In order to research the reason of crack appearing and strength reduction of special fine sand concrete, several espe-cial fine sand concrete specimens with different water-cement ratios are prepared and processed into electron microscope sam-ples. According to scanning electron microscope and energy spectrum analysis, the influence of variation of water-cement ratio on secondary interface microstructure of concrete is analyzed. The research result shows that the secondary interface microstruc-ture of concrete with lower water-cement ratio is relatively more uniform and compact, moreover, the Ca/Si ratio of C-S-H gels in secondary interface is different in concrete with lower water-cement ratio, but change little.%为探究特细砂配制的混凝土出现裂缝且强度降低的原因，配制了不同水灰比的特细砂混凝土并加工成电镜试样。通过电镜扫描及能谱分析来研究其二级界面微观结构，并分析水灰比的变化对二级界面微观结构的影响。结果表明：相对而言，水灰比偏低的混凝土二级界面微观结构更加均匀致密；不同水灰比的特细砂混凝土二级界面C-S-H的凝胶钙硅比不同，但变化不大；较低的水灰比可以改善特细砂混凝土二级界的微观结构。
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