Experimental study of pure Class G cement hydration up to 150 °C and 50 MPa

A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.