The world’s first zero-emissions cement has been invented by three engineers in Cambridge
Three Cambridge engineers, Dr Cyrille Dunant, Dr Pippa Horton and Professor Julian Allwood, have filed a patent and been awarded new research funding for their invention.
Replacing cement is one of the hardest challenges on the zero-emissions roadmap. Reduced-emissions cement has been achievable – by mixing new reactive cement (clinker) with other supplementary materials – but it has not been possible to make the reactive component of cement without emissions.
The new cement is made in a virtuous recycling loop that eliminates the emissions of cement production, saves raw materials, and reduces the emissions needed to make lime-flux.
The inspiration for Cambridge Electric Cement struck inventor Dr Dunant when he noticed that the chemistry of used cement is virtually identical to that of the lime-flux used in conventional steel recycling processes. The new process begins with concrete waste from the demolition of old buildings. This is crushed, to separate the concrete (stones and sand) from the mixture that binds them (cement powder and water). The old cement powder is then used instead of lime-flux in steel recycling. As the steel melts, the flux forms a slag that floats on the liquid steel, to protect it from oxygen in the air. After the recycled steel is tapped off, the liquid slag is cooled rapidly in air, and ground up into a powder which is virtually identical to the clinker which is the basis of the new cement.