Identification of incipient pitting corrosion in reinforced concrete structures using guided waves and piezoelectric wafer transducers

Abstract

Corrosion poses a great threat to ageing civil infrastructure in the world, and researchers are seeking methods to monitor the corrosion in reinforced concrete structures. Detection of corrosion at its incipient stage has been an impending task in the non-destructive testing of materials. Several non-destructive testing methods to assess the presence of corrosion exist. The limitation of the current methods is that either they require measurement at several points or they require a large network of sensors. Guided wave-based monitoring overcomes these limitations because a large area can be scanned using fewer sensors. The process of corrosion is complex, and it leads to a simultaneous reduction in the diameter and the debonding between concrete and reinforcing steel bars in reinforced concrete structures. However, some of the recent studies that explore the use of guided waves focus only on the detection of the individual effect of diameter reduction and debonding of the rebars in reinforced concrete by artificially inducing the damage. In this study, an accelerated corrosion setup is deployed to induce pitting corrosion in reinforced concrete beams using the impressed current method. These beams are continuously monitored using ultrasonic guided waves that are generated and received by piezoelectric wafer transducers that are attached to the rebars. It is shown that the incipient stage of pitting corrosion can be detected successfully, and the mechanism of corrosion process, which involves the corrosion initiation, progression, and diameter reduction-and-cracking phases, can be established from the signal characteristics of the longitudinal and flexural-guided wave modes. The impressed current flow in the corrosion cell also confirms the various phases of corrosion.

Smart Cathodic Protection System for Real-Time Quantitative Assessment of Corrosion of Sacrificial Anode Based on Electro-Mechanical Impedance (EMI)

“…Lead zirconate Titanate (PZT) transducers find a variety of applications in structural health monitoring such as assessing performance and state of pre-stressed concrete [9], [10], damage localization and monitoring [11]- [14], monitoring debonding in composite structures [15]- [17], monitoring of fatigue damage and curing of adhesives [18], [19] etc. More recently, PZT transducers embedded within infrastructure are employed as smart sensors for real-time monitoring [20], [21] for applications such as impact monitoring [22] and detection of internal damage in concrete and embedded reinforcements [23], [24]. While PZT transducers have also been employed for corrosion monitoring [25], [26], an analytical and quantitative correlation of change in impedance of the PZT transducer due to the corrosion of the system under inspection requires further development.…”

The use of ultrasonic guided waves for the inspection of square tube structures: Dispersion analysis and numerical and experimental studies

“…Ultrasonic guided wave technique 4–10 has recently emerged as a high efficient testing method for large-scale structures. It shows great potentials in NDE and SHM for inspecting structures of many fields, that is, plates, 11–16 pipelines, 17–20 railways, 21,22 and steel strands.…”

Guided Wave Inspection of Bars in Reinforced-Concrete Beams Using Surface-Mounted Vibration Sensors

“…Where the rebar is embedded in concrete this is enabled in a laboratory setting by leaving the ends exposed, but in practical applications transducers must be embedded in the composite beam during construction. One commonly advocated approach to detecting corrosion has been to measure the strength of longitudinal [4,5] and/or flexural [6] wave transmission along a rebar. A significant limitation is that the signal strength may either increase or reduce with corrosion.…”