Autoclaved aerated concrete is manufactured with the main raw materials of quicklime, cement and siliceous sand. The sand must be finely ground. A proportion of the sand may be replaced with quick ash.
An automated precision.
The ingredients are mixed using a set ratio and then water is added and a mortar mix is created. A small amount of aluminium powder is then mixed into the resulting suspension.
The mortar is poured into a tub (mould), where the metallic, fine particled aluminium develops hydrogen gas in the alkaline mortar mixture. Many small gas bubbles are created, which expand the gradually stiffening mixture. After 15 – 50 minutes, the final volume is achieved and blocks between 3 and 8 metres long, up to 1,5 metres wide and 50 – 80 cm high are produced.
These “doughy” blocks are cut into the required building element sizes with wire. After 8 – 12 hours the aerated concrete attains its final properties via curing in special autoclaves (high-pressure steam boilers) at temperatures of 180 – 200 deg C in steam under saturated vapour pressure of 10 – 12 Bar. The autoclaved aerated concrete corresponds chemically to the mineral tobermorite, which can be found in natural environments. The production takes place in a sealed cycle and this no pollutants to water, air or ground are released. Via the curing with steam, the autoclaved aerated concrete avoids a great deal of potential energy waste.