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

摘要： 石膏制品具有优良的隔声、隔热、可呼吸和防火性能，是公认的环保型建筑材料。但是β-半水石膏凝结时间短，应用受到限制。本文利用冶金废渣对β-半水石膏进行改性，发现冶金废渣对石膏具有一定的缓凝作用。掺入5%（以半水石膏为基础）磨细的钢渣或锰渣时，石膏浆体的初凝时间可达100min以上，而对照组的磨细石英砂对石膏的凝结时间几乎没有影响。为揭示其原因，对半水石膏水化过程进行了分析研究。结果表明，几种冶金废渣降低了二水石膏的生成速率，阻滞了β-半水石膏的水化进程。钢渣对β-半水石膏的缓凝机理与其他缓凝剂有所不同，不仅改变了二水石膏晶体形状，而且有效抑制了半水石膏的水化反应。利用SEM观察石膏硬化体的微观结构，在相同的养护时间下含有钢渣和锰渣的体系中二水石膏晶体变短，与空白样相比数量也有所减少，这一点与XRD分析结果相互印证，是造成石膏体系凝结时间延长和强度损失的主要原因。研究发现，钢渣直接用于调控β-半水石膏的凝结时间时，较低的二水相和一定的酸性对钢渣调节石膏凝结时间有利。与柠檬酸钠、多聚磷酸钠等常用石膏缓凝剂相比，磨细钢渣、锰渣对石膏强度影响较小，成本优势明显。

关键词: &beta, -半水石膏, 冶金废渣, 凝结, 动力学, 结晶