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New machine can reclaim cement from recycled concrete

Yesterday, on World Environment Day, the Dutch companies New Horizon Urban Mining and Rutte Group presented a machine that can separate the ingredients of concrete, including cement. The reclaimed cement can in turn be reused in new concrete, saving a lot of CO2 emissions that would be generated in the production of new cement.

Concrete contains cement, the production of which releases a lot of CO2, as much as 6 per cent of the total global emissions. The cement forms a glue when mixed with water, binding together sand and gravel, the other ingredients of concrete. However, often, much more cement is used than is necessary, to speed up the hardening process. Because of this, a large amount of cement, between 30 and 50 per cent, has never been into contact with water and is therefore as good as new.

New Horizon uses urban mining, a process in which demolition waste is reclaimed and reused in new projects, to promote a circular economy. In their new project, they do this by reclaiming the unused cement in used concrete.

Their new machine grinds the concrete and separates three material streams: cement glue (cement that has been into contact with water), gravel, and a mixture of sand and unused cement. The latter, called Freement, can directly be reused in new concrete, saving a lot of CO2 emissions that would be generated in the production of new cement. The machine can recycle 130,000 tonnes annually.

The cement glue could theoretically be reused as well, by reheating it. However, the carbon and financial footprint is currently still too large to justify the process.

The technology of recycling concrete is not entirely new. Ten years ago, Koos Schenk came up with the idea, but his machine never came into production. Technology has progressed since then, but also the attitude toward reclaiming and reusing materials, even if current cement and concrete manufacturers still aren’t too pleased with the process.

Recycling concrete is not necessarily more expensive than making new. Project developers pay more for crushing and removing concrete than when New Horizon reclaims the material. In addition, in the future, when the costs for CO2 emissions in new building permits will increase, using reclaimed cement will become even cheaper. The second and third recycling machines have already been ordered.

Photos: Pexels / Pxhere