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Chemical Engineering

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A new way to capture CO2 in cement

| By Mary Page Bailey

Technologies designed to capture and store CO2 emissions from industrial operations are rapidly gaining traction, but finding ways to economically utilize the captured CO2 has posed challenges. A team of engineers from the University of California Los Angeles’ (UCLA; Institute for Carbon Management have developed a new cement formulation, into which captured CO2 emissions are directly infused.

Traditional cement is based on calcium silicate, but the new CO2-infused cement, branded under the name CarbonBuilt, uses hydrated lime, which is known to quickly absorb CO2. The team developed a new method, wherein as CarbonBuilt concrete hardens and strengthens, captured CO2 is quickly absorbed and permanently trapped. When compared to traditional concrete, the CarbonBuilt formulation reportedly reduces concrete’s carbon footprint by more than 50%, all while demonstrating comparable strength and durability. Contributing to this footprint reduction is CarbonBuilt’s Reversa process, which promotes the re-use of waste streams like flyash while significantly reducing the amount of cement binder needed to produce concrete. Furthermore, the process does not require operation at extreme temperature or pressure. Another benefit of capturing CO2 in cement is that, unlike other CO2 -mitigation methods, gas captured from industrial fluegas can be directly utilized without additional purification or conversion steps.

Last year, the team began an industrial-scale demonstration of its process in Wyoming that produced around 150 metric tons of CarbonBuilt concrete. A second demonstration was recently completed at the National Carbon Capture Center in Alabama, producing more than 5,000 concrete blocks using CO2 emissions from coal and natural-gas power plants. Each block can store around 0.75 lb of CO2. The team expects to significantly scale up production capacities in the coming years.