Degradation Behavior of Coral Concrete Exposed to Different Marine Environments

The durability of concrete exposed to the marine environment is a critical factor in structural design. This study examines the mechanical characteristics and deterioration processes of coral aggregate seawater concrete (CASC) when subjected to marine conditions. A laboratory-accelerated corrosion experiment was designed to simulate three kinds of immersion conditions, namely full immersion zone (FI), semi-immersion zone (SI), and salt spray zone (SS). The effects of immersion conditions and corrosion times on the mass loss, dynamic elastic modulus, porosity, and compressive strength were studied. According to the results, CASC corrosion was most severe in the SS and least severe in the FI for the same corrosion time. Moreover, tests like scanning electron microscopy (SEM) and X-ray diffraction (XRD) were carried out to investigate the degradation process of CASC. XRD and SEM results indicate that the CASC system’s early hydration improves strength, but late-stage expansion of ettringite and Friedel’s salt causes matrix cracking and strength reduction. Finally, a mechanism-based model and an empirical formula for the prediction of compressive strength of CASC were proposed.