An Experimental Study on the Deterioration Behaviour of External Tendons Due to Corrosion

An external tendon failure of the PSC box girder was found due to corrosion in South Korea, and the maintenance authorities promoted a study on evaluation and maintenance methods. One of their concerns was to confirm that the tendons were constantly available through repair when voids or minor corrosion were found in ducts. This study, thus, conducted external tendon experiments with insufficient grout filling and corrosion, and the resulting decrease in deterioration behaviours was investigated. The corrosion was accelerated during the experiment, and the strains and prestressing force were measured. The test results indicated minimal reductions in prestressing force and strain as the corrosion was induced, followed by significant fluctuations when a corroded wire ruptured. Prior to the rupture, the strain development was approximately 130 µε. However, after the rupture, the strain increased significantly, reaching a maximum of 4,296 µε in compression and 2,776 µε in tension. It was also confirmed that enough grout ratio to strands resulted in meaningful stress redistribution among the strands and that the wire rupture caused various strain development due to impact load. Based on the test result, a method for corrosion monitoring after re-grout was also proposed using low-power sensing and strain gauges.