Ingress Of Chloride Ion And Corrosion Prediction Of Steel Bar In Concrete Under The Tidal Zone Of Tidal Reach Environment

The corrosion of steel bar has emerged as one of the most important issues leading to the durability deterioration of reinforced concrete structures in chloride environment.With the continuous ingress of chloride ions into concrete,the steel corrosion due to the damage of passive film on the steel surface will occur since the concentration of chloride ions accumulated to a critical value.Researches on the property related to chloride ion diffusion in concrete and predicting the effect of steel corrosion on structural durability are of great significance.Based on the long exposure experiment located in the tidal zone of macro-tidal reach and the laboratory simulation test of early-age concrete,the properties of chloride diffusion in concrete under both two environments were achieved,and the randomness of chloride erosion parameters in concrete were analyzed.On the basis of the experiment results,the corrosion initial time of steel bar in concrete which take the curing age and the time variation of chloride diffusion into account was analyzed.Furthermore,the design requirements of chloride diffusion performance related to the corrosion initial time in the durability ofconcrete under the tidal zone of tidal reach environment were proposed.The main contents of this study are as follows:1.According to the long exposure experiment in the macro-tidal reach environment and the measured free chloride concentration,the effects of water-cement ratio,types and contents of basalt fiber and exposure time on chloride ion diffusion in concrete were analyzed.On the basis of existing researches,the time-dependent models of chloride diffusion coefficient under this environment were updated,and the similarity of chloride ion diffusion in concrete under the artificial climate simulation tidal environment was analyzed.2.Based on the similarity theory,a laboratory simulation experiment on chloride diffusion in early-age concrete was designed and conducted.The influences of water-cement ratio,curing age and exposure time on chloride ion diffusion in concrete were analyzed,and the time-dependent models of chloride diffusion coefficient in early-age concrete were established.Meanwhile,the similarities of chloride diffusion performance of early-age concrete and 28-days age concrete under laboratory simulation experiment and the the long exposure field test were obtained,respectively.3.Through the chloride ion ingress tests under the simulated tidal environment and natural tidal environment,the time-dependent randomness of free chloride ion concentrations,chloride ion diffusion coefficients,the convection depths and the chloride threshold level in concrete withdifferent curing ages under different tidal environment were studied respectively.4.The Monte Carlo method was adopted to analyze the corrosion initial time of steel bar in concrete,and the similarity of the corrosion initial time of steel bar under different tidal environments was studied.The effects of the parameters including chloride environment,curing age and concrete cover thickness on the corrosion initial time of steel bar were analyzed.5.According to the design working life,environment classification and material characteristics of concrete,the comprehensive influence coefficients of chloride ion diffusion under the tidal zone of macro-tidal reach environment were analyzed,the basis parameters for structural durability design under tidal zone in tidal reach environment were researched.Based on the corrosion initial time of steel bar,the design requirements of chloride diffusion performance in concrete durability under the tidal reach environment were presented.