The decision to remove and replace faulty concrete can be a costly one. It is important that defects be as clearly identified and located as possible so that only concrete warranting replacement is removed. One method growing in use to accomplish that purpose is pulse-echo non-destructive testing (NDT). Pulse-echo tests in concrete disclose the presence and location of discontinuities in the concrete, such as cracks, voids, honeycomb, sawdust, metal plates, and lack of consolidation around rebars.
Because no concrete structure is totally free of imperfections, it is vital to distinguish between the relatively minor defects and those which may threaten the structural integrity of a member. The pulse-echo test can determine the extent and location of internal discontinuities so that a realistic analysis of internal defects can be made.
With pulse-echo testing a number of things can be learned about the soundness of concrete. Among them are the compressive strength, degree and uniformity of consolidation, location and orientation of cracks or cold joints, presence of unconsolidated material around rebars, improper bonding of epoxy injection repairs, thickness of slabs on ground, presence of concrete that has frozen early, and sizes of voids under slabs on ground.