HIGHLY REACTIVE BETA-DICALCIUM SILICATE .5. INFLUENCE OF SPECIFIC SURFACE-AREA ON HYDRATION

The hydration of beta-C2S prepared from hillebrandite [Ca2(SiO3)(OH)2] and having specific surface areas of 6.8, 5.5, and 3.1 m2/g was inves tigated. Different specific areas were obtained by varying the dissoci ation temperature of hillebrandite. In addition, the hydration of beta -C2S synthesized from high-temperature solid-state reaction was also s tudied as a comparison. The specific surface area exerts a strong infl uence on the hydration rate, which increases as the surface area incre ases. The degree of influence changes with the reaction, becoming grea ter as hydration progresses. There is initially a linear relationship between specific area and the time required to complete a specific rea ction. The specific surface area also affects the reaction mechanism. In the case of specific areas of 5.5 m2/g or less, the reaction change s from a chemical reaction to a diffusion-controlled one, and the degr ee of reaction comes almost to a halt at 80% to 85%. The Ca/Si ratios of hydrate and the silicate anion structures were also investigated in this study.