杂散电流-盐冻耦合条件下混凝土的劣化

针对北方沿海及西北盐碱地区轨道交通工程中杂散电流-盐冻耦合作用的严酷环境,设计了杂散电流-盐冻耦合条件下混凝土抗冻性能试验及氯离子侵蚀试验,通过不同冻融循环次数后的混凝土质量损失率、相对动弹性模量、水溶性氯离子含量、氯离子扩散系数和盐浓度梯度表征了此耦合条件下混凝土劣化的基本特征,并通过压汞(MIP)、电镜扫描(SEM...

Concrete Deterioration under Coupling Condition of Stray Current and Salt-freezing

Rail transport engineering in the northern coastal and northwestern saline-alkali areas is suffering from the extreme environment of stray current and salt-freezing.Consequently,experiments of concrete resistance to freeze-thaw and chloride ion erosion under the coupling condition of stray current and salt-freezing were designed.The concrete mass loss rate,relative dynamic elastic modulus,water soluble chloride ion content,chloride ion diffusion coefficient and salt concentration gradient of concrete after different freeze-thaw cycles were measured to evaluate the concrete degradation under this condition.Analyses of MIP and SEM-EDS were employed to investigate the mechanisms of concrete deterioration induced by stray current effect under this condition.The results show that,compared with the condition of salt-freezing,the concrete specimens are deteriorated more seriously under the coupling condition of stray current and salt-freezing.The effect of stray current increases the salt-freezing damage and the chloride ion erosion to the specimens,which deteriorates the concrete pore structure,and accelerates the corrosion of the steel bar in the concrete.Additionally,the deterioration on the specimen surface is more significant than that on the steel bar surface.The mechanism of the concrete deterioration aggravated by stray current effect under this condition mainly lies in accelerating chloride ion migration,inducing hydration products decomposition and accelerating steel bar corrosion.