Measuring Rebar Cover Depth in Rigid Pavements with Ground-Penetrating Radar (05-2467) - MP-17
Imad L. Al-Qadi, University of Illinois, Urbana-Champaign
Samer Lahouar, Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Tunisia
Kun Jiang, University of Illinois, Urbana-Champaign

Ground penetrating radar (GPR) is a nondestructive investigation tool that is usually used in flexible pavement evaluation to estimate the thicknesses of the different layers composing the pavement. Ground penetrating radar is also used in flexible pavements to detect subsurface distresses, such as moisture accumulation and air-voids. For rigid pavements and bridge decks, GPR is used to measure the thickness of the concrete slab and to detect the location of reinforcing bars (rebar). Rebar detection is typically achieved, in this case, when an experienced operator finds the rebar’s classic parabolic signature in the GPR data. This paper presents image-processing techniques that can be used to automatically detect the rebar parabolic signature in GPR data collected from rigid pavements using a high-frequency ground-coupled antenna. After rebar detection, the reflected parabolic shape is fitted to a theoretical reflection model to estimate the pavement’s dielectric constant and the rebar depth. The developed algorithms were validated on GPR data collected from a known continuously reinforced concrete pavement (CRCP) section. The presented technique showed an average error of 2.6% on the estimated rebar cover-depth.