Preparation and properties of carbon dioxide foamed concrete using nanoparticles as foam stabilizer and pre–carbonated cement slurry

Abstract

The stability of carbon dioxide (CO2) foam is critical for preparation and performance of CO2 foamed concrete (CFC). This study evaluated the effectiveness of nanoparticles for stabilizing CO2 foam and pre–carbonation of cement slurry for mitigating CO2 foam loss during CFC preparation, and conducted a comparative study of CO2 foam, pre-carbonized slurry and CFC, aiming at preparing CFC with excellent performance. The results demonstrated that the incorporation of nano–silica can significantly enhance the stability of CO2 foam, with an improved half–life and diameter distribution. The pre–carbonation process optimized consistency and alkalinity of cement slurry and increased the retention rate of CO2 foam after its introduction into cement slurry, thereby facilitating the production of low–density CFC. CFC exhibits high compressive strength and early internal temperature, and has a low water absorption. The presence of CO2 within pores and their subsequent formation of potential negative pressure via carbonation reaction contributed to a much lower thermal conductivity of CFC compared to air foamed concrete. Moreover, a thin layer of calcium carbonate was formed on the inner wall, which can densify the microstructure and modify the pores. Although the carbonation degree of CFC may be lower compared to that of conventional carbonation–cured foamed concrete, the internal and uniform carbonation within CFC greatly enhanced material strength. The non–destructive nuclear magnetic resonance results show that CFC has a more concentrated pore size distribution with fewer fine pores and a smaller pore throat radius.