Gas Concrete

a variety of cellular concrete; made by injecting a gas-forming agent (usually aluminum powder) into a mixture consisting of a binding component (such as portland cement or milled quicklime), a siliceous component (milled quartz sand), and water. The gas-forming process takes place as a consequence of the chemical reaction between the calcium hydroxide and the aluminum; the hydrogen that escapes during this reaction causes a foaming up of the solution, which then hardens, retaining a porous structure. For quick hardening and production of items made from gas concrete with the necessary strength factors, the products are subjected to heat and moisture treatment in autoclaves at a steam pressure of not less than 9 atmospheres and a temperature of 175° C.

Gas concrete is used chiefly as a heat insulating material, especially in construction during the fabrication of the outer enclosure of buildings. The density of gas concrete is 300, 400, 500, 600, and 700 kg/m³; its compressive strength is 0.8, 1.2, 2.5, 3.5, and 5.0 meganewtons per sq m (8, 12, 25, 35, and 50 kg per sq cm), respectively. There are a number of varieties of gas concrete, which differ according to the type of cementing or siliceous material used: for example, gas silicate (cementing component, quicklime), gas-cinder concrete (siliceous component, cinders from a heat and electric power plant).