3D Morphology Characteristics of Concrete Interfaces under Seawater Dry–Wet Cycles

Cracks are inevitable in concrete structures, and the deterioration of concrete crack interfaces in intertidal zones is often accelerated due to seawater dry–wet cycles. This paper aims to analyze the morphology and deterioration of crack interfaces under seawater dry–wet cycles. First, concrete crack surface specimens were obtained through splitting tests. Then, the specimens were placed in seawater solutions of different concentrations to undergo seawater dry–wet cycles. Furthermore, three-dimensional (3D) laser surface profile scanning was performed on the specimens after 0, 10, 30, and 60 seawater dry–wet cycles. Finally, the changes in morphological parameters were analyzed and calculated to derive the effect patterns of seawater dry–wet cycles on the 3D morphology of concrete crack interfaces. The results showed that the crack surface deterioration of the specimens in clear water was only affected by the dry–wet cycles, while that in seawater was jointly affected by seawater erosion and dry–wet cycles. The crack surface deterioration of the specimens in seawater can be divided into two stages. In the first 10 seawater dry–wet cycles, the chemical products generated by seawater erosion played a dominant role. The 3D morphological parameters and 3D fractal dimension changes of the specimens in seawater showed opposite trends to those in clear water. From the 10th seawater dry–wet cycle, erosion and flaking by the dry–wet cycles were dominant. The changes in the 3D morphological parameters and 3D fractal dimension of the specimens in seawater were consistent with those in clear water. Moreover, higher seawater concentrations led to more significant trends in the crack surface 3D morphological parameter and 3D fractal dimension changes.