ASSESSING CORROSION DAMAGE IN PRESTRESSED CONCRETE WITH ACOUSTIC EMISSION

Acoustic Emission (AE) sensing is employed to assess the presence and rate of steel corrosion evolving inside prestressing steel reinforced small-scale concrete specimens. Test setup consists of grade 6,000 psi concrete blocks with dimensions 4.5 x 4.5 x 20 inch (114 x 114 x 508 mm); a 30 inch (760 mm) long - ½ inch (13 mm) diameter strand is embedded in the concrete to serve as anode of the rapid corrosion cell. Specimens were either notched or unotched and 0.016 inch (0.4 mm) cracks were extended through the centerline of the specimens via three-point bending to analyze the effect of crack presence in byproduct development. The corrosion process is accelerated in a laboratory environment employing a potentiostat to supply a constant potential difference, 3% NaCl solution as electrolyte, and a copper plate beneath the concrete specimens served as a cathode. Impressed current, half-cell potential readings, linear polarization and AE data is compared to determine how accurate is acoustic sensing towards detecting in advance the on-set of corrosion and its progression. The initiation and propagation stages of corrosion are correlated with the percentage mass loss of steel and the energy acquired from the AE signal; this relation will be effective towards determining the residual service life of concrete structures in the field. Finally, locations of possible corroded areas are determined using the source triangulation option provided by AE technique