1. Scope

Keywords

Rationale

Ultrasonic stress waves are used to assess uniformity of concrete structures by following standards like C597 - Standard Test Method for Ultrasonic Pulse Velocity Through Concrete. However, C597 requires two-sided access on a structure, which is not always possible. Ultrasonic pulse velocity is unable to assess the depth or detailed extent of discontinuities. Another ultrasonic stress wave test is impact echo (C1383 - Standard Test Method for Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method) which is a one-sided test that can locate discontinuities and can be used to assess uniformity. This test can find depth of defects but still has a lack of resolution on the extent. Impact echo is also limited by structure geometry and has a complex analysis with time domain and frequency domain wave forms. Neither of these tests can effectively distinguish the nature of the reflected object, e.g. metallic or non-metallic. The ultrasonic pulse echo test can assess uniformity and image discontinuities from a single side with fewer geometry restrictions. This method produces a tomography image that allows for easier interpretations with a precise determination of both depth and extent. Furthermore, polarity of the a-scan waveform can be used to discern between metallic (rebar, PT ducts) and non-metallic (delaminations, cracks, honeycombing) reflections. Devices have been publicly available and manufactured since about 2010 and have since become popular in durability testing and forensic evaluation. Independent software is emerging to customize raw data analysis. A standard practice is necessary for this method to establish commonality between users conducting ultrasonic pulse echo tests.