This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Within the last few years, the sand-lime brick industry has been developed to some extent. The materials for making this brick consist of sand and lime; and they were first made by moulding ordinary lime mortar in the shape of a clay brick, and were hardened by the carbon dioxide of the atmosphere.
There are two general methods of manufacturing these bricks:
(a) Brick made of sand and lime, and hardened in the atmosphere. This hardening may be hastened by placing the brick in an atmosphere rich in carbon dioxide; or still less time will be required if the hardening is done with carbon dioxide under pressure.
(6) Brick made of sand and lime, and hardened by steam under atmospheric pressure. This process may be hastened by having the steam under pressure.
When sand-lime bricks are made by the first process, it requires several weeks for the bricks to harden; and by the second method it requires only a few hours; the latter method is the one generally used in this country. The advantages claimed for these bricks are that they improve with age; are more uniform in size, shape, and color; have a low porosity and no efflorescence; and do not disintegrate by freezing. The compressive strength of sand-lime brick of a good quality ranges from 2,500 to 4,500 pounds per square inch.