| Ordinary reinforced concrete structures will generally have cracks and micropores during use,which makes it easier for the corrosive medium to enter the inside of the reinforced concrete structure.If the corrosive medium reaches the surface of the steel bar,it will cause the steel bar to deteriorate.Therefore,reducing the corrosion medium such as chloride ions into the reinforced concrete or draining the corrosive medium in the reinforced concrete is an effective means to ensure the durability of the reinforced concrete structure.However,under certain conditions,concrete cracks have the characteristics of self-healing,thereby recovering and improving the performance of concrete to a certain extent;and in addition to the selfrepair of concrete itself,artificial electrochemical repair technology is used to make the chloride ion discharged from the concrete structure.A means of corroded concrete structures.Therefore,studying the influence of self-healing of cracks on chloride ion transmission,steel corrosion and electrochemical dechlorination also has engineering value and significance for studying and improving the service life of reinforced concrete structures.This thesis simulates the dynamic process of crack self-healing from two perspectives of chloride ion "intoexhaust" concrete,based on finite element software,in order to reveal the influence of crack self-healing on the durability of reinforced concrete structures.The main contents include:1)A mesoscopic model of chloride ion transport composed of aggregate,mortar,interfacial transition zone(ITZ),cracks and crack propagation zone(DZ)phases has been established.The dynamic crack self-healing process is simulated using moving grid technology.Analyzed and discussed the distribution of chloride ion concentration in the crack and DZ during the self-healing process,the influence of self-healing rate on the chloride ion concentration,and the influence of ITZ and DZ on the chloride ion concentration.It is found that the self-healing rate increases with time;the chloride ion concentration distribution of concrete considering the self-healing effect of cracks is gradually lower than that of concrete without considering the self-healing effect of cracks;the self-healing rate of cracks and DZ is The longitudinal chloride ion concentration has a significant effect;as the width or depth of the DZ increases,the chloride ion concentration distribution gradually increases;the thickness of the interface transition zone has a negligible effect on the chloride ion concentration distribution in concrete.2)Based on the moving grid technology,the process of dynamic self-healing of transverse cracks coupled with corrosion of steel bars was simulated,and the distribution and time-varying laws of the surface potential of steel bars and the influence of self-healing of transverse cracks on the corrosion rate of steel bars were explored.It is found that the surface potential of the steel bar where the transverse cracks are located is lower than other parts,and the surface potential of the steel bars continues to decrease with the extension of the erosion time;the self-healing of the transverse cracks not only reduces the corrosion rate and the surface potential of the steel bars,but also reduces chloride ions The diffusion rate in the concrete;the thickness of the protective layer and the self-healing rate of transverse cracks are negatively correlated with the corrosion current density on the surface of the steel bars;the initial width of the transverse cracks is positively correlated with the corrosion current density on the surface of the steel bars.3)The ion migration process of electrochemical chloride extraction in cracked selfhealing concrete was simulated,and the relationship between the distribution of chloride ion concentration and the factors affecting the electrochemical dechlorination process was discussed.In the initial stage of the electrochemical dechlorination process,the chloride ion content around the steel bar decreases sharply,while the hydroxide ion concentration rises sharply;when self-healing cracks appear in the anode area,the chloride ion concentration in the concrete decreases faster;the front end of the steel bar The rate of decrease of chloride ion concentration is slower than that when the crack is constant;different self-healing rates have little effect on the concentration of chloride ion in concrete for electrochemical dechlorination. |
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