New concrete recipe to help decarbonisation

Changes to the standard for concrete have been published by BSI, the business improvement and standards company, and could save 1 million tonnes of carbon dioxide emissions each year – the equivalent of more than 3,500 transatlantic flights – if the changes are adopted across all UK construction sites.

The new concrete ‘recipe’ blends finely ground limestone from UK quarries with other materials such as fly ash, a by-product from power generation, and ground granulated blast furnace slag (ggbs), a by-product from the steel industry.

UK Concrete and cement manufacturing accounts for 7.7 million tonnes of carbon dioxide emissions, equating to 1.5% of the UK’s total carbon emissions.

Most carbon dioxide emissions are associated with the production of cement, and using these supplementary materials, such as limestone powder, helps to reduce the amount of traditional cement (CEM I) to create a lower-carbon concrete.

With the new standards now available, the CEM I content in concrete can be replaced with up to 20% limestone powder, a product widely available in the UK.

For every 5% of limestone powder added, a 5% carbon dioxide reduction can be delivered per tonne of concrete, according to MPA UK Concrete, the group representing the UK concrete industry.

‘Making concrete is a bit like baking except that with concrete, ingredients are combined to alter properties such as strength, deliver environmental performance, and change the aesthetics of the finished material,’ said Elaine Toogood, director of architecture and sustainable design at the Concrete Centre.

‘In a climate emergency, this new approved standard is important in helping architects and engineers significantly lower embodied manufacturing emissions today and in the future, while delivering structural strength in buildings and infrastructure.

‘Providing a new generation of concretes is an important part of the UK concrete and cement industry’s roadmap to net zero alongside other technologies including the use of decarbonized transport, fuel switching, and carbon capture, usage or storage (CCUS) technology.’

For many years, ggbs and fly ash have been repurposed as an ingredient for concrete, but less of it is being produced in the net-zero transition, so the use of limestone fines is important for helping to provide a sustainable source of materials to continue to lower the embodied emissions of concrete.

The new specification changes are part of a rigorous research and testing process over two years, with the results then independently assessed for inclusion into the standard by the BSI technical committee for concrete.

The concrete and cement industry has a strong track record of decarbonisation, having already delivered a 53% reduction in absolute carbon emissions since 1990, and is, as a whole, decarbonizing faster than the UK economy.