柠檬酸对建筑石膏缓凝作用影响因素的研究

Study on the Factors Influencing Retarding Effect of Citric Acid in Building Gypsum

研究了柠檬酸对建筑石膏凝结时间与流动度经时性的影响,以及建筑石膏细度、相组成、pH值、水化温度对柠檬酸缓凝性的影响。结果表明:柠檬酸是建筑石膏高效缓凝剂,可有效抑制其流动度经时损失;Ⅲ型无水石膏和二水石膏削弱柠檬酸的缓凝效果,比表面积增加,凝结时间缩短;柠檬酸在弱碱性条件下缓凝效果最好;柠檬酸的缓凝效果对温度很敏感,温度升高,缓凝性降低。

The influences of citric acid on the setting time and the time dependency of fluidity of building gypsum were investigated. Furthermore, the factors affecting the retarding property of citric acid were also studied such as gypsum particles fineness, phase composition, pH value and hydration temperature. The results indicate that citric acid is highly efficient retardant for building gypsum and it is able to inhibit the fluidity loss of fresh gypsum plaster with time effectively. The existence of Ⅲ -type anhydrate and dihydrate gypsum in phase composition would weaken the effect of citric acid. With the increase of specific surface area of gypsum particles, its setting time is shortened. In alkalescent liquid environment, the citric acid has the best retarding capability. In addition, the temperature also has a susceptive influence on its retarding effect which is decreased with the increase of temperature.