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c0lo [soylentnews.org] writes:

"Researchers from the University of Cambridge have developed a method to produce very low emission concrete at scale -- an innovation that could be transformative in the transition to net zero." reports ScienceDaily [sciencedaily.com]

The method, which the researchers say is "an absolute miracle," _{[are we taken as savages here?]} uses the electrically-powered arc furnaces used for steel recycling to simultaneously recycle cement, the carbon-hungry component of concrete.
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The Cambridge researchers found that used cement is an effective substitute for lime flux, which is used in steel recycling to remove impurities and normally ends up as a waste product known as slag. But by replacing lime with used cement, the end product is recycled cement that can be used to make new concrete.

The cement recycling method developed by the Cambridge researchers, reported in the journal Nature, does not add any significant costs to concrete or steel production and significantly reduces emissions from both concrete and steel, due to the reduced need for lime flux.
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Recent tests carried out by the Materials Processing Institute, a partner in the project, showed that recycled cement can be produced at scale in an electric arc furnace (EAF), the first time this has been achieved. Eventually, this method could produce zero emission cement, if the EAF was powered by renewable energy.
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"I had a vague idea from previous work that if it were possible to crush old concrete, taking out the sand and stones, heating the cement would remove the water, and then it would form clinker again," said first author Dr Cyrille Dunant, also from the Department of Engineering. "A bath of liquid metal would help this chemical reaction along, and an electric arc furnace, used to recycle steel, felt like a strong possibility. We had to try."
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"We found the combination of cement clinker and iron oxide is an excellent steelmaking slag because it foams and it flows well," said Dunant. "And if you get the balance right and cool the slag quickly enough, you end up with reactivated cement, without adding any cost to the steelmaking process."

The cement made through this recycling process contains higher levels of iron oxide than conventional cement, but the researchers say this has little effect on performance.

DOI:10.1038/s41586-024-07338-8 [nature.com] (free access)

4:33min vid [youtube.com]

Original Submission