Improvement of calcium sulfoaluminate foamed concrete by carbon dioxide foam: hydration activation and pore structure optimization

Abstract

This study leverages the low-alkali, early-strength, and rapid-setting properties of CSA to develop a foamed concrete utilizing CO₂ foam. The results indicate that in comparison to CSA prepared using air foam, the 1 d compressive strength of the formulation with CO₂ foam shows an increase of 31 %. Furthermore, when compared to OPC produced with air foam, this strength enhancement reaches up to 74 %. Notably, strength development predominantly occurs within 7 d. This enhanced early strength can be attributed to the role of CO₂ in promoting hydration reactions of calcium sulfoaluminate, which facilitates nearly complete hydration and substantially elevates ettringite content. However, excessive amounts of CO₂ may lead to over-consumption of ettringite, which could adversely affect the rate at which strength develops. The incorporation of CO₂ foam significantly reduces the connectivity and permeability coefficient within the foamed concrete, thereby lowering both thermal conductivity and water absorption rates.