Study on carbonation characteristics of cement spraying assisted by supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO 2 ) has the potential to enhance the pore structure and early strength of cement paste. In this study, the mechanical properties and carbonation behavior of cement paste treated with SC-CO 2 were systematically investigated by leveraging its high diffusivity. An innovative SC-CO 2 spraying technique was developed, and the effects of SC-CO 2 on the microstructure and carbonation fixation of cement paste were examined through comparative experiments. The results show that SC-CO 2 treatment can significantly accelerate the carbonation process. The carbonation depth is positively correlated with the water-cement ratio (the larger the water-cement ratio is, the deeper the carbonation depth is), and the thermogravimetric analysis (TG) and scanning electron microscope (SEM) further confirm that SC-CO 2 treatment effectively refines the microstructure of cement paste. Overall, SC-CO 2 spraying accelerates carbonation, fills pores, improves the pore structure, shortens the setting time, and enhances the early strength of cementitious material. This suggests that SC-CO 2 can be used to assist in spraying cement paste or thin spraying materials in the future construction process.