Imaging of internal cracks in concrete structures using the surface rendering technique

The impact echo method is effective in the inspection of concrete defects. If the test area is large and many tests are performed, it is difficult to get a picture of the concrete interior by examining a series of test spectra. In order to provide the engineers with a more direct way of detecting the defects in the structure, this study proposes a three-dimensional (3D) imaging method to depict the internal cracks in concrete structures. To acquire the test data, a mesh is drawn on the surface of the concrete. Then, impact echo tests are performed at the grids. The recorded signals are processed to obtain the depth spectra of the concrete. Finally, the surface rendering technique is adopted to construct the 3D image of the concrete interior. Both numerical simulations and model tests are used to verify the proposed imaging method. It is seen that surface rendering technique can be used to show the internal cracks in the concrete specimens successfully.