The deterioration of cement composites containing nanosilica partially exposed to sulfate attack was studied, and the microstructure change of the composites was analysed by a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that nanosilica–cement composites had better sulfate resistance compared to plain cement composite under partial exposure to sulfate attack, and their sulfate resistance increased as the nanosilica content increased (in the range of 0 to 5 wt% replacing cement by weight). The main sulfate products were gypsum and ettringite within the surface and inner parts, respectively in both the immersed and evaporation portions of the nanosilica–cement composites, which was consistent with the plain cement composite. Thus, the incorporation of nanosilica did not change the distribution characteristics of the sulfate products within the composites partially exposed to sulfate attack. However, the addition of nanosilica reduced the amount of sulfate products in both the immersed and evaporation portions, and their amount decreased with the increase of nanosilica content. The evaporation portions of the composites suffered chemical sulfate attack rather than sulfate salt crystallization. Nanosilica–cement composites could be applied in real partial exposure environments containing sulfate ions.

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部分暴露于硫酸盐侵蚀的纳米二氧化硅-水泥复合材料的微观结构变化

研究了部分暴露于硫酸盐侵蚀的含纳米二氧化硅的水泥复合材料的劣化，并通过扫描电子显微镜（SEM）、能量色散谱（EDS）和 X 射线衍射（XRD）分析了复合材料的微观结构变化。结果表明，在部分暴露于硫酸盐侵蚀的情况下，纳米二氧化硅-水泥复合材料与普通水泥复合材料相比具有更好的耐硫酸盐性，并且随着纳米二氧化硅含量的增加（在 0 至 5 wt% 的范围内代替水泥的重量），它们的耐硫酸盐性增加。主要的硫酸盐产物是表面和内部的石膏和钙矾石，分别在纳米二氧化硅-水泥复合材料的浸渍和蒸发部分，这与普通水泥复合材料一致。因此，纳米二氧化硅的加入不会改变部分暴露于硫酸盐侵蚀的复合材料中硫酸盐产物的分布特征。然而，纳米二氧化硅的加入减少了浸渍和蒸发部分硫酸盐产物的数量，并且随着纳米二氧化硅含量的增加，它们的数量减少。复合材料的蒸发部分遭受化学硫酸盐侵蚀而不是硫酸盐结晶。纳米二氧化硅-水泥复合材料可应用于含有硫酸根离子的真实部分暴露环境。并且它们的量随着纳米二氧化硅含量的增加而减少。复合材料的蒸发部分遭受化学硫酸盐侵蚀而不是硫酸盐结晶。纳米二氧化硅-水泥复合材料可应用于含有硫酸根离子的真实部分暴露环境。并且它们的量随着纳米二氧化硅含量的增加而减少。复合材料的蒸发部分遭受化学硫酸盐侵蚀而不是硫酸盐结晶。纳米二氧化硅-水泥复合材料可应用于含有硫酸根离子的真实部分暴露环境。