Surface wave dispersion in large concrete structures

The present paper discusses the repair characterization of large concrete surfaces based on the propagation of low-frequency elastic waves. A common repair method is cement injection. As a result, cracks and voids are eliminated increasing the measured average pulse velocity by about 5%. However, the central frequency of the pulses exhibits higher sensitivity to the repair increasing by about 15%. Additionally, the velocity of longitudinal waves exhibits a dependence on frequency. This dispersion is eliminated after repair being an indication of the repair efficiency, while Rayleigh waves are only slightly dispersive due to their long wavelength which enables them to travel below the shallow defects.