Study On Process Of Mass Transportation And Reinforcement Corrosion Based On Damaged Concrete

Transport of chloridion is one of the most important factor in the durability of reinforced concrete since it directly determines when its depassivation starts and its corrosion rate.Because of its noticeable influence on the crack expansion and pore structure of concrete structure,the load level can change the transmission ability of the concrete structure.Due to significant value for the accurate prediction of the service life of concrete structures in the marine environment,it is meaningful to research into the transmission of chlorine salt in concrete and the reinforcement corrosion,which is the focus of this dissertation.The main points are:(1)The digital image correlation(DIC)technology was involved as the main tool for the measurement of the surface field of the reinforced concrete beams,and analysis of the cracking process of concrete girder under bending load.With the damage degree selected as a quantitative index for the evaluation of the damage state of concrete,and damage degree of the multi-axial stress taken into consideration,the relationship between the damage degree and secant modulus of concrete can be obtained based on the theoretical analysis.According to the definition of damage degree and the strain field measured by the DIC technology,this dissertation acquired the two-dimensional damage field distribution of reinforced concrete beam under bending load.It was found that the damage first appeared in the purely bent section and distributed unevenly along the longitudinal concrete beam.(2)The influence of load on the durability of reinforced concrete was studied based on the chloridion intrusion test on the four-point bending load with the dry and wet circulating chlorine environment.The influence of load on the diffusion coefficient of chloride ion was obtained by the determination of the concentration distribution of chloride ions at different positions on the concrete beam.This dissertation established a transmission model of chloridion that is influenced by both the multiple environments and external loadings.The major innovation of this model is the linkage between the load and the responses of structures based on the equivalent composite model.Thus,the output of strain value or damage degree can be used to establish the relationship between load level and chloridion diffusion coefficient.After the damage degree field being applied into the calculation of chloridioin transmission,the distribution field of chloridion under the influence of load can be obtained.(3)The analysis was conducted on the development of reinforcement corrosion under the combined effect of load and chloride,with the continuous measurement of corrosion potential and corrosion current density of steel in the virtue of the half-cell potential method and linear polarization method.According to the detection of steel bar by electrochemical method,positive correlations can both be observed between the corrosion rate of reinforcement and the experimental period,and between the corrosion rate of reinforcement and load level,under the condition of dry and wet cycle.Besides,due to the unevenness of steel surface and diversity of concrete materials,the probability and rate of corrosion are various.Therefore,a fuzzy probability model of corrosion rate is established based on electrochemical reaction kinetics.