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为合理确定混凝土中的MgO外掺量,通过室内试验测定了不同MgO外掺量的硬化水泥净浆、水泥砂浆的压蒸膨胀率,并对压蒸后的试样进行压汞试验、扫描电镜分析、背散射电子分析和X射线能谱分析。结果表明,MgO的掺量明显影响试样的密实度和孔隙结构。当MgO外掺量大于一定数值后,水泥浆、水泥砂浆的压蒸膨胀率发生显著增长,孔隙率明显增大,孔隙结构逐渐劣化。同时,水泥砂浆容许的MgO掺量多于水泥净浆,即利用水泥砂浆压蒸试件测得的MgO极限掺量比水泥净浆多。
In order to reasonably determine the content of MgO in concrete, the steam expansion coefficient of hardened cement paste and cement mortar with different MgO contents were determined by laboratory tests. Analysis, backscattered electron analysis and X-ray energy spectrum analysis. The results show that the content of MgO significantly affects the compactness and pore structure of the sample. When the content of MgO is greater than a certain value, the steam expansion coefficient of cement grout and cement mortar increase significantly, the porosity increases obviously, and the pore structure gradually deteriorates. In the meantime, the allowable MgO content of cement mortar is more than that of cement mortar, that is, the MgO limit content is higher than that of cement mortar measured by using the mortar pressure steaming test piece.