Research on the Reinforcement Mechanism of Fiber–Asphalt Interface Based on Molecular Dynamics

Adding fibers to asphalt mixtures is an effective approach to ensure that asphalt pavements exhibit excellent low-temperature crack resistance and high-temperature stability during service. To investigate the reinforcement mechanism of the fiber–asphalt interface, molecular dynamics simulation was employed to establish four types of fiber models and their corresponding interface models with asphalt. The cohesion formation mechanism of the fiber–asphalt interface was revealed from three aspects: adhesion, aggregation, and diffusion. The key findings obtained are as follows: Among the four components of asphalt, aromatics and resins are the primary contributors to the nonbonded interaction energy at the asphalt–aggregate interface. Differences in the chemical composition of the fiber surface exert a decisive influence on the adhesion of the asphalt–fiber interface system. The diffusion of small saturated molecules is significantly affected by volume fraction, while the diffusion of large styrene–butadiene–styrene block copolymer (SBS) and polyolefin elastomer (PTW) molecules mainly depends on interaction energy. After surface modification of SiO2, the strong adsorption of asphalt molecules intensifies the aggregation degree of asphalt molecules, rendering the asphalt molecular structure system more stable and dense.