Using “Focusing to a Point” Algorithm for Reference-Free Measurement of the Speed of Ultrasound in Tomography of Concrete Engineering Structures

Abstract

It was noted that in most ultrasonic tomographs for concrete products, tomograms are constructed based on the velocity of body (longitudinal, transverse) ultrasonic waves, calculated from the easily measured velocity of surface waves. However, in engineering structures exposed to climatic or other impacts, the state of the concrete structure can vary greatly from its surface to its depth, leading to errors in determining the body ultrasound velocity and, consequently, to inaccuracies in displaying defects in the structure and product dimensions. In order to improve defect location accuracy, a new reference-free method has been proposed for measuring the speed of ultrasound in the volume of large-sized engineering structures. The method employs ultrasonic antenna arrays that take advantage of the “focusing to a point” algorithm when constructing tomograms, provided that a point reflector (e.g., an access hole) is present in the product.