There are no aggregates and an abundance of voids in RAAC, meaning that it is not as strong as other forms of concrete, is more vulnerable to water ingress and collapses under its own weight due to lack of structural integrity. Additionally, variations in the manufacturing quality of RAAC meant that in some boards, the internal steel reinforcements didn’t reach the end of the board. This means when these boards were laid in place with a support at either end, the only thing holding the weight of the board, as well as any surrounding materials or fittings, was the fragile RAAC itself. As a result, RAAC boards can eventually deform under their own weight due to a lack of structural integrity.
In 2018, RAAC roof boards collapsed in a school in Kent. The collapse occurred over a staff room, not a classroom, at a weekend and no one was injured. However, there have been several more incidents since 2018. These collapses sparked renewed concerns about RAAC structures nationwide.
Now, owners or managers of buildings that may contain RAAC are advised to contact an RAAC surveyor such as EMS to locate any RAAC and advise on the next steps.
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