Developments in air-coupled contactless sensing for concrete

Recent developments in contactless, air-coupled sensing of seismic and ultrasonic waves in concrete are presented. Contactless sensing allows for rapid, efficient and consistent data collection over a large volume of material. Two inspection applications are discussed: aircoupled bridge deck scanning using seismically generated waves, and internal material reconstruction using ultrasonic tomography. The first application aims to locate and characterize shallow delamination defects within concrete bridge decks. Impact-echo is applied to defected concrete slabs using air coupled sensors. Next, efforts to apply aircoupled ultrasonic tomography to concrete are discussed. Various solutions for tomographic inversion and improvement of SNR are evaluated. Preliminary results are presented for aircoupled ultrasonic tomography to solid elements to locate internal defects. The results demonstrate that, with continued development, air-coupled ultrasonic tomography can provide improved evaluation of unseen material defects within structures.