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Structural safety of reinforced autoclaved aerated concrete (RAAC) planks

Region: CROSS-UK


A small sample of reinforced autoclaved aerated concrete (RAAC) showing a bubbly cross-section.

This Theme Page has been created to raise awareness of and encourage knowledge sharing on the structural safety of reinforced autoclaved aerated concrete (RAAC) planks.

It also acts as a knowledge hub for safety related information on RAAC planks.

 

What is RAAC?

Autoclaved aerated concrete (AAC) is different from normal dense concrete. It has no coarse aggregate, and is made in factories using fine aggregate, chemicals to create gas bubbles, and heat to cure the compound. It is relatively weak with a low capacity for developing bond with embedded reinforcement.

When reinforced (RAAC) to form structural units, the protection of the reinforcement against corrosion is provided by a bituminous or a cement latex coating. This is applied to the reinforcement prior to casting the planks. The reinforcement mesh is then introduced into the formwork and the liquid AAC mix added.

 

RAAC roof collapse

In late 2018, the Local Government Association (LGA) and the Department for Education (DfE) contacted all school building owners to draw attention to a recent failure involving a flat roof constructed using RAAC planks. There was little warning of the sudden collapse.

 

Share your knowledge of RAAC

Your report will make a difference. It will help to create positive change and improve safety.

Our secure and confidential safety reporting system gives professionals the opportunity to share their experiences to help others.


RAAC knowledge hub

This knowledge hub presents safety related information on RAAC planks from CROSS and third party organisations.

Failure of reinforced autoclaved aerated concrete (RAAC) planks

In late 2018, the Local Government Association (LGA) and the Department for Education (DfE) contacted all school building owners to draw attention to a recent failure involving a flat roof There was little warning of the sudden collapse.

IStructE RAAC Study Group & members with RAAC experience

The IStructE have formed a RAAC Study Group and created a list of professionally registered structural engineers who have experience of providing solutions for managing RAAC planks.

Failure of RAAC planks in schools

A reporter was asked to investigate a reinforced autoclaved aerated concrete (RAAC) roof which had collapsed in a school.

Reinforced autoclaved aerated concrete roof planks - sharing experiences

A reporter has surveyed a number of buildings with reinforced autoclaved aerated concrete (RAAC) roof planks and wants to share their experiences to help others.

Reinforced autoclaved aerated concrete in roofing in schools

This document is for building owners to help them to identify the presence of reinforced autoclaved aerated concrete (RAAC) and to check whether any further investigation or action is needed.

Aerated concrete slabs

A reporter discusses the failure of precast reinforced autoclaved aerated concrete (RAAC) slabs during construction.

Share your knowledge

Your report will make a difference. It will help to create positive change and improve safety.

Our secure and confidential safety reporting system gives professionals the opportunity to share their experiences to help others.