The mechanisms of external sulfate attack on cement mortars containing nano silica have been studied under full immersion conditions after 3 years. The sulfate degradation processes were compared between sodium sulfate and magnesium sulfate solutions with nano-silica replacements of 0, 1, and 8 wt% in CEM I Portland cement. Expansion, mass/strength loss, and microstructural alterations (spatial distribution of secondary phases and chemical compositions on C–S–H) of the degraded mortar were experimentally studied. The solution information was estimated from thermodynamic modeling, which was further used to predict the phase assemblage and the formation and expansion pressure of ettringite. The results showed that the degradation mechanisms were completely contradicted between the exposure solutions: the addition of nano silica increased the sulfate resistance in sodium sulfate solutions, the predicted low crystallization pressure resulted in low expansion, whereas the reduced sulfate resistance in magnesium sulfate solutions occurred where decalcification played a major role.

研究了3年后在完全浸泡条件下外部硫酸盐对含有纳米二氧化硅的水泥砂浆的侵蚀机理。比较了 CEMI 波特兰水泥中硫酸钠和硫酸镁溶液的硫酸盐降解过程，其中纳米二氧化硅的替代量为 0、1 和 8 wt%。对降解砂浆的膨胀、质量/强度损失和微观结构变化（第二相的空间分布和 C-S-H 上的化学成分）进行了实验研究。通过热力学模型估计溶液信息，进一步用于预测钙矾石的相组合以及形成和膨胀压力。结果表明，暴露溶液之间的降解机制完全矛盾：纳米二氧化硅的添加增加了硫酸钠溶液中的硫酸盐抗性，预计的低结晶压力导致低膨胀，而硫酸镁溶液中的硫酸盐抗性降低发生在以下位置：脱钙发挥了重要作用。