Water-to-cement ratio of calcium sulfoaluminate belite cements: Hydration, setting time, and strength development

Little published data is available to guide engineers in designing calcium sulfoaluminate belite (CSAB) cement mixtures with adequate workability, strength, and durability. This lack of understanding of design factors, especially the effect of varying w/c, represents a significant barrier to widespread CSAB use. In this study hydration, setting time, and strength development of two CSAB cements with w/c from 0.3 – 0.6 were evaluated. CSAB reaction kinetics varied with increased w/c depending on CSAB composition, specifically calcium sulfate content – with higher w/c increasing retardation in higher anhydrite/ye'elimite content cement, but reduced retardation in lower anhydrite/ye'elimite cement. For both cements, greater w/c led to greater total hydration, increased setting times, and reduced compressive strengths in the pastes and mortar samples. Setting time was linked more closely to anhydrite content than w/c, with greater sulfate volumes shortening setting times.