AAC is a lightweight cellular material which is formed by a chemical reaction between finely divided calcareous and siliceous materials. The calcareous component is usually lime and/or cement. The siliceous component usually consists of natural or ground sand and/or industrial by-products such as slag and pulverized fuel ash (PFA), also known by fly ash. The cellular structure is achieved by either a chemical process causing aeration, or by introducing air voids by mechanical means into a slurry which contains no coarse material The aeration is caused by the addition of a small quantity of acidic aluminium paste that reacts with the alkaline lime &; cement to expand the mixture.
This reaction causes the release of hydrogen gas and the formation of tiny, finely dispersed bubbles. The hydrogen dissipates after the reaction process leaving the air filled bubbles. After mixing, the slurry is placed in a mould for curing. For products that require reinforcing, the corrosion protected steel reinforcing mesh is placed in the mould before the slurry is added. After a few hours curing the product is firm enough to be removed from the moulds and transported to a cutting machine where it is cut precisely into the required sizes. Waste material is recycled back for crushing and remixing.