Application of Plane Wave Imaging and Processing for Measurement of Reflectors in Concrete

Measurement and quantification of detected subsurface features is an important step toward the evaluation of concrete structures. A model-based evaluation relies on better spatial measurement and updating of internal features, apart from detection. In this work, we aim for precise measurement and tracing in the spatial domain of features like internal multilinear crack patterns and embedded circular and polygonal ducts, with the data from a limited angle of view of one-sided inspection on concrete. Plane wave imaging (PWI)—which is rather completely new in concrete—is used for subsurface image reconstruction, due to which better and more feasible tracing has been achieved, compared to images of the total focusing method (TFM). The dependence of measurements on scanning frequency has been removed with image segmentation and morphological erosion in the reconstructed images. With one-sided inspection of general features, the part facing the inspection surface has been traced with considerable accuracy, but for circular embedments, the complete spatial trace is marked after ensuring that it is indeed a circular object. The estimation errors in both the spatial location of the center and the radius measurement of circular features have been found to be under the 5% limit. For multilinear cracks, the error in measurement of the length of crack segments is within 4%.