| Freeze-thaw damage and chloride ion erosion are the most representative problems in concrete durability. Marine concrete structures in cold regions often suffer the comprehensive effects of freeze-thaw action and chloride ion erosion due to the special serious environmental conditions. It has been obtained a lot of achievements from the experiments in the field of freeze-thaw action. At the same time, the research of the chloride ion diffusion was also concerned on the influence of steel bar in concrete. However, the research of comprehensive effects of freeze-thaw action and chloride ion diffusion on concrete is still not enough.In this thesis, a new chloride ion diffusion equation was deduced which contained most of the factors, such as, chloride ion binding capacity of concrete, time-dependence of concrete diffusivity and micro-defect of concrete structure and so on. Compared with other equations, it contains concrete degradation caused by freeze-thaw cycles action. And then, durability tests of concrete subjected to different freeze-thaw cycles and different contents of chloride ion were conducted. From the tests, the influence of freeze-thaw cycles and chloride ion on concrete materials was ascertained during the comprehensive effects. Finally, from the test results and theoretical analysis, a new constitutive relation of concrete subjected to freeze-thaw cycles immersed in seawater was gained and mechanical simulation by ABAQUS software based on the test was carried out.From this study, the research showed that when the concrete materials subjected to comprehensive effects of freeze-thaw cycles and chloride ion diffusion, because of the different content of chloride in concrete material, the concrete showed properties of layered degradation. The constitutive relationship could be more suitable to analyze the concrete structure in the cold region of the coast, which was enriched and developed the theory of concrete durability. |
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