Synthesis and hydration of calcium sulfoaluminate-belite cements with varied phase compositions

The production of portland cement is energy intensive and contributes significantly to greenhouse gas emissions. One method of reducing the environmental impact of concrete production is the use of an alternative binder, such as calcium sulfoaluminate-belite (CSAB) cement. The relatively low lime requirement of CSAB cement compared to portland cement reduces energy consumption and carbon dioxide emissions from cement production. Moreover, CSAB cement can be produced at temperatures approximately 200 °C lower than portland cement, further reducing energy and carbon dioxide. Major drawbacks to the implementation of CSAB cements are the lack of standard phase composition and published data on composition-processing-performance relationships. In this study, three CSAB cement clinkers with different phase compositions were synthesized from reagent-grade chemicals. The synthetic clinkers were analyzed for phase composition using X-ray diffraction and phase distribution using scanning electron microscopy. The synthetic clinkers were then tested for hydration rate using isothermal conduction calorimetry to investigate the effects of phase composition and gypsum addition on early-age hydration behavior. A proportioning method for predicting phase composition was refined and an equation for calculating the minimum gypsum content for CSAB cement clinker was developed.