Characterization of fracture process in concrete beams under bending using double-frequency ultrasonic wave measurements and coda wave interferometry

The paper deals with the continuous-time monitoring of fracture process of concrete under bending. A series of experiments were conducted on beams of varying dimensions. Ultrasonic wave measurements were taken throughout the mechanical degradation of the samples. The collected signals were processed using coda wave interferometry (CWI) technique with the stretching and doublet methods. Both approaches were proved to be effective in damage detection and localisation. The analysis of the results made it possible to determine the influence of sample size, sensor location, and excitation frequency on the efficiency of the applied diagnostic technique. The conclusions drawn were verified by the digital image correlation (DIC) technique, which allowed the visualisation of the actual cracks. • Coda wave interferometry can be used for efficient detection and localisation of damage in concrete • The stretching and doublet methods are effective in determining the crack location • The stretching method provides more reliable and coherent results • The accuracy of crack localisation depends on the number of sensors used • The efficiency of the CWI method is affected by sample size and the wave frequency