Characterizing the Interaction Between Asphalt and Mineral Fillers in Hot Mix Asphalt Mixtures: A Micromechanical Approach

Asphalt mastic serves as a critical binding material in hot mix asphalt mixtures, significantly influencing the performance and durability of asphalt pavements. The interaction between asphalt and mineral fillers directly affects the binding properties of the mastic. In this study, the adsorbed asphalt film thickness was used as an indicator to evaluate the interaction between asphalt and mineral fillers. A micromechanical approach was proposed to calculate this thickness, and the results were compared using the Hashin model, the Mori–Tanaka model, and the generalized self-consistent model. The results demonstrate that the adsorbed asphalt film thickness, as determined using the micromechanical approach, ranged from 0.01 to 0.37 µm. The Hashin model was found to provide the most accurate characterization of the interaction between the asphalt and the mineral fillers. The order of adsorbed asphalt film thickness was as follows: coal gangue asphalt mastic > limestone asphalt mastic > fly ash asphalt mastic. Higher concentrations of acidic SiO2 in the mineral fillers resulted in a weaker interaction between the asphalt and the fillers. When the temperature was below the softening point of the asphalt, the interaction strength decreased as frequency increased. Conversely, when the temperature exceeded the softening point, the interaction strength increased with frequency. The effect of temperature on the interaction capability was further influenced by the characteristics of the mineral fillers. The micromechanical-based method proposed in this study eliminates the dependency of the evaluation indicator on the volume fraction of mineral fillers, thereby providing a more accurate characterization of the interaction between asphalt and fillers. This approach provides a theoretical foundation to guide the design of asphalt mixtures.