Prediction Models Of Steel Bar Corrosion Rate In Concrete Member

Corrosion of steel bar in concrete is one of the main factors affecting the durability of reinforced concrete structure. Corrosion mechanism, corrosion rates prediction, and the relativity of steel bar corrosion rates in artificial climatic laboratory and natural climatic environment have been in the highlight of the concrete field all over the world. In this paper, base on the rationale of steel corrosion, the electrochemistry model of steel bar corrosion, the corrosion rate of steel bar at flexure crack and the longitudinal crack, the infection of the distributed steel bar of section in concrete member, the prediction model of steel bar corrosion rate under nature climatic environment, and the corrosion detector which can be imbed in concrete member, were studied. The research findings enable to provide a scientific basis for the evaluation of reinforcement corrosion and the design of concrete durability.When the steel bar is corroding, the water and oxygen must be existed in the interface between the steel bar and the concrete. Under high humidity environment, the liquid state water can be formed in the pore around the steel bar and the corrosion rate of steel bar is controled by the diffusion of oxygen. The electrochemistry model is deduced which take the thickness of liquid state water and the area of oxygen diffusion into account. Base the polarization characteristic of the corrosion cathode, consider the influence of the concrete resistivity, the prediction model of corrosion rate under low humidity environment is deduced. The experimentations are also done to confirm the accuracy of the models.Base on the study of distribution characteristics of corrosion rust, the main corrosion mechanism is analysed around the reinforced section. The prediction model of corrosion rate at the corrosive expanding crack is also developed, and the relativity between corrosion rate with crack width is analyzed.Based on experiments, the regress model between the damage length, which the water and oxygen can easily reach, with the crack width and spacing is developed. The prediction model of corrosion rate around transverse crack is also found and the experimentations are also done to confirm the accuracy of the models.The corrosion specificity and the corrosion rate of deformed and plain steel bar are studied, the corrosion rate is influenced by inside inactivation steel bars and the stirrup steel is also considered. The general corrosion model of steel bar in concrete member is found. In nature climate environment, it is difficult to calculate the corrosion rate because the temperature and relative humidity are changed with the time. To build the model, equivalent temperature and relative humidity is used, and the corrosion model is found.Base on the principle of the"linear polarization"technology, a corrosion detector which can be imbed in concrete member, was also studied in this paper. The experimentations show that the test results of the detector are similar to the test result of GECOR8. The can be used for monitoring the corrosion rate of the steel bars in the concrete members.