Study On Transmission Model Of Chloride Ions In Concrete Under Marine Environment

Through the survey, it was found that quite a lot of concrete structures in marine environment had not reached the predicted service life before it cost massive money for maintain and reconstruction. It is the coaction of a variety of marine environmental factors that accelerate the transport of chloride ions from seawater into concrete, leading to steel’s electrochemical corrosion. At present, the concrete durability research is still in the stage of experiencing, and the chlorine ions transport model under wet and dry cycles is not complete yet.Based on the comprehensive analysis of existing research achievements and the mechanism of chloride ions movement, the marine chloride ions transport model under the influence of material properties and environmental factors was established. Taking an offshore wind farm project in East China sea as the engineering background, this present paper have studied chloride ions erosion discipline of thin walled structure in water level fluctuation area through the theoretical research and numerical calculation. Specific content as follows:1. By analyzing the durability breakage mechanism of the concrete structure and the material properties that influence chlorine ions transport and rebar corrosion, it is water cement ratio and the thickness of protection layer that are the key material factors affecting the service life of the structure.2. The chlorine ions transport process under multiple factors of marine environment is decomposed into some sub-processes, such as temperature conduction, water transport, chloride ions diffusion and convection. Through analyzing the mechanism, formula, conditions and coupling relationship of each process, the chloride ions transport model for marine environment is established.3. Considering the influence of solar radiation and tidal water level change on boundary conditions, the temperature field, humidity field and chloride ion concentration field for whole life cycle are simulated by FDM. Sunshine effect and dry-wet cycle can substantially accelerate the transport of chloride ions.4. Apply this model to analyze the distribution rule of chloride ion erosion with location, orientation, altitude. The absorption of sunlight in low latitudes is 3.08 times that in high latitudes. The average temperature at sunny side is 2.9 ℃ higher than that at dark side. The chloride ions concentration at convection zone increases with the altitude increases first and then decreases, probably reach 8 times.5. Finally evaluate the durability of an offshore wind power foundation in jiangsu, analyze the change rule of every physical field, and put forward several corresponding improvement measures.