Chloride Transport Model In Concrete Of Multi-mechanism And Numerical Simulation

The chloride corrosion of reinforcing steel in concrete structures or cement-based materials is a worldwide problem that affects the durability of a large number of reinforced concrete structures,which can cause serious economic problems or potentially dangerous and influence the function of structures.The major causes of reinforcement chloride corrosion in buildings are location in the coastal areas,in which the structures are consistently and accelerating affected by the sea breeze,sea waves,slat flog or tidal action.However,the concrete structures or cement-based materials are frequently served under the coupling function between the load and the environment conditions in the practical engineering.Therefore,study on chloride transport model in concrete of multi-mechanism,it is of great importance and practical significance to reveal the chloride ion transport properties of concrete under the action of multiple mechanisms,both for the durability design of new projects and for the durability evaluation of existing projects.The transportation process of chloride ion in concrete was divided into four types according to differences in external environment and transportation mechanism as:(1)Diffusion process which occurred in saturated condition.(2)Convection process which occurred in the unsaturated solution in the external environment or pore structure in concrete.(3)Electro-migration process which was according to the directional migration of chloride ion in concrete based on the influence of the direct-current electrical fields.(4)Chloride binding process which was produced in the pore wall in concrete.In this paper,each sub process are calculated and analyzed the occurrence condition,mechanism,transport model,and the coupling relationship between them.A transport model of chloride ion under the condition of diffusion,convection and electromigration is established and numerical simulated.In this paper,the transmission mechanism of chloride ion in concrete was determined according to the influence of load.A multi-mechanism transportation model was established based on the coupling relationship between load and chloride ion transport.The transport models are calculated and analyzed the influence of different load levels and time on the effects of chloride ion transportation of different mechanism based on the simple supported beam model under uniform load.The multi-mechanism models of chloride ion were discretized and calculated on the application of finite difference method in Nicholson’s difference scheme.The calculation results on finite difference method were used for analyzing the effect of different mechanisms on the transportation of chloride ion in concrete.