Short mineral fibers can modify load transfer across several asphalt damage modes, but direct comparisons within one controlled mixture matrix remain limited. This study compared 6 mm basalt fiber (BF) and glass fiber (GF), incorporated by the dry process at 0.2%, 0.3%, and 0.4% of the total mixture mass, in dense-graded hot-mix asphalt prepared with a 60/70 penetration-grade binder at a fixed asphalt content of 5.0% by total mixture mass. Marshall response along with dry and moisture-conditioned indirect tensile strength was first used to examine dose dependence and select a common dosage for further testing. The 0.3% mixtures were then evaluated by wheel tracking at 60 °C, constant-strain four-point bending fatigue, and an adapted Cantabro abrasion procedure before and after thermal aging. Both fibers produced a non-monotonic load-capacity response, and 0.3% was selected for the extended test program based on the combined Marshall and tensile response within the evaluated dosage range. At this dosage, BF and GF increased Marshall stability by 27.2% and 17.5%, increased dry tensile strength by 15.5% and 11.9%, and reduced rut depth after 10,000 wheel passes by 30.0% and 22.9%, respectively. Fatigue life increased by 49.1% and 46.3%. After seven days of aging at 60 °C, Cantabro mass loss decreased from 27.0% for the control to 15.1% for BF and 18.3% for GF. Across the evaluated laboratory response modes, BF showed larger numerical improvements in several indicators, particularly rut depth and aged particle loss.
