磷酸镁水泥基混凝土立面修补剂试验

Research and Engineering Application on Magnesium Phosphate Cement-based Concrete Patching Agent of Vertical Facade

目的研究磷酸镁水泥胶砂的收缩性、抗剪性能及抗开裂性能增长规律,为高层房屋外墙立面、桥墩立面、桥跨底面等特殊部位修补提供优化的组分配合比.方法通过水泥胶砂干缩试验研究氧化镁活性、水胶质量比、氧化镁与磷酸二氢铵质量比、粉煤灰掺量对MPC砂浆干缩应变的影响规律;外加剂掺和比对"水泥胶砂—基材"界面抗剪强度的影响规律以及聚丙烯纤维掺量对其抗裂性的影响规律.结果随着水胶质量比、氧化镁与磷酸二氢铵质量比的降低,MPC砂浆的干缩应变减小;随着粉煤灰掺量的增加,MPC砂浆的干缩应变减小,抗剪强度降低;随着聚丙烯纤维掺入量的提高,MPC砂浆正方形板状试样的裂缝数量减少,当纤维掺量达到1.5 kg/m^3时,其A_(cr)为0,η为100%.结论磷酸镁水泥基混凝土立面修补剂具有抗收缩抗开裂和高粘结性的特点,满足修补施工及耐久性要求.

To study the property of shrinkage and shear strength of Magnesium Phosphate Cement(MPC)and regulation of its crack growing and to provide the optimal mix proportion of Magnesium Phosphate Cement suitable for some special parts of buildings such as facade of high-rise buildings,bridge piers,and the bottom of bridge span,the dry shrinkage tests of cement mortar have been done.Through the tests,the effect of magnesia activity,water/cement ratio,magnesium/phosphorus ratio and the percent of the fly ash on the regulation of the shrinkage strain of MPC and the effect of admixtures on the shear strength of the'cement mortar—base material'interface and the effect of polypropylene fiber admixture amount on crack growing have been studied.The drying shrinkage of magnesium phosphate cement decreases with the increase of the activity of Magnesium Oxide,the decrease of water binder ratio,the decrease of magnesium phosphorus ratio and the increase of fly ash content.When the content of fly ash is 20%,it would be less drying shrinkage and higher shear resistance strength.The addition of polypropylene fiber can improve the crack resistance of magnesium phosphate cement based patching agent.When the fiber content reaches 1.5 kg/m^3,is 0,ηis 100%.In summary,while the MgO is 1 300℃,M/P is 4,Water/cement radio is 0.18,the Fly ash content is 20%,it can be applied to practical engineering and meet the construction and durability requirements.