This study examined the influence of the crystallinity of added nano-alumina on the sulfate resistance of ordinary Portland cement (OPC) paste. Two crystalline types of nano-aluminas (α-and γ-phase) were incorporated in cement pastes, which were exposed to sulfate solution. In the results, both paste samples having α- and γ-phase aluminas had accelerated compressive strength loss and increased length expansion compared to the sample without alumina addition. In particular, the rapidly decreased dynamic elastic modulus of the nano-alumina added samples postulates the greatly increased internal stress likely by the increased formation of volume expansive reaction products, such as ettringite, which was supported by the XRD and TG results. The greater ettringite formation in the nano-alumina added samples was likely due to reactive AH₃ (=Al(OH)₃) gel formation as the higher consumption degree of portlandite in the alumina added samples indirectly indicates the active AH₃ gel formation, resulting in additional ettringite formation from the reaction of AH₃ with Na₂SO₄ solution. A further degree of sulfate attack was observed in the γ-alumina added sample for the long-term Na₂SO₄ exposure (180 days) mainly due to the greater degree of gypsum formation inducing more internal expansive stress compared to the α-alumina added sample.

本研究考察了添加纳米氧化铝的结晶度对普通硅酸盐水泥 (OPC) 浆体抗硫酸盐性的影响。将两种结晶类型的纳米氧化铝（α 相和 γ 相）掺入暴露于硫酸盐溶液的水泥浆中。在结果中，与未添加氧化铝的样品相比，具有 α 相和 γ 相氧化铝的两种浆料样品都加速了抗压强度损失并增加了长度膨胀。特别是，添加纳米氧化铝的样品的动态弹性模量迅速下降表明内部应力大大增加，这可能是由于体积膨胀反应产物（例如钙矾石）的形成增加，这得到了 XRD 和 TG 结果的支持。添加纳米氧化铝的样品中更多的钙矾石形成可能是由于反应性 AH₃ (=Al(OH) ₃ ) 凝胶形成，因为氧化铝添加的样品中钙钙石的较高消耗程度间接表明活性AH ₃凝胶形成，导致AH ₃与Na ₂ SO ₄溶液反应额外的钙矾石形成。在长期暴露于 Na ₂ SO ₄中（180 天），在添加 γ 氧化铝的样品中观察到更大程度的硫酸盐侵蚀，这主要是由于与添加的 α 氧化铝相比，更大程度的石膏形成导致更大的内部膨胀应力样本。