Properties and hydration characteristics of cementitious blends with two kinds of solid waste-based sulfoaluminate cement

Abstract

Blends of high belite sulfoaluminate cement (HBSAC) and iron-rich sulfoaluminate cement (IRSAC) can leverage the advantages of both materials and adapt to different application requirements (e.g., hydration heat adjustment, mechanical strength enhancement, dimensional stability maintenance etc.). In this study, the physicochemical properties and hydration characteristics of solid waste-based HBSAC and IRSAC blends with different blending ratios (100–0, 75–25, 50–50, 25–75, and 0–100) were investigated. Attributed to the higher amount of AFt produced by the hydration of active C4A3-xFxS̅, the compressive and early flexural strengths of the blends increase with increasing IRSAC proportion, and there shows a high correlation between the compressive strengths and the AFt content. However, the late-stage flexural strength increases with the rising proportion of IRSAC before it reaches to 50%, and afterwards, the flexural strength shows a declining trend, which is closely related to the change in porosity. The needle-like AFt formed by HBSAC and rod-like AFt formed by IRSAC in the blends contribute to a crystal spatial interlock, resulting in the formation of a denser microstructure. Thus, the blend is more favourable for the development of late-stage flexural strength than the single microstructural form of AFt in HBSAC or IRSAC. This study holds significant guiding implications for directing the rational blending of HBSAC and IRSAC, thereby enhancing the performance of the cement.