Temperature-dependent longitudinal-wave acoustoelastic behavior of concrete

The acoustoelastic effect provides a physically grounded basis for evaluating internal stress in structures, but temperature variation can substantially interfere with acoustoelastic stress evaluation in concrete. Nevertheless, the influence of temperature on the acoustoelastic response itself remains insufficiently understood. This study investigates the temperature dependence of the longitudinal-wave acoustoelastic behavior of concrete over the range of 10–50 °C through two complementary experimental schemes: variable-temperature tests on the same specimens and constant-temperature tests on independent specimens. The results show that the unstressed-state longitudinal wave velocity decreases approximately linearly with increasing temperature, while the acoustoelastic coefficient increases correspondingly, indicating enhanced stress sensitivity of ultrasonic wave propagation at higher temperatures. For the same specimen, both effects are largely reversible during heating and cooling. Across different specimens, although the inherent heterogeneity of concrete leads to noticeable scatter, the same temperature-dependent trend remains statistically identifiable. These findings demonstrate that temperature affects not only the unstressed-state wave velocity but also the acoustoelastic response, highlighting the necessity of temperature compensation in acoustoelastic stress evaluation of concrete. More broadly, this study also indicates that a complete understanding of concrete acoustoelasticity and its application to structural stress inversion still require further investigation.