SGER: Ultrasonic Imaging for Concrete Structural Elements

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Visual images that describe the location, size and shape of embedded defects provide directinformation about the condition of a structure. Many individual data are needed to construct aneffective image however, and the inherent large size of concrete structures results in an enormousamount of data needed to construct an adequate image. One approach to empower the applicationof ultrasound for such imaging is to eliminate the need for physical contact between the sensorand tested structure. The PI has recently completed research on air-coupled ultrasonic testing forconcrete. The research findings illustrate that ultrasonic waves traveling through concrete can bedetected with a fully contact-free configuration using air-coupled sensors. In this project, theefficacy of air-coupled ultrasonic tomographic imaging will be investigated. The methods will first beevaluated experimentally using reduced-scale (fifth-scale) concrete column samples. Bothrectangular and circular cross-sectioned column samples will be considered for each scanconfiguration. Some concrete samples will contain embedded artificial volumetric (void) andplanar (crack) defects. Other defect-free specimens will be subjected to simulated seismic loads,using the fifth-scale test facility at the University of Illinois. Application to full-scale concretecolumns, which are currently being tested as part of a NEES small group project at the Universityof Illinois, will then follow; the columns will be non-destructively imaged before and after themechanical (seismic) loading is applied as part of the NEES project. Successful completion of the work will enable unparalleled internaldefect characterization for concrete structures. At the same time, the effort provides a uniqueopportunity to extend development of an emerging technology that is currently being developedby the PI: air-coupled sensing for concrete structures.