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本文探讨了轻烧镁砂(MgO)在不同水泥浆体中的膨胀特性,并借助于水化热仪、DTA、DSC、XRD、OM和EM对MgO在不同碱度NaOH溶液和水泥浆体中的水化及其产物Mg(OH)_2的结晶特性进行了较为详细的研究。在此基础上,提出了MgO在水泥中的膨胀机理,并据此建立了膨胀模型。研究结果表明,水泥中MgO的膨胀起因于Mg(OH)_2晶体的生成和长大。膨胀在很大程度上取决于生成的Mg(OH)_2晶体所占据的位置,其次还取决于Mg(OH)_2晶体的尺寸。浆体膨胀的直接推动力为极细小Mg(OH)_2晶体的吸水肿胀力和Mg(OH)_2晶体的结晶生长压力,但后者是主要的。粉煤灰和矿渣使浆体孔隙液碱度降低和浆体多孔是其对膨胀起抑制作用的主要原因。
In this paper, the swelling characteristics of lightly calcined magnesia (MgO) in different cement slurries are discussed. With the help of hydration heat meter, DTA, DSC, XRD, OM and EM, MgO is used in different alkalinity NaOH solutions and cement pastes. The hydration and the crystallization characteristics of Mg(OH)2 have been studied in detail. On this basis, the expansion mechanism of MgO in cement was proposed, and the expansion model was established accordingly. The results show that the swelling of MgO in cement results from the formation and growth of Mg(OH) 2 crystals. Swelling depends to a large extent on the position occupied by the resulting Mg(OH) 2 crystals, and secondly on the size of the Mg(OH) 2 crystals. The direct impetus of slurry expansion is the swelling swelling force of ultra-fine Mg(OH) 2 crystals and the crystal growth pressure of Mg(OH) 2 crystals, but the latter is the main one. Fly ash and slag can reduce the alkalinity of the pore fluid of the slurry and the porous body of the slurry is the main reason that inhibits expansion.