| Chloride ion penetration is one of the important factors to influence the durability of RC members. The penetration of chloride ion into concrete will make steel bars rust, and reduce carrying capacity of RC member, and endanger the safety of RC structures or members in short time.Based on former studies and practical background projects, it is a series of erosion tests of RC girders under flexural loading has been designed and carried out. The influence of the effect of durative flexural load on chloride diffusion in concrete has been analyzed, and the rule of some capabilities of members such as durability capacity has also researched in this paper. Based on Fick's second law and a random method, corrosion initial time of steel bars and the influence factors of the erosion time have been analyzed.The main conclusions are listed in this paper:1. The level of loading has an obvious effect on chloride diffusion and concentration distribution of chloride ions in tensile zones in concrete of the testing girders. In all the corrosion girders, there exist obvious convection zones, which is similar to the concrete members exposed to the natural eroding environment.2. The concentration of chloride ions in press zones decreases with the increase of load, but with the extent of the load, the amplitude decreases. and the condition is opposite in tensile zone. The effect of flexural tensile stress to chloride erosion is particularly obvious. As the flexural loading reaches 45%Fmax, the diffusion coefficients is 8.2 times more than that without loading.3. The erosion girders under loading, the rate of bars rusting increase with the increase of erosion time after the steel rusted, while both the limited durability capacity of girders and crazing loading decrease. When the rate is lower, the decrease of limited durability capacity is not obvious, but the crazing loading decreases fast. Prolong the curing time, and the crazing time postpones. There is good correlativity between the coefficient of crazing loading and the rate of bars rust.4. The mix proportion of water and cement has obvious influence on the chloride diffusions of the concrete under flexural loading, but the effect of curing time is smaller.5. In the designed test environment, the chloride threshold value for corrosion of steel bars in tensile zones of concrete girders under loading is related to the curing time. The chloride threshold value for corrosion of steel bars in tensile zones for test girders of curing time 28d is 0.10%~0.22% ,and that is 0.17%~0.29% for test girders of curing time 56d .6. It is indicated in the test that the chloride threshold value for corrosion of steel bars of the girders for curing time 56 d is higher than that of test girders for curing time 28 d. Prolong the conserving time, the corrosion initial time of steel bars in concrete is extended. |
