Asphalt mixture is a widely used pavement material in road and airport engineering. The incorporation of fibers has been demonstrated to substantially enhance the performance of asphalt mixtures in road applications. Nevertheless, research on the uniaxial compressive performance of fiber-reinforced asphalt mixtures and the microscopic enhancement mechanism of fibers remains limited.

The basalt fiber-reinforced asphalt mixture is selected as the research object. Material tests on basalt fiber-reinforced asphalt mixtures, including the Marshall test and uniaxial compressive tests, are conducted to study the effect of basalt fiber content on the physical and mechanical properties of asphalt mixtures, such as bulk density, stability, flow value, and compressive strength. Based on discrete element simulation, a numerical model for basalt fiber-reinforced asphalt mixture is established, in which the fibers are modeled as clumps, aggregates with diameters larger than 2.36 mm are represented as balls, and the asphalt mortar, composed of aggregates smaller than 2.36 mm and base asphalt, is simulated using a contact model. The discrete element model is verified with the test results, and the contact parameters are calibrated. An investigation is conducted into the process of crack formation, development, and failure of the asphalt mixture under uniaxial compression.

The results show that (1) with an increase in fiber content, there is a gradual decrease in bulk density and voids filled with asphalt, while the void content of the asphalt mixture, optimum asphalt binder content, and mineral aggregate voidage of the asphalt mixture increase. (2) The incorporation of basalt fibers significantly enhances the mechanical properties of asphalt mixtures, including Marshall stability, flow value, and compressive strength. In comparison with asphalt mixtures devoid of fiber, the uniaxial compressive strength increased by 13.2%, 43.3%, and 8.3% at fiber content levels of 0.2%, 0.3%, and 0.4% by weight, respectively. (3) Fiber content exerts a substantial influence on the axial compressive performance of asphalt mixtures. The maximum compressive strength value is observed at 0.3% fiber content for the asphalt mixtures examined in this study. When the basalt fiber content is below 0.6%, the compressive strength initially increases and then decreases with rising fiber content; however, it remains higher than that of mixtures devoid of fiber. In contrast, when the fiber content exceeds 0.6%, the compressive strength decreases below that of mixtures devoid of fibers. (4) The discrete element model of basalt fiber-reinforced asphalt mixtures accurately simulates the uniaxial compression process.

Microstructural analysis reveals that increasing basalt fiber content significantly reduces edge fragmentation and crack propagation in asphalt mixture specimens, while the number of interparticle contacts increases markedly. Analysis indicates that the discrete element model of asphalt mixtures developed using discrete element modeling software can accurately simulate the internal microscopic mechanisms during uniaxial compression, revealing the influence of basalt fibers on contact evolution and crack propagation within the mixture. The addition of an appropriate amount of basalt fibers enhances the physical and mechanical properties of asphalt mixtures. However, excessive fiber content may lead to fiber aggregation phenomena, resulting in performance degradation. Therefore, for practical engineering applications, the optimal fiber dosage should be determined through experimental testing and theoretical analysis based on specific conditions. The findings of this study have significant reference value for the design of fiber–asphalt mixture pavements and airport runways.