Concrete is perhaps the most significant material in shaping our modern world. Strong and durable, particularly when paired with steel, yet very affordable, concrete is the backbone of the world’s infrastructure.
However, cement and steel production are some of the highest contributors to global carbon emissions. Notably, cement accounts for 8% of global carbon emissions, while steel accounts for 11% according to some studies. Cutting these is then paramount, but there is a problem — concrete has been notorious for its poor recyclability.
A groundbreaking innovation from Cambridge University could change this narrative by simultaneously recycling old concrete and refining steel. It only requires waste from demolished buildings and steel-processing arc furnaces, meaning no new infrastructure is necessary. Moreover, this process doesn’t just reduce emissions — it has the potential to create zero-carbon cement when powered by renewable energy. Oh, and it recycles old concrete, thus minimizing waste. It’s like solving several problems at once.
Still, the way this works is perhaps the most captivating. Namely, Dr. Cyrille Dunant, the first author of the study, clarified that he already had an idea of removing water from cement with heat, then removing the sand and stones, and finally converting it back into clinker.
But what about the steel? Well, here is the genius part — the liquid metal would help the chemical reaction inside the arc furnace. Flux would still be necessary here to capture the impurities and protect the steel from oxidizing. However, instead of the usual lime flux, the researchers proposed using recycled cement paste, another plus for sustainability.
Another great advantage of this process is its scalability. For this month, the research team readies an industrial-grade trial that would produce 66 tons of cement in just two hours. Impressed? Wait until you hear that humanity could be making one billion tons of green recycled cement annually by 2050. That’s a quarter of the 4.1 billion tons of cement produced in 2022!
With that said, Professor Julian Allwood, who led the research, is coy on the idea of building our world more efficiently to catch CO2 targets sooner. “Producing zero emissions cement is an absolute miracle, but we’ve also got to reduce the amount of cement and concrete we use. Concrete is cheap, strong, and can be made almost anywhere, but we just use far too much of it. 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.”
