Hydration of Ca7ZrAl6O18 phase

Abstract The hydraulic properties of the Ca 7 ZrAl 6 O 18 (C 7 A 3 Z) phase as well as the hydration products and thermal decomposition mechanism of this hydrated phase were studied. Microcalorimetric analysis has shown that the C 7 A 3 Z phase reacts with water very quickly, especially in the first 2 h after the start of the experiment. Hydration of calcium zirconium aluminate proceeds with the formation of high refractory calcium zirconate (with melting point 2345 °C), apart from the hydrated, nearly amorphous material. According to the DTA–TG–EGA, FT-IR and SEM/EDS examinations it has been found that not only the hydrates CAH 10 , C 2 AH 8 and C 4 AH 19 are present, but also C 3 AH 6 (C = CaO, A = Al 2 O 3 , H = H 2 O), the only hydrated calcium aluminate which is a thermodynamically stable phase above 40 °C. Unhydrated Ca 7 ZrAl 6 O 18 and CaZrO 3 phases have been found by XRD, but crystalline hydrates have not been detected.