Small, regular-sized unit, usually of clay but also of calcium silicate (sand and lime) or concrete, used as a building material. See also Conservation for Brick Raw materials for bricks are widespread; the method of manufacture is determined by the physical and chemical properties of the clay and by economic circumstances. Calcium silicate bricks are made of a damp mixture of sand with 10% hydrated lime, formed in a powerful press and steamed in an autoclave for several hours. Concrete bricks (see Concrete, §II, 1) are made from a Portland cement and sand mixture cast in moulds. In the most common format the length is approximately twice the width and three or four times the depth. The size and weight of a brick are such that the bricklayer can pick it up in one hand, although sizes have varied over the centuries. Square blocks and thin, tile-like bricks have also been used. Bricks are used either in massive load-bearing structures or as a thin ...