强盐沼泽区干湿循环作用下桥梁桩基腐蚀损伤

为探明干湿循环与强盐沼泽腐蚀作用下桥梁桩基混凝土材料损伤机理，通过室内模拟试验，研究了不同材料质量比的混凝土浸入不同浓度复合盐溶液，经干湿循环后的质量损失率、相对动弹性模量和抗侵蚀系数；基于扫描电子显微镜(SEM)、能谱仪(EDS)和化学成分分析相结合的方法，研究了桩身混凝土抗腐蚀微观机理。研究结果表明：经干湿循环后混凝土质量增长是因为在材料内部生成了钙矾石、Friedel盐等膨胀性晶体，氯盐的存在能够抑制硫酸盐对于桩基混凝土的侵蚀作用；复合盐溶液浓度不同时，经过120次的干湿循环后，水泥、碎石、砂子、水、粉煤灰、减水剂、硅灰、膨胀剂质量比为327∶1 103∶767∶170∶87∶7∶22∶44(质量比Ⅲ)的桩基混凝土试件的相对动弹性模量为92.7%，抗侵蚀系数最小为0.91，而在未添加硅灰和膨胀剂的质量比与仅添加硅灰的质量比下桩基混凝土试件的相对动弹性模量最大为89.7%，抗侵蚀系数最小为0.80，质量比Ⅲ的桩基混凝土试件的抗侵蚀性能较好，桩基混凝土试件受到膨胀力但内部未产生裂缝，说明添加硅灰和膨胀剂提升了桩基混凝土的抗侵蚀能力且可以确保桩基混凝土不产生裂缝。可见，实际工程中可综合考虑区域内腐蚀性离子类别等因素，在质量比Ⅲ的基础上进一步优化桩基混凝土的质量比。

Corrosion damage of bridge pile foundations under dry-wet cycles in strong salt marsh areas

To investigate the damage mechanism of concrete material of bridge pile foundations under the action of dry-wet cycles and strong salt marsh corrosion, indoor simulation tests were conducted, and the mass loss rates, relative dynamic elastic moduli, and corrosion resistance coefficients of the concretes with different material mass ratios immersed in composite salt solutions with different concentrations after dry-wet cycles were studied. The corrosion resistance micro-mechanisms of the concrete in pile bodies were investigated by using a combination of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and chemical composition analysis. Research results indicate that the increase in concrete mass after dry-wet cycles is due to the formation of expansive crystals such as calcium aluminate and Friedel's salt in the material. The presence of chloride ions can inhibit the corrosive effect of sulfate ions on pile foundation concrete. When the composite salt solution concentration is different, after 120 dry-wet cycles, for the pile foundation concrete specimens with a mass ratio of cement, aggregate, sand, water, fly ash, water reducer, silica fume, and expansion agent as 327∶1 103∶767∶170∶87∶7∶22:44 (mass ratio Ⅲ), the relative dynamic elastic modulus is 92.7%, and the minimum corrosion resistance coefficient is 0.91. In comparison, the pile foundation concrete specimens without silica fume and expansion agent or only with silica fume have a maximum relative dynamic elastic modulus of 89.7% and a minimum corrosion resistance coefficient of 0.80. The pile foundation concrete specimens with mass ratio Ⅲ exhibit better corrosion resistance performance and have no internal cracks even when they are subjected to the expansion force, indicating that the addition of silica fume and expansion agent improves the corrosion resistance of pile foundation concrete while ensuring no crack appears in the pile foundation concrete. Obviously, the factors such as the category of corrosive ions must be comprehensively considered, and further optimization of mass ratio of pile foundation concrete material must be carried out based on the mass ratio Ⅲ in practical engineering. 6 tabs, 12 figs, 30 refs.