As a building material, it was typically used as a lightweight and less expensive alternative to more conventional forms of reinforced/precast concrete, although both by definition contained metal bars, rods, or wire embedded in their structure to improve tensile strength.
Primarily used for floor, roof, and wall construction in the UK since the 1950s, issues with the integrity of the product were flagged in the 1990s. These concerns have come to a head over recent weeks and, as a result of the health and safety implications, a plethora of guidance and information produced.
The HSE has information in the education section of its website, stating:
“Owners or managers of estates should identify reinforced autoclaved aerated concrete (RAAC) in your education setting and seek specialist advice to assess it and develop management plans.
RAAC is a lightweight form of precast concrete, frequently used in public sector buildings in the UK from the mid-1960s to the mid-1980s. It is mainly found in roofs, although occasionally in floors and walls. It is less durable than traditional concrete and there have been problems as a result, which could have significant safety consequences.
RAAC is now life-expired. It is liable to collapse with little or no notice.
If you are responsible for the management, maintenance, or alteration of central and local government buildings you should know whether your buildings contain RAAC, and act appropriately to ensure that such buildings are safe.”
Risk from reinforced autoclaved aerated concrete (RAAC) - Education - HSE
There are also links to other sources of information and advice, including:
Reinforced autoclaved aerated concrete: identification guidance - GOV.UK (www.gov.uk)
Office of Government Property: RAAC Safety Briefing Notice | Local Government Association
While the focus currently is on public sector buildings, it is not clear to what extent this material may or may not have been used in the corporate property sector or independent school sectors. The advice provided though would be generally relevant to all buildings likely to contain RAAC:
- When the presence of RAAC is confirmed, a structural assessment should be carried out.
- Assessment of RAAC is a highly specialised area within the structural engineering profession, and it is important to make sure that those providing structural engineering services are suitably qualified and can demonstrate an appropriate level of skill and experience.
- The Institution of Structural Engineers https://www.istructe.org/ is the main professional body for structural engineers in the UK and maintains a register of engineers with experience in RAAC.