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The damage process of concrete exposed to sodium sulfate attack and drying-wetting cycles was investigated. The water to binder(W/B) ratio and the concentration of sulfate solution were taken as variable parameters. Through the experiment, visual change, relative dynamic modulus of elasticity(RDME) and the surface damage layer thickness of concrete were measured.Furthermore, SEM and thermal analysis were used to investigate the changing of microstructure and corrosion products of concrete.The test results show that the ultrasonic velocity is related to the damage layer of concrete. It approves that an increase in damage layer thickness reduces the compactness and the ultrasonic velocity. The deterioration degree of concrete could be estimated effectively by measuring the surface damage layer and the RDME of concrete. It is also found that the content of gypsum in concrete is less than that of ettringite in test, and some gypsum is checked only after a certain corrosion extent. When the concrete is with high W/B ratio or exposed to high concentration of sulfate solution, the content of ettringite first increases and then decreases with corrosion time. However, the content of gypsum increases at a steady rate. The content of corrosion products does not correspond well with the observations of RDME change, and extensive amount of corrosion products can be formed before obvious damage occurs. 相似文献
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对水胶比为0.45的引气混凝土分别在质量分数为1% Na,SO4、5% Na2 SO4、5% MgSO4溶液及水中进行快速冻融试验,采用超声平测法测量混凝土损伤层厚度,分析了不同溶液中混凝土的损伤层、未损伤层超声波速及损伤层厚度随冻融循环次数的变化规律.结果表明:混凝土损伤层厚度能够反映硫酸盐-冻融共同作用下混凝土损伤程度;不同溶液与冻融共同作用下混凝土损伤程度有所不同,原因在于硫酸盐溶液对混凝土冻融破坏既存在抑制作用,又存在促进作用;随着硫酸钠溶液浓度的升高,硫酸钠溶液对混凝土的冻融破坏由促进作用逐渐转变为抑制作用,由于硫酸镁具有镁盐和硫酸盐的双重腐蚀,对混凝土的冻融破坏促进作用最大. 相似文献
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