What is RAAC Concrete? (The Risks & Government Initiatives)

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September 3, 2024

RAAC & Its Composition

RAAC (Reinforced Autoclaved Aerated Concrete) is a lightweight and durable quality concrete used in buildings constructed between the 1950s and 1990s. It is composed of cement, lime, sand, and water, which form a slurry upon mixing, to which aluminium powder is added. The reaction of aluminium powder with the other components leads to hydrogen gas production and thousands of tiny air pockets, giving RAAC an aerated form.

The mixture is then poured into the moulds and left to rise. Once the material has risen enough, it is cut into blocks or panels and left to cure in autoclaves under high-pressure steam. This process results in the formation of highly strengthening material.

This guide helps you know about the applications of RAAC and the potential risks associated with using RAAC concrete in different buildings. It also includes detailed information about the Government initiatives taken in this regard and the responsibility of building or estate owners to mitigate the risks of RAAC concrete with proper management.

Applications of RAAC

This type of concrete is usually found in floors, roofs, and walls of commercial and residential buildings. It is a highly energy-efficient material that helps to enhance the insulation of properties, contributing to a reduction in cooling and heating energy bills. RAAC concrete is also resilient to fire and pests, which has made it a popular material used in the construction of various public sector properties, such as hospitals and schools in the UK.

RAAC plank is a pre-cast and reinforced form of RAAC that has been particularly popular for its structural strength. This reinforced material is made by using steel mesh or similar materials and has been widely used in the construction of various structures due to its lightweight properties.

Potential Risks Associated With RAAC

Recently, it has been identified that RAAC concrete can develop crumbles over time and is prone to collapsing. This material is also susceptible to moisture absorption, leading to mould growth if the sealing is improperly done.

This discovery has led to unrest in the country, with expert suggestions to get all the government and private buildings checked to ensure their safety and structural integrity. The LGA (Local Government Association) has advised its members to ensure immediate checking of the building claddings, floors, roofs, and walls for RAAC in their respective estates. Moreover, the DfE has been notified of further sudden collapses of roof panels, which seemed to be in good condition and were constructed with RAAC concrete.

Due to its lightweight nature and distinctive porous structure with numerous tiny air pockets, this material can be easily identified and distinguished from other types of concrete.

Initiative Taken by the UK Government

The UK Government has been aware of RAAC’s potential vulnerability since the 1990s. Since 2018, it has worked in close collaboration with the Welsh Government and other devolved governments to efficiently manage the RAAC implications for different building structures.

2018

In December, the DfE (Department for Education) and the LGA (Local Government Association) warned building owners about the failure of a building component constructed using RAAC.

2019

In May, an alert was raised by the SCOSS (Standing Committee on Structural Safety), which highlights the construction of a school’s panel roof with RAAC and emphasises the associated risks.
In November, the NWSSP (NHS Wales Shared Services Partnerships) notified the NHS organisations working in Wales about the risks associated with RAAC planks.

2020

In February, the WLGA (Welsh Local Government Association) informed the local authorities about the potential issues of RAAC concrete after SCOSS published an alert in 2019.

2022

After the completion of building reviews, a specialist structural engineer was appointed in November. This engineer was responsible for reviewing the reports and locations where RAAC had been found.

2023

In September, several updates about the RAAC were introduced in the education establishments in Wales, the Welsh public estate, the education department, and across NHS Wales.
Moreover, the first minister’s press conference was also held, and the Minister for Education and the Welsh Language made an oral statement regarding RAAC in the education sector.
In February, the specialist structural engineer recommended providing further notice to the NHS to assure the NWSSP and the Welsh Government that comprehensive assurance surveys and examinations are being conducted.
The Welsh Government, the WLGA, and the local authorities have collaborated closely since March 2023.
Several local authorities have completed the school estate reviews, and several reviews are underway.
The Welsh government commissioned a condition and energy survey for all state-funded educational institutes, including schools and colleges, in May 2023. This survey would help highlight the RAAC-containing structures so that specialist structural engineers can perform further inspections.
In August, the Welsh Government forwarded the request to public sector building owners, estate owners, and other responsible bodies for premises’ management. This request was to commission the urgent new surveys of public sector buildings, including schools. This step was taken after the emergence of various RAAC incidents in education settings during the summer period, which the UK Department reported for Education.

The Responsibility of Building or Estate Owners

Ensuring the safety of buildings, employees, pupils, tenants, and public members lies on the building or estate owners and those responsible for premises management. The duty of care owed by the builder and their sub-contractors towards a property’s occupiers and that of the landlords and building owners towards the tenants and third parties who could get injured in case of property failure has been established in the Defective Premises Act 1972 and the Building Safety Act 2022.

Therefore, building owners must identify the presence of RAAC concrete in their properties and ensure the implementation of all the required measures for identifying, assessing, and mitigating the potential risks of RAAC concrete. They can also decide to restrict access or close an area where RAAC has been identified to ensure the safety of occupiers.

In this regard, they can get help from the HSE (Health and Safety Executive) webpage regarding proper risk management from RAAC concrete. Additionally, the Institute of Structural Engineers offers comprehensive guidance on investigating and assessing the presence of RAAC, along with advice on the critical risk factors associated with RAAC panel construction. It also classifies the risk factors and describes their impacts and required remedial work to ensure proper risk management.