Electrochemical Characteristic And Related Testing And Monitoring Technology Of The Steel Corrosion Of Concrete Structures

Reinforcement corrosion is the the main manifestation of durability failure of concrete structures. In this paper, the mechanism of reinforcement corrosion in concrete was revealed by using electrochemical impedance spectroscopy technique. Detection and monitoring reinforcement corrosion in concrete in chloride environment were studied. Refined chloride threshold quick test under an applied electric field. In addition, an Environment-related indoor accelerated test method to simulate the chloride penetration in sea level changing area for the first time, and the life prediction test method based on Multiple-Environmental-Similarity-Time (METS) theory was optimized.The main research contents in this thesis are as follows:1. According to the steel corrosion incentives, reinforcement corrosion induced by chloride penetration and concrete carbonation was considered. By using electrochemical impedance spectroscopy testing techniques, impedance spectroscopy characteristic of reinforcement in passivation and corrosion state was studied. The steel corrosion equivalent circuit models for chloride penetration and concrete carbonation were proposed, and the physical significance of each component in the circuit was explained. Finally, the equivalent circuit model was simplified.2. By analyzing polarization curve characteristics before and after reinforcement corrosion, pointing out the shortcomings of the commonly used polarization method, influence of the polarization test parameters and steel corrosion state and polarization surface area on polarization test was studied. According to the problems of polarization test, based on the principles of electrochemical polarization, a fast polarization method to determine steel corrosion was proposed. Based on this polarization method, through a large number of experimental data, the critical values of steel corrosion was determined, and the relationship with corrosion current density was established. Electrochemical frequency modulation testing techniques (EFM) was Firstly used in reinforcement corrosion reaserch to discuss polarization dynamics parameters range and correct calculation parameter B.3. Based on fast polarization method, a corrosion sensor monitoring chloride penetration was developed. Through indoor accelerated test, the sensor working performance was analyzed and the sensor structure was optimized. Based on the relationship between corrosion current density and chloride concentration, the method of monitoring chloride concentration in concrete was preliminarily studied.4. Research on rapid test determining chloride threshold was carried out. Reinforced polarization effect caused by Stray current was analyzed, clearing the method to determine the applied electric field voltage. Criterion to distinguish steel depassivation under continuous power condition was proposed. A natural penetration test and an electric field acceleration were designed to comparativly analyze chloride threshold under this two conditions, which verified the feasibility of the rapid test method.5. Based on monitoring the temperature and relative humidity inside concrete and reinforcement corrosion current testing, a theoretical model of dynamic prediction of steel corrosion output was proposed. Through indoor accelerated test, the relationship between temperature and relative humidity inside concrete and corrosion current density was established, and the test error of linear polarization method was modified, which verified the feasibility of this theoretical model of dynamic prediction. Related content gives an effective method to monitoring steel rust amount in concrete.6. Through analysis of chloride erosion mechanism within an alternate wetting-drying marine environment area, the main influencing factors was discussed. According to the erosion mechanism, an Environment-related indoor accelerated test method to simulate the chloride penetration in sea level changing area was proposed, and developed the tidal simulation test device. According to the field detection object, designing the relative indoor simulation test, correlation analysis between these two environments was carried out. For the alternate wetting-drying marine environment area, a simplified chloride penetration model was established to simulate indoor accelerated test by finite element method, which considering multiple factors. By combination of indoor accelerated simulation test, life prediction steps based on METS theory was optimized.