Imaging Concrete Structures Using Air-Coupled Impact-Echo

Abstract

In this paper, air-coupled impact-echo is successfully applied for nondestructive evaluation of concrete. The air-coupled sensor is a small ( 6.3 mm diameter) measurement microphone located several centimeters above the top surface of the concrete being evaluated. Unwanted ambient acoustic noise is attenuated by a specially designed sound insulation enclosure. Test results show that air-coupled sensors are effective for impact-echo when appropriate impactors are used. Impact-echo data obtained by air-coupled sensors are equivalent to those obtained by conventional contact sensors. Test results from concrete slabs containing artificial delaminations and voids are reported, where an air-coupled impact-echo scan is conducted over the entire slab area. Defects are located in the generated two-dimensional contour image. The areal size of defects are accurately determined when the measurement point spacing in the scan is smaller than half of the expected defect size. Test results from air-coupled impact-echo sc...