Experimental Study On Corrosion Rate Of Steel Bar In Double-doped Concrete Under The Salt Solution Environment

With the rapid development of cities, a large number of underground track engineering is emerging. Because the track built in the rock medium and the environment is complex. Track segments often work with initial damage in the early formation. In addition, the track will be under load, uneven settlement and other factors during the service. The initial damage will continue to deteriorate. Underground environment is rich in aggressive ions:chloride ion, sulfate ion and other ion. The diffusion of cracks provides a convenient channel for the harmful ion. The cracks eventually cause further deterioration of reinforced concrete structures. It leads to poor durability of the structure in the early stage. It is difficult to reach estimated service life. At present, the research of the law for concrete reinforcement corrosion under sulfate ions and chloride ions composite effect is relatively small. In this paper, take chloride ion, sulfateion, the width of crack and the thickness of the protective layer as the object of study. Study several factors that how to influence the rate of steel corrosion on the basis of experiments on theoretical analysis.The main contents of this paper are as follows:(1) Start from the importance of steel corrosion and summarizes the main factors affecting the steel corrosion in concrete. Analysis of the corrosion mechanism of steel in theory and summarizes several main research methods in steel corrosion.(2) Do accelerated testing by immersing in the solution. Measure corrosion potential, linear polarization curves, Tafel curves and other related electrochemical parameters by open circuit potential, linear sweep voltammetry and Tafel polarization curves. Through theoretical analysis, research results show that:the chloride ion is the main factors affecting steel corrosion. The probability of steel corrosion will be greater if the concentration of chloride ion is larger. Sulfate ions almost have no effect on the corrosion of steel in the initial erosion. Sulfate ions can restrain the corrosion of steel to some extent in the late erosion. Cracks can increase the probability of steel corrosion. The corrosion rate of reinforcing bars is greater if the width of crack is larger. The thickness of the protective layer is smaller. The probability of steel corrosion is greater.(3) Obtain polarization resistance Rp according to the linear polarization curve. Obtain B values from the Tafel polarization curve slope ba、bc. Obtain steel corrosion current density under various conditions. Do research in steel corrosion rate erosion under different environments.(4) Review some relevant results of existing concrete reinforcement corrosion rate model from the basic theory of electrochemical corrosion of metals. Measure reinforced corrosion current density values in a variety of conditions. Determine the corrosion current density model by fitting in a complex environment.