Acoustic Tomographic Imaging of Concrete Infrastructure

Acoustic tomography is an established nondestructive evaluation (NDE) technology that can be used to image the interior of large grained building materials such as concrete or masonry. A literature search focusing on geotomography and tomographic applications in infrastructure NDE was performed. This paper highlights some historical publications of interest as well as illustrates the general theory of acoustic tomography. A questionnaire was sent to the transportation departments of the 50 states. The questionnaire is general in scope, written to ascertain which NDE methods the states are using, and to identify their concerns and interests. The questionnaire asks the state officials whether the tomography technique seemed useful—the results of this question are presented in this paper. A data acquisition and processing system has been developed to facilitate an acoustic tomography system. Using an array of transducers and data processing software, the system is fast enough to internally image concrete structures in the field. Laboratory results and field applications are presented in the form of three case studies. The technique is shown to be useful for imaging of cracks, cold joints, and voids in concrete structures.