Research On Corrosion Degree Detection Technology Of Reinforced Concrete Structure Based On Metal Magnetic Memory

The reinforcement corrosion inside the reinforced concrete structure will damage the structural performance,affect its durability and safety,and even lead to disastrous accident Therefore,the effective detection of Corrosion situation of reinforced concrete structures is the key to ensure the safety of service structure.The existing corrosion detection technology has been widely used in engineering.However,if the concrete protective layer is not cracked,the hidden rust will become difficult to be detected.The metal magnetic memory(MMM)method is a new environmentally friendly non-destructive testing technology that developed rapidly in recent years.The location and extent of damages can be determined by detecting the leakage magnetic of ferromagnetic materials.This method has not been used in corrosion detection of reinforced concrete structures,and it still needs some basic studies because of the short development time.Based on the MMM method,the theoretical analysis,experimental study and numerical simulation of the corrosion degree were carried out of steel bars in reinforced concrete structures.Then,the distribution characteristics of the self-magnetic leakage flux(SMFL)were analyzed,and the corrosion damage criterion of the steel bar was put forward.Ultimately,the preliminary research on the corrosion detection of reinforced concrete structures based on MMM method was carried out.Detailed contents and main conclusions are as follows:? Based on the analysis of the corrosion mechanism of reinforced concrete structure and magnetic charge theory,the analytic solution of reinforcement corrosion damage leakage magnetic field is deduced.? A comparative study on the corrosion detection of the single bare steel was conducted.The magnetic fields around the corroded steel bars were collected by scanning different paths.Some influential parameters on the distribution of SMFL were analyzed,such as the effects of different azimuths,the width and the degree of corrosion,the length of the steel bars and the lift-off height.Then,the distribution regularity of the signal was analyzed on the basis of the free magnetic field theory.? The coupling test of several steel bars was conducted.The results showed that the magnetic signals of several bars which were arranged together could be calculated by the vector superposition of each bar.Meanwhile,the distribution of bars in the concrete structure could be identified by the characteristics of the magnetic signals,the direction of which was perpendicular to the steel bars.? The experimental study on corrosion detection of reinforced concrete beams was carried out.The experimental results showed that the magnetic flux leakage signal of the test beam had the same characteristics as the bare bars.The tangential component of the SMFL signal was symmetrical with respect to the center of the corrosion zone,and up to the maximum,and the normal component was anti-symmetrical with respect to the center of the rust zone and passed through the zero point herein.Some influential parameters on the distribution of SMFL in corroded reinforced concrete beams were analyzed,such as the different degree of corrosion,arrangement of the stirrup,the diameter of the main bar and lift-off heights.The intersections of the tangential component distribution curves were proposed as the criterion of the corrosion zone.According to the linear correlation between the peaks of the tangential component and the corrosion depth,the corrosion degree of the steel could be determined.Then,the preliminary research on the detection of the corrosion in reinforced concrete structures based on MMM method was generated? The law of the SMFL for the corroded steel bar could be stimulated via the finite element software.The simulation results were in good agreement with the experimental results.Then,the reliability analysis of the corrosion degree in reinforced concrete structures based on MMM was carried out on the basis of the comparison between the results of magnetic load theory,the test and the finite element simulation.