摘   要：针对大体积混凝土收缩开裂的特点，研究了煅烧菱镁矿所得MgO膨胀剂组成、微观结构、水化活性及膨胀变形性能，探讨了煅烧制度与MgO膨胀剂的微观结构、水化活性及膨胀性能的关系。结果表明，煅烧温度升高，MgO微晶聚集而成的MgO颗粒表面逐渐密实，团聚体中MgO晶体自由烧结程度提高、晶粒尺寸增大，水化活性值增大；相同粒度分布的菱镁矿粉体，煅烧温度对MgO膨胀剂粒度分布的影响基本一致。矿物组分、粒度分布基本一致条件下，水化活性值、晶粒尺寸与煅烧温度存在指数关系；水化活性值与晶粒尺寸存在线性关系。水化活性值可调控MgO膨胀剂的膨胀历程；不同煅烧制度制备的MgO膨胀剂的早期膨胀性能（水养20℃）随着活性值增大呈指数性减小。

Abstract: In order to improve the volume stability of mass concrete, the composition, microstructure, hydration activity and expansion property of MgO expansive agent obtained by calcining magnesite were investigated, and the relation between calcination systems and the microstructure, hydration activity and expansion deformation performance were discussed. The results show that when calcination temperature rises, the surface of MgO particles agglomerated by MgO crystallites will become denser. Since MgO crystals in agglomerations are sintered freely at a higher temperature, crystalline dimension is enlarged and hydration activity value is increased. Calcination temperature has similar influences on particles distribution of MgO expansive agent prepared from the same magnesite. When mineral constituent, particles distribution of MgO expansive agent are basically identical, an exponential relation exists between crystallite dimension and calcinations temperature, hydration activity value is proportioned with crystallite dimension. Hydration activity value can regulate and control MgO expansive agent’s expansion process, as the early expansion deformation performance (kept in water at 20℃) of MgO expansive agents prepared by different calcination systems will decrease exponentially along with hydration activity value increased.