Acoustic Emission Monitoring of Pre-Stressed Concrete Beams During Accelerated Corrosion of Pre-Stressing Tendons

Abstract

Acoustic sensors attached to pre-stressed/post-tensioned bridges are promising tools for monitoring the progression of corrosion damage in pre-stressing/post-tensioning tendons. In this study, acoustic emission signals from a pre-stressed beam containing three pre-stressed tendons that were exposed to accelerated corrosion conditions were studied. A short length of each tendon was exposed, and a tank filled with the NaCl solution was placed over the exposed tendon. Over a period of several months, a corrosion current was driven into the tendons until at least one wire corroded through. Acoustic sensors were attached along the beam and were used to record acoustic emission events during the accelerated corrosion. At the termination of the accelerated corrosion experiment, the beam was sliced into sixty-two cross-sections, each being 5 cm thick. Each slice was inspected to correlate corrosion and tendon slippage with acoustic emission signals. Maps of the estimated origin of acoustic emission signals were compared with the maps of the position of tendon corrosion and slippage. The acoustic emission signals were correlated with the presence of wire fracture due to corrosion on the tendon and with proximity to the end of the beam. The larger emission signals are likely due to the loss of bond between the tendons and concrete, as tendon fracture due to corrosion was not found in any of the cross-sections. This work points to the use of acoustic emission to track the progression of damage in cases where corrosion has already resulted in tendon fracture, and progression is proceeding by loss of bond.