Evaluating the fracture characterization of asphalt mixtures under freeze-thaw damage based on full-field measurements

Understanding the fracture characterization of asphalt mixtures is important to improve pavement performance in seasonal frozen regions. It is necessary to analyze the cracking characteristics and mechanism of asphalt mixtures under the action of freeze–thaw damage. The semi-circular bending (SCB) crack test combined with digital image correlation (DIC) was conducted to evaluate the fracture characterization of asphalt mixtures under freeze–thaw cycles. The X-ray scanning measurement, bending beam rheology (BBR) test, oblique shear test, the generalized Maxwell model (GM), and the cohesive zone model (CZM) were utilized to reconstruct the 3D heterogeneous finite element (FE) model and reveal the damage mechanism. The results indicated that the freeze–thaw cycles negatively affected the cracking resistance of asphalt mixtures. After 20 freeze–thaw cycles, the fracture energy, stiffness, flexibility index, stress intensity factor, and crack evolution rate decreased by 22.96%, 19.53%, 63.93%, 63.93%, and 61.15%, respectively. The FE model was able to reflect the mechanical properties of asphalt mixtures with different numbers of freeze–thaw cycles well. The FE model can well reflect the mechanical properties of asphalt mixtures under different numbers of freeze–thaw cycles. It also reveals the deterioration of asphalt mortar properties and interfacial adhesion under the action of freeze–thaw damage, which leads to the reduction of internal stress transfer efficiency and attenuation of cracking resistance of asphalt mixtures. This study contributed to the damage mechanism evaluation of asphalt mixtures in seasonal frozen regions and may help with pavement design, construction, and maintenance.