How RAAC Came to be and when the Concrete was used for constructions.

Department for Education Reveals Extent of RAAC Issue

The Department for Education (DfE) has recently disclosed that a total of 147 schools across the UK have been impacted by deteriorating reinforced autoclaved aerated concrete (RAAC). This includes over 10 schools in London. The revelation has raised significant concerns about the safety and durability of structures built with this material.

Funding for Repairs Allocated from DfE’s Capital Budget

In response to the crisis, Treasury officials have confirmed that funds for repairing RAAC-affected buildings will be sourced from the Department for Education’s current capital budget. Chancellor Jeremy Hunt has moved quickly to reassure parents and the public, stating that the government is committed to “spending what it takes” to rectify the issue. However, questions linger regarding the extent of the damage and the financial implications of these repairs.

Calls for Clarity and Urgent Audit

Amid growing concerns, there have been calls for the government to provide clarity on the impact of RAAC usage in hospitals and other public buildings. The Labour Party has urged an “urgent audit” to assess the situation comprehensively.

Investigation into RAAC Usage in Parliament Construction

A separate investigation has been initiated to determine whether RAAC was employed in the construction of the Houses of Parliament, adding another layer of complexity to the issue.

Understanding RAAC: What It Is and Why It Was Used

RAAC Defined

Reinforced Autoclaved Aerated Concrete (RAAC) is a lightweight building material primarily used in flat roofing, with occasional applications in floors and walls. It distinguishes itself with its aerated, bubbly texture. RAAC gained popularity as a cost-effective alternative to traditional concrete due to its faster production and easier installation. Notably, the air bubbles within RAAC contribute to its lightweight properties and provide thermal insulation. However, these advantages come at a cost, as RAAC is less durable with a lifespan of only around 30 years. Moreover, exposure to moisture can lead to structural collapse, as the air bubbles can allow water infiltration.

RAAC Manufacturing Process

RAAC differs structurally from conventional concrete due to its manufacturing process. Raw materials are mixed and poured into molds, followed by a high-pressure autoclaving process that involves exposure to steam and pressure. This process results in the formation of air bubbles within the material.

A Historical Perspective: RAAC Usage and Risks

RAAC in Construction (1950s-1990s)

RAAC was actively used in construction projects from the 1950s to the 1990s, during which time it gained popularity as an economical choice.

Early Awareness of RAAC’s Differences (1960s)

Concerns about RAAC’s structural differences compared to traditional concrete were raised as early as the 1960s.

Reports of Reduced Strength (1980s)

In the 1980s, a report by the Institution for Structural Engineers highlighted that short-term exposure to moisture could decrease RAAC’s strength by around 13%, while long-term exposure to air pollution could reduce it by as much as 40%.

Cracks and Bends in Panels (1996)

In 1996, a government-funded report by the Building Research Establishment discovered cracks in RAAC panels in a housing development, along with cracks and bends in panels installed in schools.

Government Response (2003-2010)

In 2003, a Labour government initiated a project to refurbish all secondary schools in England, but this was discontinued in 2010 by the Conservative government, citing cost-effectiveness concerns. It was concluded that while there were no immediate safety risks, RAAC panels should be inspected annually.

The ongoing issues with RAAC have raised serious questions about its use in construction and the long-term implications for public safety and infrastructure maintenance.

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