制备工艺对镁质膨胀剂水化活性和微观特性影响研究

Influence of Preparation Process on Hydration Activity and Microscopic Properties of Magnesia Expansion Agent

针对混凝土开裂问题,添加镁质膨胀剂可有效减少甚至消除混凝土因干缩和温度差而产生的收缩,使混凝土具备优异的抗裂性能。为了确定合理的镁质膨胀剂煅烧工艺,研究了煅烧温度、保温时间、升温速率及冷却方式对镁质膨胀剂晶粒尺寸、微观结构及活化性能的影响。结果表明:煅烧温度对镁质膨胀剂的水化活性有决定性影响,随着煅烧温度提高,镁质膨胀剂晶粒尺寸不断变大,比表面积逐渐减小,晶格畸变逐渐减小,水化放热量及活性逐渐降低;相同条件下,煅烧保温时间越长,镁质膨胀剂晶体晶粒尺寸越大,比表面积越小,晶体结晶度越高,镁质膨胀剂水化活性越低;采用快速冷却方式,可以获得高活性镁质膨胀剂。

To solve the problem of concrete cracking,adding a magnesium expansive agent can effectively reduce or even eliminate the shrinkage of concrete due to dry shrinkage and temperature difference so that the concrete has excellent crack resistance. In order to determine a reasonable calcination process for preparing magnesia expansion agent,the effects of calcination temperature,holding time,heating rate,and cooling mode on the grain size,microstructure,and activation properties of magnesia expansive agent were studied. The results show that the calcination temperature has a decisive influence on the hydration activity of magnesia expansive agent. With the increase of calcination temperature, the grain size of magnesia expansive agent increases continuously,while the specific surface area,the lattice distortion,the hydration heat release,and the activity decrease gradually. As the calcination holding time is longer under the same conditions,the magnesia expansion agent has a larger crystal grain size,lower specific surface area,higher crystallinity,and lower hydration activity. By adopting the rapid cooling method,a high-activity magnesia expansion agent can be obtained.