A Novel Structural Health Monitoring Method for Reinforced Concrete Bridge Decks Using Ultrasonic Guided Waves

Abstract

This article presents the latest improvements in a recently developed nondestructive testing (NDT) approach for early detection of various flaws (corrosion, delamination, and concrete cracking) in reinforced concrete (RC) bridge decks. The proposed method involves the use of internal steel reinforcement as a wave guide for transmitting ultrasonic waves through the system and the measurement of leaked energy from the surface of the concrete. This paper builds upon the progress made in the previously published phases of the project and aims to further explore the capabilities and practicality of the proposed NDT method. Specifically, the limits of propagation distance, effect of bidirectional reinforcement, methods of attachment and coupling of the sensors to the reinforcement and concrete, and suggestions for optimal sensor arrays are discussed in this paper based on the findings from the most recent laboratory tests and pilot field tests. The results show that with careful placement of sensors and data interpretation, early stages of localized corrosion and delamination can be detected, even when bidirectional and multiple layers of reinforcement are present. For field applications, an angled seat made of fast-setting Hydrocal gypsum cement is recommended, and it is projected that the optimal angle of attachment is 33 degrees or less from the vertical axis.

A Comparison between Ultrasonic Guided Wave Leakage and Half-Cell Potential Methods in Detection of Corrosion in Reinforced Concrete Decks

“…UGWL has the ability to identify the onset and progression of flaws in RC structures such as concrete-rebar delamination, corrosion, and cracking. The team's previous work successfully demonstrated that UGWL is capable of identifying delaminations as small as 0.2 mm (0.008 in) and the onset of rebar corrosion [1][2][3]. A study conducted by Garcia et al [2] successfully demonstrated that the amplitude of the leaked energy that radiates from the reinforcing bar waveguide is sensitive to corrosion initiation and cracks.…”

“…While a range of ultrasonic frequencies (20-100 kHz) have been used in homogeneous concrete systems, 54 kHz was found to be optimal for this application [1]. Most ultrasonic guided wave studies on RC structures have utilized lower ultrasonic frequencies [1][2][3]27,29,30], mostly because the lower frequencies have a higher sensitivity to bond conditions and are easier to solve [27]. Since the concrete is a heterogeneous material, many agree that it is better to use lower frequencies in ultrasonic testing, typically 20 to 100 kHz [27].…”

“…where A i is the amplitude of 54 kHz in the frequency domain of ith increment of corrosion and A 0 is the amplitude of 54 kHz in the frequency domain before corrosion. Further details of the development of this method and previous findings can be found in [1][2][3].…”

“…In prior work, the UGWL method, a new approach to non-destructive testing (NDT) of reinforced concrete members using ultrasound, demonstrated the ability to detect the onset of corrosion and delaminations between rebar and concrete [1][2][3]. It was demonstrated that the UGWL method can be used effectively on epoxy-coated bars and the method's field readiness was tested through two field pilot studies.…”

A 95-Year-Old Concrete Arch Bridge: From Materials Characterization to Structural Analysis

“…Concrete detector for rebar localization, depth measurement, and size estimation are necessary for the proper estimation of steel reinforcements in the existing old concrete bridge. New technologies, methods, and systems are still developed for the detection of steel rebars in concrete structures [ 61 , 62 , 63 , 64 ].…”