Waste clay and bricks cut carbon in cement and concrete
New research confirms UK reclaimed clay and bricks cut carbon emissions in cement and concrete
USING waste clay and bricks in cement production could reduce the material's embodied carbon by up to 30% and boost UK construction’s circular economy, according to a new report.
A two-year study led by the Mineral Products Association (MPA) with funding from Innovate UK has demonstrated that UK reclaimed clays and finely ground brick powder can be used as calcined clays in cement and concrete manufacturing to deliver lower emissions compared with the market-leading CEM I cement.
The findings also confirmed that, if adopted by the UK construction industry, calcined clays from these sources have the potential to divert 1.4 million tonnes of material from waste streams.
Clay is a naturally abundant material in the UK and can offer an alternative to industrial by-products such as ground granulated blast-furnace slag (ggbs) and fly-ash which have traditionally been used to lower the embodied carbon of cement. UK production of both materials is reducing as the power and steel industries decarbonize.
In other parts of the world, calcined clays are used as a secondary cementitious material, but until now they have not been officially tested in the UK.
Two heating methods were trialled to prepare the clay for use in cement and concrete: commonly used rotary kilns, and the more innovative ‘flash heating’. Both methods have been shown to produce high-quality calcined clays, with no significant difference between techniques.
The project has been supported by Heidelberg Materials UK, Tarmac, Imerys Minerals Ltd, Forterra, University College London, and University of Dundee.
Dr Diana Casey, executive director for energy and climate change at the MPA, 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 represents one of seven key levers in MPA UK Concrete’s ‘Roadmap to Beyond Net Zero’. The roadmap sets out the UK concrete and cement industry’s own commitments to delivering net zero and builds on its decarbonizing the industry by 53% since 1990.
To read the full report on the MPA website, click here.
