Model Of Chloride Penetration Concrete Under The Drying And Wetting Cycles Coupled With Load

The durability of concrete structures has attracted extraordinary concern from the field of civil engineering. Chloride penetration into concrete seriously in drying and wetting zone, Before chloride penetration model ignore load effect and don't match test result. As a result of the problem, three hotspots on durability of concrete structures in chloride are involved. "Chloride penetration in unsaturated concrete", "Concrete moisture surface factor" "Effect of load on the durability of concrete. The content includes:(1) 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. Study the effect of drying and wetting cycles on chloride penetration by experiment, Test results showed a good correlation with the theory analysis results,(2) In the process of drying and wetting cycles, drying boundary conditions subject to environment and is difficult to determine moisture diffusion surface factor is the basic parameter to solve the drying boundary conditions in the moisture field of concrete .In this research, the third boundary condition of concrete moisture field was derived in considering the pore areas on concrete surface and pore moisture diffusion coefficient. The concrete surface moisture convection and diffusion processes were simplified as the convective mass transfer of incompressible fluid in one-dimensional flat wall. This research established a theoretical model on the moisture diffusion surface factor of concrete during the curing period based on the mass conservation and flat wall convective mass transfer principle. And an approximate solution of the model was provided. To verify the accuracy of the model, a series of simulation experiments were conducted and the test results showed a good agreement with the theory model calculation.(3) Analysis mechanism of loading impact chloride penetration into concrete; Consider the impact of load on the concrete porosity and average pore diameter, establish model of chloride penetration into concrete coupling with load. At last, design experiment of chloride penetration into loading concrete, analysis the result, test result is consistent with model conclusion. The research was financially supported by National Science Foundation (Grant No. 50838008), National Basic Research Program of China (973 Program, Grant No. 2009CB623200), Doctoral Program of Higher Education (No. 20070335087).