Two different kind of waves have been utilized in the wave-based NDT method of concrete, they are elastic waves (or called stress waves) and electromagnetic waves. The wave-based NDT methods have been successfully applied either to the estimation of concrete strength or the evaluation of concrete structure integrity. Furthermore, recent advancements of the wave related research also showed the great potential of using waves to solve more important problems in the NDT of concrete structures.

In this paper, a brief description of the existing NDT methods for testing concrete structures is given first, then, the general research direction on the development of wave-based NDT techniques of concrete structures is followed. Secondly, the basic principles and applications of several wave-based NDT techniques of concrete structures will be described. The methods include the ground penetrating radar (GPR) that is based on the electromagnetic wave propagation and five elastic wave based NDT methods. The elastic wave methods include ultrasonic wave, impact-echo, spectral analysis of surface wave (SASW), skimming longitudinal and Rayleigh waves (SLR), inverse and phase detection methods. The acoustic emission method in the safety monitoring of concrete structure will also be addressed.