The shift to clean energy threatens essential low-carbon cement alternatives like fly ash and ground granulated blast-furnace slag (GGBS), which are by-products of fossil fuel use. These materials have been crucial for reducing concrete’s carbon footprint, particularly GGBS in major construction projects. As the construction industry seeks to lower cement usage due to its significant carbon emissions, the availability of these sustainable supplementary cementitious materials (SCMs) is predicted to decline. Professor Leon Black from Leeds University highlights that the decarbonization of electricity and the transition of UK steel production to electric recycling methods will make these SCMs increasingly scarce, posing challenges for future sustainable construction efforts
UK clay as an alternative to traditional SCMs
The Concrete Centre is addressing the potential shortage of sustainable cement alternatives by exploring UK clays as alternative supplementary cementitious materials (SCMs) through the Eureka project, funded by the Engineering and Physical Sciences Research Council (EPSRC). Led by Professor Leon Black, alongside Professor Hong Wong from Imperial College London and Clive Mitchell from the British Geological Survey, the team is investigating the viability of lower-grade clays as substitutes for metakaolin, which is costly and derived from china clay. Professor Black emphasizes that these clays could have significant applications beyond landscaping, potentially enhancing the sustainability of concrete production.
BGS maps clay distribution for Eureka Project
The British Geological Survey (BGS) is vital in mapping suitable clays across the UK, having analyzed around 60 samples and identified about a dozen with promising properties. For clays to be viable as supplementary cementitious materials (SCMs), they must undergo calcination, which involves heating the clay to approximately 800°C to enhance its reactivity. Although this process has a carbon cost, it is much lower than that of traditional cement production. Professor Black highlights the environmental advantages, noting that calcined clay could reduce carbon emissions to about half that of Portland cement, significantly benefiting the construction industry’s overall environmental footprint.
Optimising clay processing for concrete industry
The Eureka project aims not only to identify suitable clay sources but also to optimize their application in concrete production. After calcination, the clay is milled into a fine powder, which can lead to flow issues in concrete mixtures. To tackle this, the research team is collaborating with additives suppliers to enhance the performance of calcined clay while maximizing cement replacement without compromising quality. Professor Black emphasizes the need for practical applications that meet industry standards, and the team is engaging with industry partners throughout the supply chain. Promising laboratory results have emerged, and the next step involves real-world testing, with expectations to have the first batches of calcined clay ready for industry evaluation by the year’s end.
