The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion; however, the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear. To address this issue, novel sulfate transport and mesoscale splitting tests were designed, with a focus on considering the differences between the interfacial transition zone (ITZ) and cement matrix. Under the influence of stray current, the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack, while the tortuous and blocking effects of aggregates almost disappeared. This phenomenon was termed the “stray current-induced ITZ effect.” The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times, while the difference in splitting strength ranged from 1.56 to 1.64 times. Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry (PIV) technology, the mechanical properties were exposed to the consequences of the stray current-induced ITZ effect. The number of splitting cracks in the concrete increased, rather than along the central axis, which was significantly different from the conditions without stray current and the ideal Brazilian disk test. Furthermore, a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed. The embedded finite element calculation exhibited excellent agreement with the experimental results, indicating its reliability and accuracy. Additionally, the stress field was determined utilizing analytical methods, and the mechanism underlying crack propagation was successfully obtained. Compared to the cement matrix, a stray current led to more sulfates, more microstructure degradation, and greater increases in thickness and porosity in the ITZ, which was considered to be the essence of the stray current-induced ITZ effect.

中文翻译：

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揭示杂散电流诱导的界面过渡区 （ITZ） 对混凝土中硫酸盐腐蚀的影响


硫酸盐富集地区的轨道交通面临杂散电流和盐腐蚀的共同影响;然而，在这种情况下，硫酸根离子传输和混凝土降解机制仍不清楚。为了解决这个问题，设计了新颖的硫酸盐传输和中尺度劈裂测试，重点是考虑界面过渡区 （ITZ） 和水泥基体之间的差异。在杂散电流的影响下，ITZ 在调节硫酸盐攻击的输运和机械破坏过程中发挥了关键作用，而聚集体的曲折和阻塞作用几乎消失了。这种现象被称为“杂散电流诱导的 ITZ 效应”。实验数据表明，ITZ 导致的硫酸根离子传输差异在 1.90 到 2.31 倍之间，而分裂强度的差异在 1.56 到 1.64 倍之间。通过劈裂实验的实时同步和微秒响应粒子图像测速 （PIV） 技术，将力学性能暴露在杂散电流诱导的 ITZ 效应的影响下。混凝土中劈裂裂缝的数量增加，而不是沿中轴线增加，这与没有杂散电流的条件和理想的巴西盘测试明显不同。此外，精心构建了包含反应性和电扩散的硫酸根离子传质模型。嵌入式有限元计算与实验结果表现出极好的一致性，表明其可靠性和准确性。此外，利用解析方法确定了应力场，并成功获得了裂纹扩展的机制。 与水泥基体相比，杂散电流导致 ITZ 中硫酸盐增加、微观结构降解增加、厚度和孔隙率增加增加，这被认为是杂散电流诱导的 ITZ 效应的本质。