Carbon sequestration in cementitious systems through CO2-rich hydration and chemically enforced CO2 mineralization

Cementitious materials as a medium of carbon capture, and utilization (CCU) have recently attracted considerable attentions. Atmospheric CO2 can be absorbed in hardened concrete, which can be also accelerated by early age CO2 curing. Compared to the CO2 curing of concrete materials, in-situ CO2 mixing technology can be widely applied because it can be used in a batch plant without an additional curing facility. In this study, the CO2 mixing time was set as the primary variable to elucidate the precipitation of the carbonate phases in the early stages and its effect on cement hydration. The dissociated CO2 is directly mineralized into calcium carbonate (CaCO3) in calcite phase. In addition, the longer the CO2 mixing time, the greater the precipitation of calcite (i.e., CCU capacity), thereby densifying the internal microstructure and improving early strength development. Interestingly, a certain amount of calcite converted to monocarboaluminate—an important factor for quantitatively assessing the degree of mineral carbonation in cementitious materials.