Hydration of calcium sulphoaluminate cements

A range of cements based on calcium sulphoaluminate, 4CaO·3Al₂O₃·SO₃. ‘C₄A₃S’ are commercially available. The phase contents of some commercial clinkers have been determined. Their hydration behaviour, including calorimetric heat evolutions, are reported. The clinker mineralogies control reactivity and dimensional stability; typically, sulphoaluminate formulations with added lime, gypsum and calcium aluminates are expansive, but those consisting of C₄A₃S and belite (Ca₂SiO₄) hydrate rapidly but give rise to dimensionally stable products. The role of accelerating and retarding admixtures is explored. The presence of admixes has a secondary role in controlling the dimensional stability of belite-sulphoaluminate formulations.