【摘要】 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。更多还原

【Abstract】 The expansion characteristics of light-burnt magnesia （MgO） in several cement pastes were determined in this paper. By means of micro-calorimeter, DAT, DSC, XRD, OM and EM, the hydration of MgO and the crystallization characteristics of Mg（OH）₂crytals in NaOH solutions with different alkalinity and in cement pastes were investigated in more details. Based on the experimental results, an expansion mechanism of cements with MgO and a model of expansion were proposed. Expansion of cement with MgO results from the formation and the growth of Mg（OH）₂crystals. The expansion depends on the sites of Mg（OH）₂ crystals formed as well as on the sizes of them. Driving forces of the expansion are crystallization pressure brought about by growth of Mg（OH）₂ crystals and swelling pressure, which is caused by water adsorption of the Mg（OH）₂ crystals, but the latter plays a less important role. Slags and fly ashes reduce alkalinities of pore solutions of the cement pastes and increase the porosities of pastes, hence they restrain the expansion.更多还原