Mix Design For High Performance Concrete And Durability Contral For Concrete Structure In Chloride Environment

Steel corrosion caused by chloride erosion is the main reason of premature failure of concrete structures, especially in chloride environment. It is critical how to improve the durability of concrete so that it satisfies the design service life. A multi-factor model for the chloride diffusion coefficient and a mix design method for high performance concrete (HPC) are proposed in this paper, and a finite element method (FEM) for durability contral of concrete structures in chloride environment is established. The major jobs of this paper are shown as follows:1. The main factors which affect the chloride diffusion coefficient were confirmed based on single factor analysis between chloride diffusion coefficient and each factor. A multi-factor model for chloride diffusion coefficient was established considering the fact that the water-binder ratio(W/B) and mineral admixtures(fly ash, slag and so on) can affect chloride diffusion coefficient collectively based on RCM test data collected and the least square method. Test of goodness of fit and significance prove that the model have good universality.2. A mix design method which can meet the requirements of strength and chloride diffusion coefficient limit is proposed by bringing in multi-factor model for chloride diffusion coefficient and model for attenuation coefficient of age based on traditional mix design method. A mix for high performance concrete (HPC) which can ensure strength and the ability of resist chloride ion erosion can be designed effectively using this mix design method. The test results indicate concrete prepared using this mix can meet the requirements of strength and chloride diffusion coefficient limit simultaneously.3. Finite element method for durability contral of concrete structure in chloride salt erosion environment is established. The method ensure the chloride diffusion coefficient limit which can meet durability target and service life using finite element method (FEM) for chloride ion diffusion and monte-carlo finite element method (MCFEM) for degree of reliability calculation, then adjust the mix to meet the requirements of chloride diffusion coefficient limit based on high performance concrete (HPC) mix design method resist the erosion of chloride salt. On this basis, the service life of concrete structure in chloride salt environment is met.