Storing CO₂ while strengthening concrete by carbonating its cement in suspension

Cement is a key constituent of concrete and offers a large sequestration potential of carbon dioxide (CO₂). However, current concrete carbonation approaches are hindered by low CO₂ capture efficiency and high energy consumption, often resulting in weakened concrete. Here, we conceptually develop and experimentally explore a carbonation approach that resorts to injecting CO₂ into a cement suspension subsequently used to manufacture concrete, turning the carbonation reaction into an aqueous ionic reaction with a very fast kinetics compared to traditional diffusion-controlled approaches. This approach achieves a CO₂ sequestration efficiency of up to 45% and maintains an uncompromised concrete strength. The study shows that the CO₂ injection rate influences the polymorph selectivity of mineralized calcium carbonate (CaCO₃) depending on the local environmental conditions and impacts the strength of concrete. The technological simplicity of the proposed approach enables a reduced carbon footprint and promising prospects for industrial implementation.