebbles in brick earth does not allow uniform mixing of clay thereby leading to weak and porous bricks.
Iron pyrites cause the bricks to disintegrate on burning because of the oxidation of iron.
Alkalies (particularly soda and potash) acts as a flux in the kiln and they cause bricks to fuse.
Also, alkalies absorb water from the bricks masonry.
This moisture on evaporations leaves behind a white patch on the surface of bricks masonry.
Presence of vegetation and other organic matter in brick earth aids in burning.
However such matters if remains partially burnt then bricks will become porous due to the evolution of gases on burning.
Excess lime makes the bricks lose their shape.
FAQ 1: Which are Unsustainable Brick Constituent?
Pebbles, Iron Pyrites, Alkalies, Vegetation, Excess Lime
FAQ 2: Proportion of alumina in brick earth?
20% to 30%