Sand lime bricks: These are very strong & hard bricks. Sand for these should be coarse (but not very coarse), clean, free from salts or organic matter, with grains of assorted sizes, & well graded so as to have min voids. Lime to be well burnt, free from ashes. It should be a high calcium lime, containing 90-90% of Cal. oxide & not more than 0.5% of magnesium oxide & filled in moulds. The moulded bricks are then placed for hardening in a closed cylinder called Autoclave for 10 hrs. Generally, the bricks are moulded by day & left over night to harden. The lime is slaked & intimately mixed with sand in proportion of 4-10%. Sand-lime bricks are much stronger than clay bricks & are uniform in color & texture.

Wilma Caldwell
Architectural technologist