The Transmission Mechanism Of The Chlorine Ion In Concrete

The durability of concrete stroctures has attracted extraordinary concern from the field of civil engineering. Besides the cost of rebuilding and maintenance,it is also related to the protection of environment and the sustainable development of society. The durability of concrete structures in marine environment is focus of the concern for the serious corrosion of reinforcement in concrete caused by chloride penetration. The issues of the durability of concrete structures in chloride environment before corrosion initiation are in fact the issues of chloride ions penetrating into concrete. As a result,the transportation model of chloride into concrete is taken as the axes, "The model of chloride ion into the concrete in unsaturated state"and so on,are studied in this paper by the program "The experimental study of high-speed railway engineering materials and structure durability", which is funded by The Ministry of Railways of China (2008G031-31), Main results are as follows:(1) According to the discrete characteristic of ions transport process into concrete and the heterogeneity of the concrete material, the application of Fick diffusion theory into engineering is limited greatly, and the convection-diffusion theory is considered more adaptive in this report due to its statistical property.Introduce the theory of diffusion and convection,Establish model of chloride penetration in unsaturated concrete and consider diffusion coupling with convection of pore solution, the Implicit Format of Finite Difference Method is engaged to solve the calculation of the numerical model.(2) Through Using Fourier analysis to discusse the stability of the different Format of Finite Difference Methods, Determine the stability condition of the different formats.(3) The dry-wet cyclic and spray experimental method is designed to imitate the transportation of chloride ion into the concrete at nature environment.The tests performed on the exposed specimens were the colorimetric tests with silver nitrate solution for the checking of the penetration depth of Cl-ion and the chemistry titration method for Cl" ion concentration profile. The model boundary conditions on the different environmental conditions are determined by the data fitting of the surface of chloride ion concentration.(4) The erosion processes of chlorine ion in concrete in dry-wet cyclic zone are analyzed by segmentation process. Using actual engineering testing data to verify this model, Compared the experimental results with model calculation results,The statistical characteristic analysis and the relativity of the calculated value and the measured value both verify the correction of the model.