Characteristics Of Corroded Rebars Induced By Chloride Ion In Cracked Concrete Structures And Its Life Prediction

Rebar corrosion is the key factor that leads to the deterioration of bridge structures' durability.Rebar corrosion is not only related to the service function and structural resistance of reinforced concrete structures,but also closely related to the sustainable development of social,environmental and economic resources.Therefore,it is of great practical significance to analyze the rebar corrosion characteristics in reinforced concrete structures.In the process of long-term service,concrete material will be cracked due to the natural environment load(such as freeze-thaw cycles,carbonation)and the function of the reciprocating mechanical load.So,after dissolving in snow water,the deicing salt spread in winter will gradually penetrate into the bridge structure,which destroys the stable passivation environment of the rebar and leads to steel corrosion.Therefore,in order to clarify the corrosion characteristics of rebar in cracked concrete structures under chloride permeation and to predict the service state of cracked concrete structures,the major works carried out in this paper are as follows:(1)Based on the actual concrete aggregate distribution,the cracked concrete was regarded as a four-phase composite medium model.Based on indoor experimental data and the theoretical equation of mass transfer,the diffusion characteristics of chloride ions in cracked concrete were analyzed by the numerical analysis method.Besides,chloride ion mass transfer characteristics effect by different properties such as crack width,frequency and buckling degree were explored,and the influence significances of each factor are quantified based on the statistical method.(2)According to actual concrete pore fluid composition,the electrolytes with different pH values were prepared by means of cement extracting solution and deionized water to simulate the concrete material environment with different carbonation degrees.The electrochemical measurement technique was utilized for monitoring the formation and failure of passive film of rebar,and the critical chloride ion concentration at the time of steel passivation film failure occurred under different environmental conditions was studied.(3)Based on the numerical model,the prediction equation of chloride ion concentration in cracked concrete was established.Besides,by using the relationship between the critical chloride ion concentration of reinforcement corrosion and the pH value of concrete pore fluid and the established prediction equation of chloride penetration,a method for evaluating the service status of reinforced concrete structures was proposed.