What is Raac? Pupils in schools affected by concrete should get 10% exam boost, says report

Remedial work being carried out at a school that has been affected by Raac  (Jacob King/PA)
Remedial work being carried out at a school that has been affected by Raac (Jacob King/PA)

Pupils at schools in England that have had to close because of dangerous concrete should get an increase of up to 10 per cent in their exams, says a report on the impact of Raac. 

More than 150 schools were forced to partly or fully close in September after being found to have reinforced autoclaved aerated concrete (Raac), a commonly used building material that is at risk of collapsing in some cases.

Exam boards have so far refused to make exceptions for pupils at affected schools who are sitting GCSE and A-level exams this summer despite serious disruption to teaching.

Professors at Durham University said exam boards should compensate for the "lost learning" of pupils.

The report urged ministers, together with exam boards and the exam regulator, Ofqual, to make a plan to "relieve the anxiety of students in the school and others like it" and offer them "qualification outcomes equivalent to what would have happened in the absence of the crisis".

The study is based on St Leonard’s Catholic School in Durham, one of the highest performing state schools in the North-East at GCSE level, which had to scrap teaching plans at the start of the academic year in September due to the presence of Raac.

The report found that the school had to shut at very short notice in September, with no teaching at all taking place in the first week. Students then had a period of online lessons, with a slow resumption of face-to-face classes in often cramped conditions. Years seven and eight have been taught at Ushaw College, which is a four-mile bus trip away.

The study's authors, professors Stephen Gorard and Nadia Siddiqui, from the university's Evidence Centre for Education, said: "The Department for Education could perhaps direct that something like this takes place as part of their package of measures to help those few schools faced with the worst of the RAAC crisis."

Amid all of this, many have found themselves unsure about what Raac is and when it was used in construction. Here is a comprehensive look at Raac.

What is Raac and why was it used?

Raac stands for reinforced autoclaved aerated concrete. It is a lightweight building material that is mostly used in flat roofing, and sometimes in floors and walls.

It has an aerated, bubbly texture and was preferred as a cheaper alternative to standard concrete as it was faster to produce and easier to install. The air bubbles in Raac mean it is lighter and can provide good thermal insulation. However, the speed and ease come at a cost. Raac is less durable and its lifespan is only around 30 years.

Plus, if it is exposed to moisture, it is prone to collapse, as the bubbles can allow water to enter the structure.

How is Raac made?

According to the Standing Committee on Structural Safety (Scoss), Raac is structurally different from concrete because of the way it is made.

Scoss said: “Although called “concrete”, [Raac] is very different from traditional concrete and, because of the way in which it was made, much weaker.

The Trades Union Congress explained that Raac is manufactured by mixing raw materials before pouring the mixture into a mould. A high-pressure autoclaving process – which essentially means exposing it to steam and pressure – is then used to create RAAC. This results in air bubbles forming in the structure.

When was Raac used in buildings?

Reinforced autoclaved aerated concrete was used in construction between the 1950s and the 1990s.

The risks of Raac aren’t a new discovery. Raac’s differences from traditional concrete were outlined in the 1960s. And, in the 1980s, a report by the Institution of Structural Engineers revealed that short-term exposure to moisture reduced the material’s strength by around 13 per cent, while long-term exposure to air pollution reduced it by 40 per cent.

A 1996 government-funded report by the Building Research Establishment also found that Raac panels had been cracking in a housing development, and there were cracks and bends in panels installed in schools.

In 2003, a Labour government aimed to refurbish all of England’s secondary schools but in 2010 the Tories dropped the project as not cost-effective.

The Government concluded that while there were no immediate safety risks, Raac panels should be inspected every year.