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Scientists make breakthrough in recycling old concrete — and it could have major implications

"We could dramatically reduce the amount of concrete we use without any reduction in safety."

"We could dramatically reduce the amount of concrete we use without any reduction in safety."

Photo Credit: Cambridge Electric Cement

Cambridge researchers may have a new adage thanks to an ingenious method that can apparently make cleaner cement as part of the steelmaking process. 

As a result, it seems that two dirty materials can make a clean one. 

While the would-be proverb isn't quite on par with offerings from Confucious, the science behind the breakthrough could revolutionize manufacturing in the building sector. It's widely reported that the cement and steelmaking industries make up about 8% and 7% of annual global air pollution. 

"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," study first author Cyrille Dunant said in a New Atlas story. "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."

The result is Cambridge Electric Cement. It all starts by gathering concrete from demolition sites. After being crushed, the separated cement is used in place of lime-flux needed in steel recycling, making the process cleaner. 

After the recycled steel is gathered, the hot mix is quickly cooled and ground up. What's left works perfectly for the base material to make new cement. Testing showed the recycled mix to perform on par with original concrete, having the same chemical composition, per the researchers and New Atlas.

"Miraculously it turns into new Portland cement," research lead Professor Julian Allwood said in a video clip

A diagram of the process highlights the truly circular nature of the innovative technique, from demo to construction. 

"As well as being a breakthrough for the construction industry, we hope that Cambridge Electric Cement will also be a flag to help the government recognize that the opportunities for innovation on our journey to zero emissions extend far beyond the energy sector," Allwood told New Atlas. 

The story notes that the process doesn't add to production costs and greatly reduces air pollution. If renewables power the electric arc furnace, the effort is even more planet-friendly. 

There are numerous cleaner cement inventions in development. CarbonCure's method injects planet-warming carbon dioxide into concrete, safely storing it. The right breakthrough could help revolutionize how we build our infrastructure and use energy. Reducing air pollution from production of the world's most commonly used building materials can improve air quality, among other benefits. NASA has linked planet warming to the likelihood of more severe weather events, for example. 

At Cambridge, the researchers are putting their method through trial runs. They told New Atlas that it's possible the technique could produce 1.1 billion tons of electric cement by 2050, if it's scaled. 

"Concrete is cheap, strong, and can be made almost anywhere, but we just use far too much of it," Allwood said in the story. "We could dramatically reduce the amount of concrete we use without any reduction in safety, but there needs to be political will to make that happen."

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