关键词: &beta, -半水石膏, 冶金废渣, 凝结, 动力学, 结晶

Abstract: As one of the most versatile building materials, gypsum possesses sound and thermal insulation and fireproof characteristics. However, gypsum plaster sets quickly, which limits its application. It is discovered that the waste slags have certain retarding effect on β-semi-hydrated gypsum, while quartz sand has roughly no influence on the setting time of gypsum. When mixed with 5% of finely ground manganese slag or steel slag, the initial setting time of gypsum plaster reached 100 min. The hydration process of β-semi-hydrated gypsum was studied in order to reveal the underlying reasons. The results showed that the incorporation of waste metallurgical slag reduced the formation rate of di-hydrate gypsum and blocked the hydration of gypsum. The retarding mechanism of steel slag for β-semi-hydrated gypsum was different from other retarders. It not only changed the shape of di-hydrate gypsum crystals, but also effectively inhibited the hydration of semi-hydrated gypsum. The micro structure of gypsum plaster was observed by SEM. It was found that, at the same curing time, di-hydrate gypsum crystals were short in the system containing steel slag or manganese slag, and the quantity of gypsum decreased as compared with the blank, which is in good consistence with the XRD analysis. It is the main cause for retarding effect and resulting strength loss of the gypsum system. When steel slag was used to regulate the setting time of building gypsum, the lower content of di-hydrate and certain acidity were favorable to the regulation of the setting time. Compared to commonly used retarders, as sodium citrate and sodium polyphosphate, ground slag and manganese slag have excellent retarding effect and the advantages of low cost and low strength loss.

Key words: β-semi-hydrated gypsum, waste metallurgical slag, setting, kinetics, crystallization