The mineralogy of the CaO–Al2O3–SiO2–H2O (CASH) hydroceramic system from 200 to 350 °C

We describe a quantitative mineralogical study of the hydrothermal reactions of an oil well cement with added silica and alumina, hydrated at temperatures from 200 to 350 °C. We compare the products with pure end member systems and find phase stability can be altered radically, even by small amounts of additive. The upper temperature limits of α-C2SH (< 250 °C), and 1.1 nm tobermorite C5S6H5 (< 300 °C) are increased. C8S5, reported in a cement-based system for the first time, is stable to 300 °C and is believed to prevent foshagite C4S3H formation below 350 °C. Hydrogarnet C3AS3−yH2y is the only aluminum bearing phase at < 300 °C but it coexists with C4A3H3 and bicchulite C8A4Si4H4 at higher temperatures. The presence of alumina increases the stability of 1.1 nm tobermorite greatly and also to a lesser degree of gyrolite.