MainConcrete is the most used material on the planet, after water, and is responsible for approximately 7.5% of total anthropogenic CO2 emissions1,2,3.The two main strategies deployed to date to reduce emissions from Portland cement production are fuel switching (using fossil gas, municipal waste or biofuels instead of coke and petcoke) and increased use of substitution materials, such as fly ash and slag. However, these strategies cannot lead to zero emissions. Moreover, the two most common sub...