Reinforced Autoclaved Aerated Concrete (RAAC)

Reinforced Autoclaved Aerated Concrete (RAAC) is a lightweight, precast, cellular concrete building material. It is composed of quartz sand, gypsum, lime, portland cement, water and aluminium powder, cured under heat and pressure in an autoclave. Forms include blocks, wall, floor and roof panels, cladding (façade) panels and lintels.

RAAC was used predominantly in public-sector construction buildings constructed since the mid-1950s. RAAC has been found to have limited structural rebar integrity in 40 to 50 year-old RAAC roof panels, and can be liable to fail without warning, with no visible deterioration.