Dynamic tensile properties of thermally treated concrete specimens subjected to varied heating rates: an investigation using the digital image correlation method

In concrete engineering, high temperatures at varying heating rates significantly affect the stability of concrete structures. In this paper, the dynamic tensile characteristics were investigated on concrete specimens subjected to heating rates ranging from 2 to 40 °C/min, using the digital image correlation (DIC) method. The results reveal a critical heating rate threshold, between 5 and 10 °C/min, which marks a shift in the influence of heating rates on both physical and dynamic tensile properties. Below this threshold, changes are minimal, but beyond it, significant effects are observed. As the heating rate increases, longitudinal wave velocity, density, and mass decrease, while porosity increases. Both wave velocity and dynamic tensile strength exhibit a linear decline with increasing heating rates, whereas porosity increases linearly. Additionally, when the heating rate surpasses the threshold, the angle between the failure surface and the loading bar increases, and the maximum principal strain in the direction perpendicular to the loading direction, measured on the specimen’s plane, decreases. Initial failure occurs at the location of highest strain, typically along the central axis of the specimen. These findings suggest that rapid heating should be avoided in concrete engineering to maintain structural integrity. However, rapid heating could be used to break and reuse concrete materials.