Kinetics of hydrothermal reactions have been studied for mixtures of CaO and quartz (<10 μm 10-20 μm) with Ca/Si = 0.8 and 1.0 in stirred suspensions at 120 - 180°C. Reaction proceeds through the sequence: Ca(OH)2 + SiO2 → Ca-rich C-S-H + SiO2 (at 120°C) → poorly crystalline tobermorite (at 140°C)→ highly crystalline tobermorite (at 180°C) → xonotlite at 180°C and Ca/Si = 1.0 and 180°C and Ca/Si = 0.8 if 10-20 μm quartz is used. Reaction is controlled by dissolution of the quartz. For both Ca/Si ratios the radius of the 10-20 μm quartz decreases at a constant rate, viz 0.85 μm/h at 180°C, 0.13 μm/h at 140°C, 0.04 μm/h at 120°C. © 1977.
