Enhancing In Situ Carbonation of Fresh Paste via Cal-Al Layered Double Oxide and Mixing Parameter Optimization

CO₂ mixing is one of the implementation techniques of carbon capture utilization and storage (CCUS) in concrete to tailor the performance of cementitious materials and reduce the carbon footprint. Therefore, increasing the total amount of carbon capture capacity of cement-based materials has become the key point of recent research. This study investigates the influence of Cal-Al layered double oxide (LDO) and mixing parameters on key properties of cement pastes under CO₂ mixing, including mechanical performance, microstructure, phase assemblages, and carbon capture capacity. A particular emphasis was placed on evaluating a novel bubble mixing technique, which was developed to enhance the conventional atmospheric mixing process. The results indicate that, compared to the traditional method, bubble mixing reduced the mixing intensity by 10% but increased the effective carbon sequestration capacity by 0.68%. The observed strength reduction after bubble mixing was consistent with higher water adsorption, indicating the formation of a more porous structure. A higher carbon capture efficiency was achieved with bubble mixing compared to atmospheric mixing, as revealed by further investigation. Crucially, the introduction of LDO significantly enhanced the carbon capture capacity, with improvements of up to 34% compared to the groups without LDO. This highlights the substantial potential of LDO in reducing the carbon footprint of cementitious materials and offers a novel insight for enhancing CO₂ mixing in cement.