中文摘要：

采用X射线衍射和扫描电镜，观测不同活性的氧化镁膨胀剂在不同水化龄期的产物，结合胶砂试件的限制膨胀率和强度测定结果，探究了不同活性的氧化镁膨胀剂的水化过程、膨胀特性和机理。结果表明：氧化镁的活性高，会减小生成的氢氧化镁晶体的体积，降低膨胀能力；水泥浆体中的碱性环境会抑制氧化镁膨胀剂的水化；高温养护有助于氢氧化镁的原位生成并使晶体致密，有助于膨胀发展。

英文摘要：

The hydration products and expansion characteristics of MgO expansive agents（MEA） with different chemical activities at different hydration ages and temperatures were investigated by X-ray diffraction and scanning electron microscopy. The restricted expansion rate and mechanical properties of shrinkage-compensating mortar containing 6% MEA were determined. The hydration process, expansion properties and mechanism of MEA were discussed.The results indicate that a high hydration activity of MEA reduces the volume of brucite crystals and its expansive ability decreases. Alkaline environment in the Portland cement paste hinders the hydration of MEA. Elevated temperature curing contributes to the in-situ formation and compaction of brucite crystals, hence enhancing the expansion of MgO expansive agents.