AAC Technology - Plants and Systems - HESS Group

The Autoclaved Aerated Concrete (AAC) materialwas developed in 1924 in Sweden. It has becomeone of the most used building materials in Europeand is rapidly growing in many other countriesaround the world.Autoclaved Aerated Concrete, also known asAircrete, is a lightweight, load-bearing, highinsulating,durable building product, which isproduced in a wide range of sizes and strengths.AAC offers incredible opportunities to increasebuilding quality and at the same time reduce costsat the construction site.AAC is produced out of a mix of quartz sand and/or pulverized fly ash (PFA), lime, cement, gypsum/anhydrite, water and aluminium and is hardenedby steam-curing in autoclaves. As a result of itsexcellent properties, AAC is used in many buildingconstructions, for example in residential homes,commercial and industrial buildings, schools,hospitals, hotels and many other applications.The construction material aircrete contains 60%to 85% air by volume. The solid material part isa crystalline binder, which is called Tobermoriteby mineralogists. Besides the binding phaseTobermorite aircrete contains grains of quartzand in minor amounts some other minerals. Thechemical composition of Tobermorite showssilicium dioxide, calcium oxide and water.The silicium dioxide is obtained from silica sand,fly ash (PFA), or crushed quartzite. It is possible toobtain silicium dioxide as a by-product from otherprocesses, e.g. foundry sand. The calcium oxide isobtained from quick lime, hydrated lime and cement.Gypsum/Anhydrite is added in small quantitiesas a catalyst and for optimizing the propertiesof AAC. Aluminium powder / paste is used as expandingagent.