Setting and hardening properties of alite-barium calcium sulfoaluminate cement with SCMs

The effects of supplementary cementing materials (SCMs) on the performance of paste rheology, setting time, compressive strength and shrinkage of alite-barium calcium sulfoaluminate cement were investigated. The activation mechanism of SCMs in cement was also studied. Similar to Portland cement, the addition of SCMs was found to decrease the yield shear stress and viscosity of alite-barium calcium sulfoaluminate paste, prolong its setting time and lower the early compressive strength. It was also found to reduce the shrinkage of alite-barium calcium sulfoaluminate mortar. With an increase in the replacement ratio of slag for fly ash, the yield shear stress and plastic viscosity of paste with SCMs decreased in stages due to the ‘ball bearing' effect of fly ash and the initial and final setting times of paste with SCMs increased, with lime significantly restraining ettringite formation. Owing to hydraulic reactions at a later curing age and the close aggregate packing effect of SCMs, the mechanical properties of paste with SCMs increased significantly. Moreover, it was found that fly ash is activated more effectively than slag in alite-barium calcium sulfoaluminate cement at long-term curing ages, which is different from SCM activation in Portland cement.