Engineered UK clays for production of low-carbon cements

Supplementary Cementitious Materials (SCMs) used to produce low-carbon concrete in the UK are facing increasing supply restrictions. High-kaolinite clays, used to produce calcined clay SCMs, in the UK occur in southwest England, well away from the major construction centres. The potential for low-kaolinite clays to produce SCMs is of great interest to the UK construction and minerals sectors. The research project, Engineered UK clays for production of low-carbon cements (informally known as EUREKA), aims to identify sources of low-kaolinite, clay-rich lithologies across the UK that have potential for use as SCM. Clay was identified and sampled from boreholes, brickworks, cement works, hard rock quarries, infra-structure developments, and sand and gravel pits across the UK. These included mudstones, shales, intrabasaltic palaeosols and glacial sediments. Total clay, carbonate and kaolinite contents were used to screen the clays for potential cementitious reactivity. Shortlisted clay resources will be taken forward for larger scale calcination trials and concrete testing. Prelim-inary results of a Life Cycle Assessment indicate that substitution of cement clinker by 30% would require around 2.8 million tonnes of clay to be extracted and calcined; increase that substitution to 50% and this increases to around 4.6 million tonnes of clay. In 2023, 3.4 million tonnes of clay were produced in the UK mainly for brick and tile production. The UK clay in-dustry would, therefore, need to significantly increase production to meet the need to produce calcined clay for use as SCM.