Concrete cover characterisation using dynamic acousto-elastic testing and Rayleigh waves

•Dynamic acousto-elastic testing by using Rayleigh waves as probe wave and the first bending mode excitation as pump wave.•Nonlinear dynamic acousto-elastic behaviour of concrete.•High relative variation of nonlinear parameters for assessment of thermally damage concrete and carbonated concrete.•The method opens up new possibilities for in situ measurement.

This paper presents the application of surface Rayleigh waves in nonlinear dynamic acousto-elastic testing for the nondestructive evaluation of the concrete cover. Numerous physical phenomena, such as conditioning and slow dynamics, characterising the dynamic non-classical nonlinear elastic behaviour of many types of micro-heterogeneous solids, were observed in concrete. Rayleigh waves were used as probing waves to evaluate the effect of local property changes in a concrete cover. The proposed method was validated for two typical problems of concrete durability, in a case of thermal damage – distributed micro-damage – and in a case of carbonation – surface problem with determination of the carbonation depth. In both cases, the results showed that the relative variation as a function of material changes of the nonlinear parameters was much higher than that of the ultrasonic pulse velocity.