Hydration mechanisms of hydratable alumina (HA) in citric acid at different pH are investigated in this study, aiming to improve rapid hydration process and massive hydration heat. By adding citric acid to adjust solution pHs to 2, 3, and 4, the crystal phase, morphologies, and microstructure of the HA hydrates are characterized by X-ray powder diffraction (XRD), differential scanning calorimetry (TG-DSC), and transmission electron microscopy (TEM), respectively. The results show that HA exhibits different hydration behaviors in different concentrations of acidic solutions. With decreasing pH of citric acid, the crystallinity of HA decreases whereas the dehydration process slows down. Excessive citric acid could displace hydroxyl which generates from pseudoboehmite gel. Meanwhile, the excess citrate ion can be absorbed on the surface of HA by forming numerous micelles, then compound to inhibit further hydration. Proper addition of citric acid helps to delay the hydration of HA and achieve better balance between bonding performance and hydration speed.

本文研究了柠檬酸中不同pH条件下可水化氧化铝（HA）的水合机理，旨在改善快速水合过程和大量水合热量。通过添加柠檬酸将溶液的pH值调节至2、3和4，HA水合物的晶相，形态和微观结构通过X射线粉末衍射（XRD），差示扫描量热法（TG-DSC）和透射电子显微镜（TEM）。结果表明，HA在不同浓度的酸性溶液中表现出不同的水合行为。随着柠檬酸pH值的降低，HA的结晶度降低，而脱水过程减慢。柠檬酸过多会取代假勃姆石凝胶产生的羟基。与此同时，多余的柠檬酸根离子可通过形成大量胶束而被吸收到HA表面，然后形成化合物以抑制进一步的水合作用。适当添加柠檬酸有助于延迟HA的水合，并在粘合性能和水合速度之间达到更好的平衡。