Prototype System for Implementing the Ultrasonic Guided Wave Method on the Field

Until recently, there were no methods for structural health monitoring of new reinforced concrete bridge decks, or diagnosis of existing ones, with the sensitivity to detect the early onset of various types of deterioration. Past and current Nebraska Department of Transportation (NDOT) - UNL collaboration on this topic by the research team has developed a novel technique and succeeded in answering this gap. This method involves leakage of ultrasonic guided waves (UGW). In this method, the waves leaked from the wave guide (steel rebar) are detected by an array of receivers (R) placed on the surface of the concrete. Based on the location of the R, the increase or decrease in the amplitude of the detected waves, if read in the frequency domain, can be compared to theoretical expectations and a prediction can be made on the type, size, and location of one of the following flaws: corrosion, delamination, and cracking in concrete independent of rebars. While these accomplishments are exciting, they have all taken place in the controlled environment of a laboratory. By leaving the end of the rebar exposed, the attachment of the transmitter to the rebar has not been an issue, it was accomplished by simple grease-coupling. Also, by avoiding interference from the environment, signals have been clear and repeatable; and no issues were observed with damage to the equipment over time. As such, the next step is to make this method more practical by developing ways to overcome issues that will occur on the field. The ultimate goal of this project is to make the previously developed innovative testing method, namely the use of the leaked ultrasonic guided waves for the early detection of multiple flaws in reinforced concrete bridge decks, more practical and field-application ready.