Fracture toughness of basalt fiber-reinforced hot recycled asphalt mixtures: a study based on DIC technology

ABSTRACT In cold regions, hot recycled asphalt mixtures often suffer from low-temperature cracking. Basalt fiber, a widely recognized toughening material, offers promising potential to mitigate this issue. This study employs digital image correlation to monitor the fracture evolution during semi-circular bending tests, focusing on the reinforcing effect of basalt fibers and analyzing their contribution to improving the low-temperature fracture resistance of RHMA under different RAP contents. Fracture energy, fracture toughness, and crack tortuosity were utilized as key indicators of crack resistance. The correlations between crack tortuosity and both fracture energy and fracture toughness were analyzed, while strain fields and horizontal displacements at observation points were analyzed to characterize the cracking process. The results demonstrate that the incorporation of basalt fibers enhances fracture energy by 23%–39% and improves fracture toughness by 10%–21%. Moreover, basalt fibers significantly altered the crack propagation path, increasing crack tortuosity by 8.2%–12.8%. An increase in RAP content intensified the stress concentration on both sides of the crack, leading to pronounced local strain accumulation at the crack tip. The presence of basalt fibers effectively reduced strain concentration near the crack tip, dispersed high-strain zones, and delayed crack propagation, thereby enhancing the overall fracture resistance of the mixture.