Imaging reinforced concrete: A comparative study of Ground Penetration Radar and Rebarscope

Geophysical techniques have been playing a very vital role in subsurface imaging in the recent past. Technology has been making it both reliable and convenient to utilize non-destructive geophysics techniques like Ground Penetration Radar, Induction current based Rebarscope, Seismic methods, ERT, etc. The applications range from shallow subsurface investigation of Bridge decks to old tunnels, mapping of rabars in a pre-existing construction and analyzing the concrete strength. The thesis constitutes of a comparative study and analysis of a Ground Penetration Radar system and a Rebarscope. Individual parameters obtained directly from the study and obtained indirectly from the study shall be analyzed for a better quantitative understanding of their variation and errors to optimize the utility of the instruments individually. Data obtained from both Ground Penetration Radar system and Rebarscope would be compared for accuracy in determining the rebar depth. For the experiments, pre-designed concrete slabs are constructed with rebars at various depths and defects in concrete. Furthermore, a combination of both the instruments is used to minimize errors and to achieve better control over the intrinsic and extrinsic errors of the instruments to undertake real world studies with better dependency. A calibration, comparative and combination study of Ground Penetration Radar and Rebarscope is important for the very purpose of better understanding of the quality of concrete, especially in its initial stages of degradation. The amplitude variation in the signal and dielectric permittivity of the concrete indicates concrete quality. The study illustrate the superiority of the Ground Penetration Radar system, but in cases of highly varying degradation and construction errors Rebarscope plays key role in accurate depth estimation of the reinforcement rebars. The study highlights some limitations of GPR surveys and proceeds to address the limitations by utilizing a Rebarscope in combination with GPR system --Abstract, page iii