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.

Concrete structures are common in marine engineering, such as port wharves, sea crossing bridges, drilling platforms, and island reef revetments. Concrete structures exposed to tides/splashes for long periods are susceptible to seawater dry–wet cycles, which may lead to structural cracking during their service life. To ensure the safety and service life of concrete structures, cracks must be addressed with repairs or reinforcements. Numerous studies have shown that the concrete crack surface morphology determines the repair and reinforcement effects and affects the interfacial bonding performance, mechanical properties, and durability. Therefore, studying the surface morphology variation patterns of concrete cracks under seawater dry–wet cycles is important for concrete repair and reinforcement. In this paper, we produce concrete cracks through splitting and conduct seawater dry–wet cycle tests on concrete crack interfaces under different seawater concentrations to study the 3D morphological characteristics of cracks under seawater dry–wet cycles and provide experimental data to reveal the concrete crack surface changes for future repair. This study could serve as a guideline for repairing cracks in concrete structures in tidal/splash zones.