Effect of pore water saturation on the supercritical carbonation of cementitious materials

The optimization of pore water saturation is essential to improve the supercritical carbonation efficiency of cementitious materials. In this study, a control method was developed to adjust the pore water saturation of cementitious materials to predetermined target values, thereby achieving a uniform distribution of pore water within the specimens. Based on this approach, a systematic supercritical carbonation test was conducted, the effects of pore water saturation and water-cement ratio on carbonation efficiency was researched by measuring carbonation depth, which reaches its maximum at a pore water saturation of 0.50. The effect of pore water saturation on the supercritical carbonation depth was clarified. Additionally, a novel method was proposed to determine the Ca(OH)₂ and C–S–H contents of cementitious materials before carbonation using inverse derivation from the differences in thermogravimetric analysis (TGA) results. Furthermore, microscopic techniques, including scanning electron microscopy (SEM), were employed to investigate the mechanisms of supercritical carbonation in cementitious materials under different pore water saturation levels. The influence of pore water saturation on the carbonation process was thereby elucidated.