Abstract
An expansive additive containing lime(CaO), ye’elimite(3CaO・3Al2O3・CaSO4) and Anhydrite(CaSO4) was treated with high-temperature carbonation, and the effects of the treatment temperature and time on weathering resistance of the treated expansive additive were examined. After carbonation treatment between 400℃ and 800℃, the weathering was suppressed. Among the compounds constituting the expansive additive, the lime actively reacted with CO2 under high-temperature environment, the film of calcium carbonate was formed on the surface of the free lime. While the ye’elimite and anhydrite showed slow reaction with CO2. The hydration activity of calcium carbonate is smaller than that of lime, the reaction between the moisture and the expansive additive was suppressed, which seemed to have contributed to weathering resistance. From the viewpoints of expansion performance and improvement of weathering resistance, it can be considered preferable to apply carbonation treatment to the expansive additives between 500℃ and 600℃ for a short time.
