Characterization of discontinuities inside massive concrete structures with normal dc resistivity logging

Abstract

Normal electrical resistivity logging was used to investigate the internal concrete structure. This study proposed an approach, presented by series of steps, to detect and characterize the conductive discontinuities. First is modeling, a database of electrical responses of discontinuities with an aperture range (0.005m–0.030m), resistivity contrast (5–40) and extension (0.05m–20m) was created. Second is the use of incremental analysis, employed on the created database, to obtain a first estimation of discontinuity parameters. However, the result is not yet sufficient in terms of dimension and activity. This led to the third step, the optimization method. In this last step simulated annealing was chosen to improve the results. This allowed reducing the possibilities of finding solutions to 2 or 3. In order to validate the proposed approach, application on numerical and experimental data was realized. Results show that normal electrical resistivity logging can detect and locate the conductive discontinuities. From the proposed approach, these conductive discontinuities can be characterized as ideal (i.e. without contact zone) and isolated. The ability to identify relevant parameters and provide discontinuity characteristics could eventually serve as basis for civil engineers in making efficient decisions regarding concerns on concrete structure.