煅烧工艺对MgO反应活性及微观结构的影响

大体积混凝土浇筑后,水泥水化放热,混凝土内部温度升高,降温过程中会产生温度收缩,容易造成开裂。氧化镁膨胀剂具有延迟膨胀补偿大体积混凝土温降收缩的作用,已经广泛应用水利工程建设中。氧化镁膨胀剂的膨胀特性主要与其反应活性相关,而氧化镁的反应活性取决于其微观结构,微观结构的形成与煅烧工艺直接相关。该文以菱镁矿为原材料,研究了粉磨细度、煅烧温度、保温时间对MgO反应活性和微观结构的影响,并建立了微观结构与反应活性的关系。结果表明,菱镁矿D_(50)为11.89μm煅烧后MgO活性较高,煅烧温度越高,氧化镁膨胀剂晶体尺寸越大,晶格畸变越小,反应活性越低。保温时间影响MgCO_3的分解,保温时间短,MgCO_3分解不完全;保温时间长,晶体尺寸增大,晶格畸变减小,反应活性降低。

Effects of Calcine Process to Reactivity and Microstructure of MgO

Crack of mass concrete that is created by temperature stress, which is a major factor affecting the quality of construction in the mass concrete construction.MgO as expansive agent to compensate shrinkage of cement paste has been widely applied to the water power engineering.Expansion characteristics of MgO expansive agent is mainly related to its reactivity, and the reactivity of MgO depends on its microstructure, the microstructure is directly related to calcine process.In this study, effects of the grinding fineness, calcination temperature, holding time on the reactivity and microstructure have been studied, and the relationship between microstructure and reactivity has been established.The results indicate that the crystal size is larger and the lattice distortion is smaller when the calcination temperature is higher, resulting in a lower reactivity.The holding time influence the decomposition of MgCO3.the decomposition of MgCO3 is incomplete when the holding time is short, and the reactivity of MgO is low.However, the reactivity of MgO is also low with long holding time.