The degradation of cement mortar subject to combined chloride ingress and sulfate attack under cyclic wetting–drying condition was studied through microstructural analysis. The specimens were exposed alternatively to a designated salt solution (NaCl, Na₂SO₄, or a mixture of NaCl and Na₂SO₄ solution) and air drying to simulate the natural conditions of tidal zones in the marine environment. Backscattered electron micrographs obtained with scanning electron microscopy showed three distinct layers formed from the surface inwards after exposure. The elemental distribution and phase composition of these layers were studied with energy dispersive spectroscopy through elemental mapping and point analysis, respectively. Phase changes after exposure were identified and compared among layers to understand the interaction between chloride and sulfate ions. The results showed a progressively layered degradation of cement mortar subject to the wetting and drying cycle, including a leaching zone, a deposition layer, and an inner area with relatively unaltered microstructure but with signs of ion penetration. Sulfate and chloride ions had mutual inhibiting effects on each other in cement mortar and the penetration depths of these two types of ions were different. A mechanism of progressively layered degradation of cement mortar under the investigating condition was proposed and discussed.

通过显微结构分析研究了在循环干湿条件下，水泥砂浆在氯化物侵入和硫酸盐侵蚀下的降解。将样品交替暴露于指定的盐溶液（NaCl、Na ₂ SO ₄或 NaCl 和 Na ₂ SO ₄的混合物）溶液）和空气干燥来模拟海洋环境中潮汐带的自然条件。用扫描电子显微镜获得的背散射电子显微照片显示曝光后从表面向内形成三个不同的层。分别通过元素映射和点分析用能量色散光谱研究了这些层的元素分布和相组成。识别暴露后的相变并在各层之间进行比较，以了解氯离子和硫酸根离子之间的相互作用。结果表明，水泥砂浆在干湿循环中逐渐分层降解，包括浸出区、沉积层和微观结构相对未改变但有离子渗透迹象的内部区域。硫酸盐和氯离子在水泥砂浆中相互抑制作用，两种离子的渗透深度不同。提出并讨论了研究条件下水泥砂浆分层降解的机理。