“…From a broad viewpoint, nondestructive methods developed for the evaluation of the damage condition of concrete to date include visual and optical inspections and stress-wave based methods, as well as nuclear, magnetic, and electronic methods [ 3 ]. Of these methods, ultrasonic techniques involve measurements of pulse velocity [ 9 , 10 , 11 ], characteristics of guided waves [ 12 ], surface-wave transmission [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], acoustic emission [ 5 ], diffuse ultrasound [ 25 , 26 , 27 , 28 ], coda wave interferometry [ 28 , 29 ], and nonlinear ultrasound [ 30 , 31 ]. Each of the ultrasonic techniques makes use of different characteristics of ultrasound to detect the location and propagation of cracks, to estimate the width and/or depth of cracks, or to evaluate the durability and residual mechanical properties of concrete [ 32 ].…”