Corrosion Damage Behavior of Prestressed Rock Bolts under Aggressive Environment

Abstract

The corrosion of prestressed rock bolts (PRBs) has become a serious problem threatening the durability of prestressed anchorage structures during their service. This paper aims to investigate the corrosion damage mechanisms of the free lengths of PRBs subjected to an aggressive environment. During the experiment period, the corrosion behavior of the rock bolts was analyzed considering the influence of prestress under different pH (4, 5, 6, 7, and 8) amounts and several oxygen flow rates (OFR, 0 cm3/min, 40 cm3/min, 80 cm3/min, 120 cm3/min, and 160 cm3/min). Based on the electrochemical analysis, a corrosion rate (CR) development model of the PRBs related to the OFR was developed. The results indicated that the prestress had a great influence on the corrosion of the rock bolts. In the process of corrosion, the PRBs were in an activated state, and no passivation region was formed all the time. The corrosion degree of PRBs increased remarkably with an OFR ranging from 0 cm3/min to 80 cm3/min, and then it reached a threshold value. Additionally, the CR increment was insensitive to the OFR when the pH value was constant. It was observed that the loss rate of the ultimate elongation was larger than the other mechanical properties such as the ultimate tensile load loss rate and the elastic modulus. The effective stress loss of the PRBs under different conditions indicated that more attention is needed to be given to the specimens immersed in solutions with an OFR greater 40 cm3/min and pH lower than 6.