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采用改进的非接触式混凝土收缩测定仪及标靶,研究了m(M)/m(P)比值(MgO与KH_2PO_4的质量比)对磷酸镁水泥石自收缩行为的影响,运用八通道微量量热仪、压汞仪、X射线衍射仪、扫描电子显微镜及能谱仪等分析手段,分析了m(M)/m(P)比值对磷酸镁水泥石自收缩的作用机理。结果表明,磷酸镁水泥石的自收缩呈现出3个阶段的特征,即早期的迅速收缩阶段、微膨胀阶段、收缩缓慢发展阶段。随着m(M)/m(P)比值的增大,由于磷酸镁水泥石的水化放热量降低,水泥石内部孔隙率增大,水化产物结晶度降低,水泥石结构疏松,所以,自收缩率减小。
The effect of m (M) / m (P) ratio (mass ratio of MgO and KH_2PO_4) on self-shrinkage of magnesium phosphate cement was studied by using improved non-contact concrete shrinkage tester and target. The effects of m (M) / m (P) ratio on the self-shrinkage of magnesium phosphate cement were analyzed by means of thermal analysis, mercury intrusion porosimetry, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The results show that the self-shrinkage of magnesium phosphate cement exhibits three stages, that is, the early rapid contraction stage, the micro-expansion stage and the slow development stage of contraction. As the ratio of m (M) / m (P) increases, the hydration of magnesium phosphate cement decreases, the porosity of cement increases, the crystallinity of hydration products decreases, and the structure of cement is loose. Self shrinkage decreases.