Forterra, a leading manufacturer of concrete and clay building products, has recently established an exciting partnership that reduces carbon emissions while making a substantial contribution to the UK’s circular economy through the innovative reuse of its manufacturing waste.

Taking a major step forward in its sustainability journey, Forterra has partnered with LKAB Minerals, part of the international mining and minerals group LKAB, to pioneer the repurposing of crushed brick waste to produce calcined clay as a low-carbon alternative to traditional cement.

Derived from recycled brick waste, calcined clay can be used as a cement replacement, known as a Supplementary Cementitious Material (SCM) in accordance with the cement standards. It brings a number of advantages, the most important of which is that SCM contributes to the concrete’s strength by increasing the strength-producing compounds and in doing so reducing the porosity of the concrete.

Conventionally, calcined clay is produced by heating raw clay at temperatures of between 700-800°C to drive off volatile compounds like water and carbon dioxide – a process called calcination. However, the combustion process is emissions heavy, resulting in high embodied carbon. What is novel about Forterra’s approach is that it avoids the high-temperature calcination process: the waste bricks have already been fired and the carbon accounted for. The embodied carbon of the final product is significantly reduced, and the entire process contributes towards a circular economy.

Calcined clay production from brick waste

To produce the calcined clay product, brick waste from Forterra’s Kings Dyke factory is crushed and delivered to LKAB Minerals, who then fine-mill the waste to an agreed specification, processing it into a reactive calcined clay material. Initial use of the calcined clay at one of Forterra’s aggregate block plants in 2024 has resulted in a significant emissions avoidance of approximately 2,000 tonnes of CO2.

Forterra and LKAB Minerals will collaborate to manufacture approximately 35,000 tonnes of calcined clay per year, applying the circular economy principles of reuse and repurpose to these waste materials, making a significant contribution towards the construction industry’s carbon challenge.

Further information can be found here: https://www.forterra.co.uk/sustainability/