Nanoparticle stabilized carbon dioxide foam: Improving hydration, carbonation and pore structure of foamed concrete

This study employed nano-silica (NS) and nano-calcium carbonate (NC) to stabilize CO₂ foam, which was subsequently employed in the production of CO₂ foamed concrete (CFC). The impacts of varying dosages of NS and NC on the characteristics of CO₂ foam and the properties and microstructure of CFC were investigated. The incorporation of NS and NC significantly enhanced the stability of CO₂ foam, with optimal foam stability achieved at content of 1 % for NS and 1.5 % for NC, respectively. The fluidity of fresh CFC paste exhibited a gradual decline as the content of nanoparticles increases. In addition, when the foam was optimal stable, the strength of CFC can be increased by 36 % and CO₂ uptake by 1.8 % on average. NS owing to its crystal nucleus effect and volcanic ash effect, concurrently facilitated both hydration and carbonation processes. This dual action effectively filled the defects present on the pore walls and enhanced the strength. Whereas NC acted as a nucleation site effect for calcium carbonate formation, further advancing the carbonation process and reinforcing the strength of the pore walls. Above effects to varying degrees significantly reduced the pore throat radius, length and the number of interconnected pores of CFC, and optimized the pore size distribution, uniformity and sphericity, thereby reducing the water absorption rate of CFC and enhancing its mechanical properties.