Potential utilization of CO2 foams in developing lightweight building materials

Energy conservation and emission reduction are key focuses in the field of building engineering. In this study, carbon dioxide gas was utilized to develop carbon dioxide foam cement paste materials. The properties of the samples were evaluated by considering the optimal foaming agent, water-cement ratio, foam-grout ratio, and pump speed. To elucidate the carbonation mechanisms, the microstructure and phase composition were analyzed with X-ray diffraction and scanning electron microscopy, respectively. The results demonstrated that the 3-day compressive strength of the test sample was 272.72% higher than that of an air foam cement paste. Additionally, the carbon dioxide foam cement paste exhibited a lower density than ordinary cementbased paste, while its 3-day compressive strength was 14.08% higher than that of the ordinary cement-based paste. Moreover, the price per cubic meter of the carbon dioxide foam cement paste was 19.02% lower than that of the ordinary cement-based paste. The introduction of carbon dioxide foam led to the consumption of hydration products near the voids and accelerated the carbonation reactions of the cement particles around the void-cement interfaces. This promoted the solidification of the foam within the cement paste, ultimately enhancing the early strength of concretion.