Mechanism Of Chloride Ions Transportation In Unsaturated Concrete

The chloride attack is always regarded as a consequential issue of deterioration in service performance of reinforced concrete structure and durability of those concrete structures, which lay a significant emphasis on the prediction in the life cycle of concrete structure service performance. Processing form the mechanism of chloride ions transportation in concrete, this dissertation discusses the mechanism of chloride ions transportation in unsaturated concrete under various circumstances, especially in drying-wetting environment, following the work that establishing and consummating the model of chloride transportation in unsaturated concrete under drying-wetting environment. The main research work as follows:Applying the principles of electrochemistry, in this paper mainly analysis the processes of convection, diffusion and electro-migration in their own transportation mechanism, transportation function and its coupling relationship with other procedure separately. A transportation function that processing in multi-mechanism is set up based the theory above.An distribution model of two-dimensional random concrete aggregates has created by adopting Fuller grading curve, which place a new method to research on how the chloride penetrate into concrete in microcosmic level. To ensure the two-dimensional random aggregates model could simulate accurately with the realistic environment, random vertex method is taken as a way to generate polygon aggregate shape and then use MATLAB program to code this model. Taking pore saturation as a coupling parameter, the transportation processes in unsaturated concrete is described by two different field, which are pore unsaturated water seepage field and chloride diffusion field. Based these two different fields, as well as the different water diffusion coefficient parameters in humid and arid condition, putting forward a non-linear model in these two different water condition. Combined with the coupling relationship between chloride diffusion processes and convection processes in unsaturated concrete, establishing a transportation model concerning of chloride ion in unsaturated concrete, ending up with presenting explicit scheme, implicit scheme and Crank-Nicolson scheme three different finite difference schemes about water transport equation and chloride transport equation.On account of the established chloride transport model in unsaturated concrete, the last part of dissertation is about to induce the two-dimensional concrete random aggregate model into a finite element software and considerably take advantage of a case to illustrate the mechanism of drying-wetting. The solution of this model and the experimental data agree well.