According to the Concrete Society[1], these panels consist of autoclaved aerated concrete (sometimes called Aerated concrete) reinforced to form structural precast units. RAAC are made of the same core material as unreinforced autoclaved aerated concrete – cement, blast furnace slag, pulverised fuel ash or silica flour, and these are mixed with water and aluminium powder – invented in the 1920’s in Sweden, and introduced to the UK in late 1950’s. Concerns over the material and its use started in the 1980’s, as according to the Royal Institute of Chartered Surveyors (RICS)[2], when RAAC planks were not considered durable material and its life expectancy was predicted to be around 30 years by Building Research Establishment (BRE).
As the life span of RAAC is achieving its final expectancy, the government is worried with future failure of panels, exposing risks of collapse and damages. So far, over 150 schools have been identified as containing RAAC, and the minority have a mitigation plan in place.



