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Reinforced Autoclaved Aerated Concrete (RAAC)

Reinforced Autoclaved Aerated Concrete (RAAC) panels are widely used in mainland Europe and less so in the UK.

These panels consist of autoclaved aerated concrete (sometimes called Aerated concrete) reinforced to form structural precast units. This form of concrete (really an aerated silica product) provides little protection to the corrosion of embedded metal and therefore a bituminous or cement latex coating is applied to the reinforcement as protection. It is typically used for walls, floor planks and roof planks.

Pre-1980 RAAC roof planks are now past their expected service life, there have been some failures and a safety alert has been issued by the Collaborative Reporting for Safer Structures (CROSS). The Institution of Structural Engineers provides the latest guidance: https://www.istructe.org/resources/news/istructe-statement-reinforced-autoclaved-aerated-c/

Further information is available in:

1. IP 10/96 - Reinforced autoclaved aerated concrete planks designed before 1980, BRE, 1996.

2. IP 7/02 - Reinforced autoclaved aerated concrete planks - test results, assessment and design, BRE, 2002.

3. Twelfth Report of SCOSS, Structural-Safety, 1999.

4. BS EN 12602: 2016 Prefabricated reinforced components of autoclaved aerated concrete

RAAC plank failure

RAAC section; image from CROSS

Acknowledgement: Concrete Society