Assessing Corrosion Damage in Posttensioned Concrete Structures Using Acoustic Emission

The ingress of chlorides into posttensioned (PT) concrete structures is a leading cause of corrosion of the prestressing strands. This reduces the strength, durability, and service life of the structure and may result in catastrophic failure. A structural health monitoring (SHM) method is needed to improve the maintenance procedures associated with this method of construction. To evaluate the potential of acoustic emission monitoring for this application, long term corrosion monitoring tests were performed on specimens that were representative of internal and external posttensioning methods. Corrosion was induced in the specimens by adding chlorides to the grout and by performing wet/ dry cycling with NaCl solution. The corrosion process was monitored by half-cell potential measurements (HCP) and acoustic emission (AE). Results show that AE has the ability to detect corrosion damage in the PT specimens with similar accuracy to HCP measurements. Furthermore, intensity analysis of the AE data shows that the damage in the PT specimens can be categorized according to the level of corrosion present. This investigation demonstrates that AE can be successfully implemented to detect, monitor, and quantify corrosion levels in PT concrete structures, and that AE is a promising nonintrusive method to detect and quantify corrosion in the absence of electrochemical techniques. (C) 2015 American Society of Civil Engineers.