关键词: 预应力锚杆, 腐蚀损伤, pH, O2, 电化学分析

Abstract: Prestressed anchor bars are widely used since it can effectively control the displacement between rock and soil layers and structures. Due to the complexity of geological conditions, prestressed anchor bars are corroded and damaged continuously during long service, and even failures. In this paper, the accelerated corrosion test was conducted in lab, and the evolution characteristics of apparent corrosion of prestressed anchor bars were qualitatively described. The corrosion damage mechanism of prestressed anchor bars under the synergistic action of pH and O2 was then analyzed by means of electrochemical test system. A time-varying model of corrosion current density based on acidic oxygen environment was developed. The corrosion degree was characterized by the corrosion amount per unit length. Furthermore, the relationship between the oxygen flux rate and corrosion amount per unit length was established. The results show that corrosion degree reached a threshold value with the increase of the oxygen flux rate. Based on the test data analysis, the polarization curves of typical prestressed anchor bars were obtained, and the corrosion behavior of prestressed anchor bars in different periods was investigated. It is found that there is no apparent passivation zone in the working part of the prestressed anchor bars, and the anode is always in the active state. Positive shift of corrosion potential in oxygen environment has been revealed, while the corrosion potential of the prestressed anchor bars in the non-oxygenated acid corrosion solution is negative shift, thus the corrosion resistance is poor. This study can provide analytical means and data support for damage evolution behaviors analysis of prestressed anchor bars in aerobic rock and soil environment.

Key words: prestressed anchor bar, corrosion damage, pH, O2, electrochemical analysis