摘要
观察了不同水胶比内掺氧化镁膨胀剂补偿收缩砂浆在不同养护制度下(水中养护与密封养护)的自由膨胀率,并结合浆体孔隙率以及显微形貌观察,分析了在较长龄期中不同水胶比条件下的氧化镁膨胀剂的补偿收缩特性。采用XRD-Rietveld法测定不同水胶比条件下氧化镁膨胀剂的反应程度。结果表明:氧化镁膨胀剂发挥作用的最适宜水胶比为0.4,过高或过低都会降低补偿收缩砂浆的膨胀效果。密封条件会使其膨胀效应更早停止。低水胶比使浆体中缺水,因而MgO水化程度较低,同时使浆体结构致密,进而降低补偿收缩砂浆的膨胀量。高水胶比使得浆体内水分供给充足,MgO较快反应完全,进而使得补偿收缩砂浆的膨胀停止较早。
The free expansion rate of shrinkage-compensating mortar containing magnesium oxide expansive agents(MEA) with different water-binder(W/B) ratios was investigated under different curing conditions, i.e., saturated and sealed curing. The porosity and morphology of hardened pastes were investigated. The hydration degree of MgO in pastes with different W/B ratios was measured by X-ray diffraction-Rietveld method. The shrinkage-compensating characteristics of MEA in a relatively long term were discussed. The results show that the suitable W/B ratio is 0.4 for MEA to compensate the shrinkage of mortar. A higher or a lower W/B ratio both reduces the expansion of mortar. Compared to the saturated condition, the expansion of mortars cured in sealed condition stops earlier. A lower W/B ratio results in a densified paste and reduces the pore water quantity for MEA to hydrate, thus reducing the expansion of mortar. A higher W/B ratio provides sufficient water for MEA to hydrate, thus accelerating the MEA hydrates and stoping the expansion of mortar early.
引文
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