Nonlinear-elastic characterization of cement-based materials under uniaxial stress: A comparison between ultrasonic and resonance techniques

The nonlinear-elastic behavior of concrete and other cement-based materials has shown promising potential for determining quasistatic stresses using nondestructive testing (NDT) techniques. However, given concrete's intrinsic complex behavior, the topic is not fully understood. To investigate this problem, two groups of NDT- techniques have emerged, one based on ultrasonic wave propagation and the other one based on resonance vibration. In this research, we first present a unified theoretical description of both techniques using the 1-D classical nonlinear parameter 6G. Then, we consider a mortar specimen and characterize its material nonlinearity by measuring 6G with both techniques simultaneously. Our results show that both the torsional frequency of vibration and the S-wave speed increase, with good repeatability, as compressive stress increases. Moreover, resonance vibration yielded a 6G value almost four times greater than ultrasound, even though the theory predicts equal results. A final section discusses a possible physical explanation.

Automated summary

The nonlinear-elastic behavior of concrete and other cement-based materials has the potential for determining quasistatic stresses using nondestructive testing techniques. Two groups of NDT techniques have emerged, one based on ultrasonic wave propagation and the other based on resonance vibration. This research provides a unified theoretical description of both techniques using the 1-D classical nonlinear parameter 6G. Experimental results show that both torsional frequency of vibration and S-wave speed increase with compressive stress. Resonance vibration yields a significantly higher 6G value compared to ultrasound.