Research on the Hydration Properties of C₄A₃S-CSH₂ Cement System at Different Temperatures

Sulphoaluminate cement has the advantage of low-temperature application performance, but its hydration mechanism at low temperatures is not yet clear. Anhydrous calcium sulfoaluminate (C₄A₃S) is the main mineral in the composition of sulfoaluminate cement clinkers. In this paper, C₄A₃S mixed with gypsum (CaSO₄∙2H₂O) to form a C₄A₃S-CSH₂ cement system; X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and mercury intrusion analysis (MIP) to clarify the effect of temperatures on the hydration properties of C₄A₃S-CSH₂ cement system. The results showed that hydration of the C₄A₃S-CSH₂ cement system could carry on at low temperatures, even at -15 °C. The main hydration product was ettringite. Low temperatures did not change the types of the hydration products, but the low temperature of 0 °C was more favorable for the formation of ettringite. The early hydration of the C₄A₃S-CSH₂ cement system was inhibited by the decrease in temperature. However, hydration of the cement at 0 °C continued at a high rate after one day. Morphologies of the ettringite for the C₄A₃S-CSH₂ cement system at -15 °C were needle-like structures, while they were of columnar structure at 0 °C. The compressive strength of samples at 0 °C reached 82 MPa, which is significantly higher than that at 20 °C.