Chemical equilibria between C-S-H and ettringite, at 20 and 85 °C

Mixes of C–S–H and ettringite were synthesized in suspension systems and their equilibria were studied at 20 and 85 °C. Concentrations in solution (calcium, sulfate, aluminium) were measured and the mineralogical state of the systems was studied by means of X-ray diffraction. The equilibria between C–S–H and ettringite are described. The relative importance of sulfate bound to the C–S–H is evaluated. The kinetics of ettringite reprecipitation from a “C–S–H–ettringite” system at 85 °C placed at 20 °C are also evaluated.