Strategies for carbon capture in concrete production

Cement compounds contain carbon-reactive metal oxides, reason why the Cement Technology Roadmap recommends the integration of carbon capture into the cement manufacturing process. The carbonation potential of cement is mainly due to calcium oxide (CaO), which represents around 60% of the cement composition. With this reasoning in mind, different strategies have been explored aiming at developing technologies for carbon capture by cement-based materials. Accelerated carbonation curing of cement-based materials is one of the approaches. However, despite some CO₂ capture effectiveness is reported, its industrial process is still a long way off. A second strategy consists of incorporating CO₂ during the mixing process, which has shown to speed up the hardening reactions of cement. However, this effect is of short-term and may negatively affect its long-term performance. The carbonation of cement waste is also a strategy for carbon capture, which maximizes the access of CO₂ to the calcium-rich compounds and enables the reuse of cement-based materials as filler addition. This chapter presents an overview of these three strategies, their pros and cons and main findings achieved, aiming at reducing the carbon footprint of concrete production, the most widely used building material on earth.