Longitudinal guided waves for monitoring corrosion in reinforced mortar

Abstract

Guided longitudinal modes in both low (<200 kHz) and high (2–8 MHz) frequency ranges were invoked to monitor damage in reinforced mortar specimens undergoing accelerated uniform corrosion. The fundamental longitudinal mode, i.e. L(0, 1), and the L(0, 9) mode were invoked for low- and high-frequency testing, respectively. Because of the significant amount of axial displacement at the steel/mortar interface, the L(0, 1) mode was so appreciably attenuated for the particular specimen size used that it is was not detected until after corrosion had initiated and corrosion product accumulation caused mortar cracking. Once detected, the L(0, 1) mode was sensitive to the combined effects of bond deterioration and mortar stiffness reduction. The L(0, 9) mode has negligible radial and axial displacement at the steel/mortar interface. As a result, the L(0, 9) mode is relatively insensitive to the surrounding interface conditions at high frequencies. This allows for changes in the steel cross-sectional area and bar topography to be isolated and monitored from the onset of corrosion up to severe pitting.

Longitudinal Guided Waves for Monitoring Chloride Corrosion in Reinforcing Bars in Concrete

“…Na et al [8,14,15] utilized the guided waves for the inspection of steel-concrete interfaces and glass fiber polymer-concrete interfaces. Ervin et al [16,17] used both low (<200 kHz) and high (2)(3)(4)(5)(6)(7)(8)(9) guided longitudinal modes to ultrasonically monitor the accelerated corrosion experiments. It was found that some modes were sensitive to the combined effect of bond deterioration and mortar stiffness reduction while some other modes related well to change in crosssectional area.…”

Monitoring freshly poured concrete using ultrasonic waves guided through reinforcing bars

“…The leakage depends on the relative elastic and damping properties of the surrounding concrete layer [41]. Thus, the steel-concrete interface can be characterized by ultrasonic investigations [41][42][43][44][45][46]. As concrete sets and hardens, the bond between the reinforcing bar and the surrounding concrete improves.…”

Ultrasonic guided waves for monitoring corrosion of FRP wrapped concrete structures

“…Thus, simulation of corrosion of rebars has been attempted by researchers. It has been simulated in various ways such as by introducing delamination between steel and concrete by using Poly-Vinyl Chloride (PVC) sleeves or by wrapping a soft tape on the bars [43,44]. Debonding impedes the leakage of waves into the surrounding concrete and causes increase in the signal strength at the receiving end.…”

“…It indicates increasing corrosion by loss of bond between steel and concrete. Both low and high frequency guided wave modes to monitor corrosion damage in reinforced mortar specimens have been attempted [44,45]. Corrosion has been simulated by artificially incorporating debonds and notches and has been compared with actually corroded specimens successfully [32].…”