养护条件对硅钙渣基碱激发胶凝材料性能、反应产物及微观结构的影响

Effects of Curing Condition on Properties,Reaction Products and Microstructure of Calcium Silicate Slag-based Alkali-activated Cementitious Materials

采用X射线衍射、红外光谱、热重-差示扫描量热分析、压汞法及扫描电子显微镜等手段,分别对恒温潮湿空气(MA)、自然密封空气(SA)、高温潮湿空气(HA)3种养护条件下,硅钙渣基碱激发胶凝材料的性能及反应产物、微观结构进行研究。结果表明:在3种养护条件下,虽然主要产物均为水化硅铝酸钙凝胶,但试样的致密程度及强度性能不同,其中经HA养护试样的致密程度及强度最高。与MA相比,在HA养护条件下,由于温度提高对碱激发反应的促进作用,产物数量增加,试样的致密程度及强度性能显著提高;在SA养护条件下,虽然温度提高对碱激发反应的促进作用会导致产物数量增加,使试样中毛细孔分布向低孔径方向移动,但由于试样内部相对湿度降低的阻碍作用,因此SA养护对试样致密程度及强度性能的提高作用微弱。

The calcium silicate slag-based alkali-activated cementitious materials were synthesized and cured in moist air （MA）, sealed air （SA）, steam air （HA）, respectively. The mechanical properties, reaction products and microstructure were investigated by X-ray diffraction, infrared spectroscopy, thermogravimetry analysis-differential scanning calorimetry, mercury intrusion porosimetry and scanning electron microscopy. The results show that the main reaction products under three curing conditions are calcium alumina silicate hydrate gels. The density and mechanical properties vary with curing conditions. The specimens cured in HA exhibitthe densest microstructure and optimum mechanical properties. As compared to MA, the content of reaction products in specimens cured in HA increases due to the promotion of elevated temperature, giving rise to the optimization of density and mechanical properties. When cured in SA, despite the fact that a higher temperature contributes to the alkali-activation, as well as the distribution shift of capillary pores to lower diameters, the decrease of inner relative humidity of specimens prevents the alkali-activation. As a result, it is difficult to increase the density and mechanical properties of specimens cured in SA.