Cambridge Engineers Crack Cement Conundrum

Cambridge Engineers file patent to world’s first zero emissions cement

Concrete is the most widely used building material in the world.  It is strong, durable and versatile.  Cement is a key ingredient that makes up concrete, along with water, sand and gravel, and acts as the binding material, hardening with water and tying together all the aggregate materials.

Cement production, however, generates around 2.5 billion tonnes of carbon dioxide (CO2) per year – around 8% of the global total.  After water, this makes it the second most widely used substance on Earth, and if it were a country, the third largest CO2 emitter in the world, behind only China and the US.

There are many options to make cement with reduced emissions.  These are most commonly based on mixing a substance called clinker (new reactive cement) with other supplementary materials.  It has not been possible, until now however, to make this reactive component without CO2 emissions.

Cambridge engineers Dr Cyrille Dunant, Dr Pippa Horton and Professor Julian Allwood recently filed a patent application to the world’s first emissions-free method of producing cement.

Dunant realised that the chemistry of used cement was almost identical to that of lime-flux, which is used in steel recycling processes.  The new process starts with concrete waste from, for example, the demolition of old buildings.  This waste is crushed so as to separate the stones and sand that form concrete from the mixture of cement powder and water that binds them together.

This old cement powder is then used instead of lime-flux in steel recycling.

As the steel melts, a slag is formed that floats on the liquid steel.  The recycled steel is tapped off and the liquid slag is cooled rapidly in air and ground up into a powder that is virtually identical to clinker.

Professor Julian Allwood has said that

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

The invention of the new cement by the Cambridge team has led to them being rewarded a research grant of £1.7m.  This will enable Dunant, Horton and Allwood to fund an additional team of researchers to probe the range of concrete wastes that this process can be applied to, and confirm the performance of the resulting material.

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