Since the UK government ordered the immediate closure of over 100 school buildings just days before the start of the autumn term mounting pressure to identify all other buildings that may be affected has been rising. The reason for these closures is the presence of reinforced autoclaved aerated concrete (RAAC), a lightweight material used to construct these schools between the 1950s and 1990s. This material, now past its 30-year design life, has raised serious concerns about the safety of school buildings and other structures such as hospitals
Reinforced autoclaved aerated concrete (RAAC) is a cementitious material used extensively in roof structures due to its lightweight nature and thermal insulation properties. However, it has a limited lifespan of 30 years. In buildings with an RAAC presence, structural problems began to emerge in the 1990s. Reinforced autoclaved aerated concrete (RAAC) has a compressive strength of just 2-5N/mm, making it much weaker than conventional concrete. It is porous, and this porosity can lead to reinforcement corrosion, especially if the roof develops a leak and allows water to permeate to the RCC materials. RAAC is also prone to cracking due to moisture and temperature-related movement. This can result in water ponding on the roof. RAAC planks can act independently and have limited load-sharing capabilities with neighbouring panels.
The Department of Education (DfE) has received warnings about RAAC for years. This summer, some "new evidence" emerged, leading to the sudden decision to close affected school buildings. Schools minister Nick Gibb explained that surveys during the summer revealed that RAAC, previously considered low risk, had been proven to be unsafe. A beam that showed no external signs of risk had collapsed, prompting the DfE to take swift action.
Currently, 156 schools have been confirmed to contain RAAC, with 52 identified as having critical risks. They have implemented safety measures. Initially deemed non-critical, the remaining 104 school buildings have been instructed to be vacated and restricted until mitigations are in place. However, the reinforced autoclaved aerated concrete (RAAC) issue isn't confined to schools. It was used in various building types, including hospitals and public sector structures. This is causing concern among the affected parties and the government.
A key player in this crisis, the construction industry has raised several concerns about RAAC concrete. Major contractors say the government has not contacted them for emergency remediation work or rebuilding jobs. The government and the construction industry are just beginning to grasp the scale of the situation. The role of modern construction methods (MMC), particularly in building temporary structures as stop-gap arrangements, is uncertain. The government's previous experience with modular school construction has been a mixed bag. Capacity and labor shortages in the construction industry pose significant challenges. The ongoing activities and limitations of the industry complicate a quick-fix solution.
Opposition parties, such as Labour, immediately called for transparency, urging the government to release a list of schools affected by reinforced autoclaved aerated concrete. Labour also questioned the delay in issuing guidance. From a legal perspective, liabilities arising from RAAC-related incidents could be substantial, with complexities regarding responsibility for material failures or incidents. The lack of transparency in reporting has left parents uncertain about their children's safety.
What are the next steps in the RAAC concrete crisis?
The RAAC school crisis has highlighted the vulnerability of buildings constructed with this material. It has raised questions about accountability, transparency, and the capacity to address a widespread issue with far-reaching implications. As the understanding of RAAC continues to evolve, the need for a coordinated approach among various stakeholders becomes increasingly apparent. The construction industry, in particular, must navigate capacity and labour shortage challenges while addressing the urgent need for repairs and safety assessments.
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