Construction projects could soon be using the world’s first zero emissions cement, thanks to Cement 2 Zero (C2Z), a UK-based demonstrator project bringing together Cambridge University scientists with key industry figures.

The project, which secured £6.5m of government funding from UKRI as part of the Transforming Foundation Industries Challenge, has officially launched and aims to demonstrate that concrete can be recycled to create a Slag Forming addition which could, when cooled rapidly, replace Portland cement.   

Portland clinker, one of the main ingredients in cement, is produced by firing limestone and other minerals in a kiln at extremely high temperatures (1,450 degrees Celsius), a process which accounts for more than 50% of the cement sector's emissions. 

By contrast, Cement 2 Zero will use recycled cement as the flux in the electric steel recycling process - powered by an electric arc furnace which uses renewable energy - the by-product of which, when cooled and ground, produces Portland cement clinker, which is then blended to make ‘zero-emissions’ cement.  

This innovative product known as Cambridge Electric Cement (CEC) could be made in a virtuous recycling loop, that not only eliminates the significant emissions of cement and steel production, but also saves raw materials.

The two-year industrial trial for producing the cement on an industrial scale will test each stage of the production process, bringing together the expertise of the Materials Processing Institute and the University of Cambridge researchers Dr Cyrille Dunant, Professor Julian Allwood and Dr Philippa Horton, who invented the process. 

Key supply chain partners on the project involved in the testing stage before the product is introduced in a live UK construction project also include Atkins, Balfour Beatty, CELSA, Day Aggregates and Tarmac.  

Chris McDonald, chief executive officer of the Materials Processing Institute, said: “Cement 2 Zero has the potential to make a significant contribution to achieving a zero-carbon society, secure and increase jobs in the UK cement and steel sectors and challenge conventional production processes, creating high-value materials from demolition waste.” 

Dr Dunant, who made the crucial discovery that the chemical composition of used cement is virtually identical to that of the lime-flux used in the conventional electric arc furnace steel recycling process, added: “We take the built environment around us for granted, new homes, schools, hospitals, workplaces, roads and railways, as well as infrastructure that provides us with clean water, sanitation and energy - all require cement which is an essential building material. 

“It’s estimated that annual production equates to more than 500kg of concrete per person on the planet per year, and it is not currently possible to produce the material without creating CO2 emissions. 

“This breakthrough offers a positive move in cement production and will support the industry response to the UK’s legally binding commitment to bring all greenhouse gas emissions to net zero by 2050."

The first phase of trial melts is being carried out by the Materials Processing Institute, initially in a 250kg induction furnace, before being scaled up to 6T. 

Once the process has been substantially trialled, developed and de-risked effectively, industrial scale melts will follow in CELSA’s electric arc furnace in Cardiff. 

Dr Philippa Horton, University of Cambridge, who created the project consortium, said: “If Cambridge Electric Cement lives up to the promise it has shown in early laboratory trials, when combined with other innovative technologies, it could be a pivotal point in the journey to a zero-emissions society. 

“The Cement 2 Zero project is an invaluable opportunity to collaborate across the entire construction supply chain, to expand CEC from the laboratory to its first commercial application.” 

Concrete is the most widely used material on earth after water, and it is fundamental to our way of life, our economy and shaping our world. 

However, the chemical and thermal combustion processes involved in the production of cement are a significant source of carbon dioxide (CO2) emissions – with more than four billion tonnes of cement produced each year, accounting for around seven per cent of global CO2 emissions, according to the Global Cement and Concrete Association (GCCA). 

Professor Julian Allwood, University of Cambridge and Cambridge Electric Cement, explained: “By combining steel and cement recycling in a single process powered by renewable electricity, we could supplement the global supply of the basic construction materials to support the infrastructure of a zero emissions world and to enable economic development where it is most needed.”