Identifying the onset, type, and location of deterioration in reinforced concrete using ultrasonic testing

In an embedded guided wave system, energy gets leaked out into the embedding material as bulk waves. This is referred to as leakage. This dissertation examines the possibility of using the leakage of an embedded ultrasonic guided wave system to identify the type, onset, and location of delamination in reinforced concrete. The study is motivated by the deteriorating infrastructure of the U.S. and proposes a structural health-monitoring tool for reinforced concrete bridge decks. The ultrasonic testing (UT) method proposed consists of a cylindrical waveguide (steel rebar) embedded in another material (concrete) in order to determine the onset of changes in the condition of the steel rebar and steel rebar-concrete interface. During the experimental work, it was observed that the ultrasonic guided wave leakage (UGWL) can successfully identify the onset of delamination with widths less than 0.008 inches. This study also demonstrated that the amplitude of the leaked waves radiating from the steel bar waveguide is sensitive to rust (onset of corrosion) and cracks independent from the steel and concrete interface. Velocity measurements can also be used to identify the development of these delamination and cracks; however, its sensitivity is less than that of amplitude measurements. In addition to being sensitive to the onset of the aforementioned deterioration, UGWL demonstrated an ability to estimate the location of both the onset of delamination and corrosion. The study showed that the influence that delamination and corrosion have on amplitude readings monitored by arrays of sensors opposes one another, and results suggest that it is possible to identify the onset and location of both these types of deteriorations simultaneously. The method utilizes amplitude measurements and demonstrates the potential to examine larger areas compared to most other non-destructive testing (NDT) methods used for bridge decks