IntroductionThe South China Sea islands and reefs have emerged as key regions with far-reaching implications in multiple domains, including national defense, maritime trade, resource exploration, and ecological conservation. The rapid expansion of infrastructure in this area has made concrete structures the predominant choice due to their versatility and strength. However, the local environment presents an array of formidable challenges. The durability of these structures is thus under constant threat, with potential consequences for the integrity and functionality of the entire infrastructure network. Understanding and enhancing the durability of concrete structures in such a harsh environment is not only essential for the immediate success of ongoing projects but also for the long-term sustainable development and strategic positioning of the South China Sea islands and reefs.MethodsTo comprehensively study the durability and service life of reinforced concrete structures in the South China Sea islands and reefs environment, a long-term exposure test station was established in this area. This test station was designed to closely simulate the actual environmental conditions of the South China Sea islands and reefs, providing reliable test conditions for studying the durability of concrete structures.In the experiment, different types of concrete specimens and components were prepared. These included specimens with different corrosion inhibitors and different concrete strength grades. Electrochemical tests were carried out to monitor the corrosion status of reinforcing bars. The natural corrosion potential and polarization resistance of the reinforcing bars were measured using advanced electrochemical testing equipment. Mechanical property tests were also performed to evaluate the mechanical performance of the concrete structures. Compressive strength, flexural strength, and tensile strength tests were conducted on the concrete specimens and components. Chloride ion content analysis was carried out to understand the penetration and distribution of chloride ions in the concrete. The ChaDuraLife model was used for service life prediction. This model takes into account various factors such as chloride ion diffusion, concrete strength, and environmental conditions to predict the service life of the concrete structures.Results and discussionThe experimental results showed that different corrosion inhibitors had different effects on the corrosion of reinforcing bars in concrete. The SBT-KLJ(IV) hydrophobic pore-filling agent (HPA) exhibited excellent anti-corrosion performance. After 1227 d of corrosion, the natural corrosion potential of the steel bars in the concrete specimens with HPA shifted positively, and the polarization resistance continuously increased during the erosion period from 365 d to 730 d. In the chloride ion erosion environment of the islands and reefs, adding HPA reduced the chloride ion content on the concrete surface by approximately 59.9% compared to concrete without the corrosion inhibitor.The mechanical property tests of the concrete components after on-site exposure experiments indicated that the durability of concrete structures with different strength grades varied significantly. C80 concrete showed better resistance to seawater erosion and mechanical properties than C50 concrete. The service life prediction results based on the ChaDuraLife model demonstrated that adding a rust inhibitor or increasing the concrete strength grade could effectively extend the service life of the reinforced concrete structure in the splash zone environment of the South China Sea islands and reefs. The HPA rust inhibitor was particularly effective, and under certain conditions, it could extend the service life of the concrete structure to over 50 years.ConclusionsIn conclusion, the research findings have several important implications. The HPA corrosion inhibitor has demonstrated excellent long-term stability and anti-corrosion performance in the South China Sea islands and reefs environment. Its ability to enhance the electrochemical stability of reinforcing bars and reduce chloride ion permeability makes it a preferred choice for marine engineering applications. The significant improvement in the durability of concrete structures with HPA inhibitor has been clearly established through experimental and modeling results. The differences in durability among different strength grades of concrete highlight the importance of appropriate material selection for the specific demands of the South China Sea islands and reefs infrastructure. C80 concrete's superior performance in terms of chloride ion resistance and mechanical properties indicates its suitability for critical structures where enhanced durability is required. The comparison with the national standard emphasizes the need for further research and innovation to develop more effective strategies for improving the durability of reinforced concrete in this harsh environment. This could involve exploring new admixtures, optimizing concrete mix designs, or enhancing construction and maintenance practices. The data and insights obtained from this study provide a solid foundation for future research and engineering applications, guiding the design and construction of more durable concrete structures in the South China Sea islands and reefs. Ultimately, these efforts will contribute to the long-term safety and functionality of the infrastructure in this strategically important region.