Assessment of wave modulus of elasticity of concrete with surface-bonded piezoelectric transducers

Abstract

Measurement of the modulus of elasticity of concrete based on wave propagation technique is a critical method to assess condition and performance of concrete materials and structures. In this study, a combined numerical and experimental study is conducted for assessment of wave modulus of elasticity (WMoE) of the fully-cured concrete using surface-bonded PZT (lead zirconate titanate) transducers, also so called smart piezoelectric modules (SPMs). Rayleigh wave (R-wave) acquired from the surface-bonded PZT transducers is selected as the main target signal, and the explicit physical relationship between R-wave and WMoE is applied in signal processing. Piezoelectric solid element and electric load are applied to model the PZT transducers and actuate stress waves in numerical simulation, respectively. The numerical analysis provides a better understanding of surface wave propagation in concrete and sheds light on physical experiment. Effects of excitation frequency, excitation waveform, and size of PZT transducers are first examined in numerical simulation and then validated by physical experiment. Good agreements between the numerical and experimental results show that the Hanning windowed 5-peak or 7-peak sinusoidal tone burst at the frequency range of 40 kHz to 100 kHz is recommended as the excitation signals; while the width-to-thickness ratio of square transducers ranging from 10 to 15 is suggested for selection and design of surface-bonded PZT transducers. Effective measurement of WMoE using the surface-bonded PZT transducers shows great potential for nondestructive evaluation of concrete, and it can be used for condition assessment and health monitoring of concrete structures.