“Sparkling” concrete, pioneered in Sweden, swept Europe in the middle of the last century. Known as ‘aerobar’, ‘aircrete’ and Raac (reinforced autoclaved aerated concrete), this lightweight, cheap alternative to traditional concrete mixes was used in thousands of British public buildings between the 1950s and 1990s. In the 1980s, the system began to fall into disrepair and buildings had to be demolished. This is a timeline of who knew what and when.
1980s – With an estimated lifespan of 30 years, failures of Raac roof panels on 1950s buildings were inevitable. Engineers also discovered that some panels were too thin for the distance they were expected to span, that some lacked enough steel to anchor them to vertical structures, and that leaking roofs triggered a “rapid worsening” of corrosion. steel.
1996 – The UK’s Building Research Establishment (BRE), a government executive agency, published an “information paper” on Raac concrete roof boards installed before 1980, which warned of “warping and excessive cracks. There was no evidence ‘so far’ to suggest they posed a safety risk to building users, but it was stated that Raac could not have a useful life much longer than 30 years. It has been proposed to remove reference to Raac from the British Standard for Structural Concrete because it gives it “unwarranted respectability” and “the impression that it can be used for permanent structures”.
1999 – The Standing Committee on Structural Safety (SCOSS), chaired at the time by the eminent chemist Jack Lewis, a peer of his, urged those responsible for schools with pre-1980 Raac plank roofs to arrange inspections. The threat level appears low and a report from the professional body for engineers states that “generally speaking, the deterioration of the Raac planks does not endanger structural safety”. He also warned: “Complacency can prevent recognition of growing risks. »
2002 – The BRE, now privatized but still working in close collaboration with the government, issued a study of the “rather mixed” behavior of Raac which highlighted “excessive deformations in service and cracks” in buildings before 1980.
July 2018 – A period of calm over the Raac risk ended when the ceiling of the staff room at Singlewell Primary School in Gravesend, Kent, collapsed on a Saturday evening after showing signs of structural stress the day before. No one was injured, but images of the destroyed room suggest people could have died. The school was rebuilt in 1979 thanks to Raac after a fire.
December 2018 – The Department for Education (DfE), then led by MP Damian Hinds, joined forces with the Local Government Association to contact all school building owners in England about the collapse in Kent. They advised them to “urgently check” the roofs, floors, cladding or walls in Raac. Schools were told that two recent failures meant the working hypothesis that Raac boards adequately warned of failure due to visual deterioration “could no longer be reliable”.
2019 – The Ministry of Defense (MoD) has issued its own alert to staff on UK estates, highlighting the school collapse, which was preceded by “little or no warning”. It also highlighted a partial collapse of a store.
May 2019 – SCOSS delivered an alert for departments, councils, NHS leaders and construction professionals, highlighting the “significant risk” of Raac failing. “We must not lose sight of the fact that the collapse of 2018 was sudden and with very little discernible warning,” he said. A study group from the Institution of Structural Engineers (IStructE) was commissioned to investigate.
April 2020 – SCOSS published Findings from building surveys revealed that the Raac beams were noticeably suffering from water ingress, cracking, spalling and surface corrosion. The expert who assessed the buildings said they “required rectification” but there was no “increased risk of sudden shear failure”.
February 2021 – The DfE has published a Raac guide for the education sector in England. In the same year, the Cabinet Office’s real estate team published a formal notice emphasizing that Raac was “now dead and likely to collapse”.
March 2022 – Raac problems aside, the demand for money to rebuild crumbling schools in England has far outstripped the funds available. This month, 1,105 projects were nominated for funding, but only 61 were successful. In 2021-22, the DfE’s capital expenditure was around £4.9 billion, lowest recorded since 2009-10. IStructE said the 1960s and 1970s Raac had “structural deficiencies”, citing “sudden panel failure”. Amid growing concern, the DfE has published a questionnaire asking schools, councils and academies about Raac in their buildings.
September 2022 – the property arm of the Cabinet Office told all Whitehall property leaders: “Raac has now expired and is likely to collapse. »
October 2022 – Education Minister Lady Barran for follow-up City councils across England have received their responses to the March questionnaire, saying it is “of the utmost importance” and that buildings bearing the Raac must be monitored “to ensure they remain safe”.
December 2022 – The DfE annual report clearly warned: “There is a risk of one or more blocks collapsing in some schools. »
March 2023 – The Defense Ministry has given the military until the end of July to check Raac’s buildings in British defense, with fixes due to be made by December. Loughborough University, which was previously commissioned to investigate Raac for NHS England, said seven health trusts had buildings mainly constructed in RAAC.
May 2023 – The DfE identified that Raac may have been present in 572 schools in England, but that at that stage more than 8,000 schools had not been checked.
August 2023 – The Health and Safety Executive announced: “Raac is now expired for life. It is likely to collapse with little or no notice.
Source link: https://www.theguardian.com/uk-news/2023/sep/04/raac-crisis-who-knew-what-when-crumbling-concrete-england
