Cambridge engineers patent world’s first zero-emissions cement

Rose Mary Petrass


Three Cambridge engineers have filed a patent for their invention of what they claim is the world’s first ever zero-emissions cement.

Dr Cyrille Dunant, Dr Pippa Horton and Professor Julian Allwood, of the University of Cambridge, have been awarded £1.7 million ($A2.94 million) in research funding from The Engineering and Physical Sciences Research Council for what they call “Cambridge Electric Cement”, which is manufactured in a closed loop system from the demolition waste of old buildings. 

Cement production is the world’s biggest industrial cause of carbon pollution, responsible for 8 per cent of global emissions, according to Beyond Zero Emissions.

Replacing cement with a carbon-neutral alternative has been one of the biggest challenges faced by the built environment sector.

Until now, reduced-emissions cement has been made by mixing new reactive cement (clinker) with other supplementary materials. 

“If Cambridge Electric Cement lives up to the promise it has shown in early laboratory trials, it could be a turning point in the journey to a safe future climate,” Professor Allwood said in a statement.

“Combining steel and cement recycling in a single process powered by renewable electricity, this could secure the supply of the basic materials of construction to support the infrastructure of a zero emissions world and to enable economic development where it is most needed.”

Professor Julian Allwood / Cambridge University Engineering Department
Professor Julian Allwood / Cambridge University Engineering Department

How it’s made

The new zero-emissions cement is produced by crushing concrete waste to separate stones and sand from the mixture of cement powder and water that binds concrete together. 

The old cement powder is then used instead of lime-flux in steel recycling. According to Mr Dunant, the chemistry of used cement is virtually identical to that of the lime-flux used in conventional steel recycling processes. 

This ensuing process is complicated, but basically involves melting steel, which creates a by-product material called “slag”.

Molten slag carried outside and poured into a dump. Wikimedia commons / Javier Rubilar / Caletones

After the recycled steel is removed, the liquid “slag” cools rapidly in the air, and is then ground up to form a powder. This process creates a powder chemically identical to clinker which in conventional “Portland” cement, which releases the majority of CO2 process emissions. 

In pilot trials, the researchers have found that this process creates cement that is virtually identical to today’s conventional process.

Cement Process Comparison. UK FIRES / The University of Cambridge

The research is part of a large multi-university UK FIRES programme, led by Professor Allwood, that aims to aid in the rapid transition to zero emissions based on today’s technologies.