MPA study finds waste clay and bricks could reduce embodied carbon of cement by 30%

Using waste clay and bricks in the cement production process could reduce the final product’s embodied carbon by as much as 30 per cent, according to a recent report.

Led by the Mineral Products Association (MPA) with funding from Innovate UK, the two-year study found that reclaimed clays and finely-ground brick powder can be used in the manufacture of cement and concrete to lower associated emissions compared with the leading CEM I cement.

The report also found that if calcined clays using these materials are adopted by the UK construction industry, up to 1.4Mt of materials could be diverted from waste streams.

In the UK clay is an abundant material and can offer an alternative to industrial by-products such as ground granulated blastfurnace slag (GGBS) and fly ash, which are commonly used to lower the embodied carbon of cement. The availability of both GGBS and fly ash has been waning in recent years as the power and steel industries decarbonize.

Elsewhere in the world, the use of calcined clays as a secondary cementitious material (SCM) is increasingly common, but until now, they have not been officially tested in the UK.

The study tested two heating methods to prepare the clay for use as an SCM: a traditional rotary kiln and ‘flash heating.’ Both methods were found to produce high-quality calcined clays, and no significant difference was found between the two methods.

The project has received support from Heidelberg Materials UK, Tarmac, Imerys Minerals Ltd, Forterra, University College London, and the University of Dundee.

MPA Executive Director for Energy and Climate Change, Dr Diana Casey, said, “Using brick waste and reclaimed clays will not only lower carbon and reduce waste but also has the potential to create a whole new market if these clays become widely used in the construction industry, helping to retain economic value in the UK, secure jobs, and attract investment.”

The development of low-carbon cements and concretes is one of the seven key levers in MPA UK Concrete’s ‘Roadmap to Beyond Net Zero.’ The roadmap sets out the country’s concrete and cement industry’s own commitments to achieving net zero and builds on its decarbonising of the industry by 53 per cent since 1990.