Behavioural study of surface Rayleigh waves in concrete structure containing delamination

Abstract

Delamination is one of the defects that cause concrete structures to fail in structural integrity. For this reason, the assessment of concrete delamination without affecting the serviceability and functionality of concrete structure is essential. Non-destructive tests (NDT) are developed and applied to serve this purpose without damaging the structure components. In this study, Rayleigh wave (R-wave) is proposed to determine the extent of delamination in concrete. Numerical simulations were carried out to examine the behaviour of R-waves propagated through the concrete medium with different concrete delamination conditions, i.e., top delamination and bottom delamination. The relationships between the changes of R-wave group velocity and peak frequency with the existence of delamination were established. The established data were then verified with experimental measurements. It is found that the R-wave group velocity is reduced in the presence of delamination. Furthermore, the group velocity of R-wave is relatively faster while propagating through the delamination layer which is closer to the testing surface. In addition, the peak frequency retrieved from R-wave power spectrum also reduced in the presence of delamination. Owing to these observed changes, the potential of utilising R-wave group velocity and peak frequency in the assessment of concrete delamination is high.