Harmful Ingredients in Clay Bricks.

Harmful Ingredients in Clay Bricks.

1- lime: Excess of lime makes the colure of the brick yellow instead of red. Limps of limestone remaining in the finished brick are undesirable because, when such a brick comes in contact with water, lime will begin to slake. During slaking, lime expands and also generates heat. Due to this, stresses will be produced, which will result in producing cracks in bricks. A certain quantity of lime is desirable as it binds the particles of brick together and reduces shrinkage on drying.
2. Iron pyrites: tend to oxidize and decompose the brick during burning. The brick may split into pieces. Pyrites discolourise the bricks.
3. Pebbles: The presence of pebbles, girt, gravel etc. will be undesirable because they prevent the clay from being mixed well. They spoil the manufacture of smooth and regular, standard bricks. Pebbles, gravel, grit, etc., should be removed before mixing.
4. Organic matter: This includes leaves, twigs of plants, roots, grass, bones of animals etc. On burning green bricks, the organic matter gets charred and leaves porous making the bricks porous (this is due to the fact that the gasses will be evolved during the burning of the carbonaceous matter and it will result in the formation of small porous).
5. Alkalis (MgO , K2O):If alkalis are present in the clay brick, they lower the fusion point of clays and cause the brick to fuse, twist and warp during burning. Alkalis salts if Present in finished bricks absorb moisture from the atmosphere and create damp condition which are detrimental to health. Further when the moisture dries up a grayish white deposit is left