Investigation on Fatigue Damage Characteristics of Basalt Fiber-Reinforced Asphalt Mixtures with High RAP Content

High-RAP asphalt mixtures are highly susceptible to fatigue brittle fracture. This study investigated the fatigue damage evolution of basalt fiber (BF)-reinforced high-RAP mixtures. Four-point bending fatigue tests were performed to evaluate the stiffness damage factor and the ratio of cumulative dissipated energy change RCEDC. The ExpDec2 model and a second-derivative criterion were utilized to quantify steady-state energy dissipation and partition damage stages. Results indicate that BF extended fatigue life, yielding a 55% improvement at 70% RAP content. Model evaluations revealed that in the initial stage, increasing RAP delayed the critical damage inflection point due to accelerated non-steady damage, whereas BF shifted inflection points forward by constraining early damage accumulation. In the stable propagation stage, BF reduced the energy dissipation rates of 50% and 70% RAP mixtures by 44% and 22%, respectively. These quantitative results provide essential performance data regarding the effect of BF on the fatigue life and energy dissipation of high-RAP mixtures, serving as a practical reference for the design and durability optimization of sustainable asphalt pavements.