Hydrophobic gradient design of modified asphalt and its influence on pavement performance

This study investigates the influence of asphalt hydrophobicity on pavement performance by incorporating different hydrophobic materials into asphalt and establishing a hydrophobic gradient. Molecular dynamics simulations were conducted to verify material compatibility and elucidate interfacial interactions. The rheological and low-temperature properties of hydrophobic modified asphalt were evaluated using DSR, MSCR, and BBR tests, while storage stability was assessed through a separation test. Results showed attractive interactions between hydrophobic materials and asphalt and repulsive interactions between modified asphalt and water, enhancing interfacial stability and hydrophobicity. Compared with base asphalt, the hydrophobic-modified asphalt exhibited a more than 50% increase in G*/sinδ, an over 60% decrease in Jnr, and a threefold increase in R, indicating improved resistance to high-temperature deformation. BBR stiffness decreased by 50% and the m-value increased by 30%, demonstrating enhanced low-temperature cracking resistance. All separation-temperature differences remained below 2.5℃, meeting engineering requirements. Rutting resistance and water stability initially improved and then declined with increasing hydrophobicity, with maximum increases of 25% and 5%, respectively. The permeability coefficient decreased by 70%, while skid resistance remained largely unchanged. Wet skid resistance improved, with its decay rate decreasing from 16% to 5.7%. The optimal contact angle range was determined to be 110–130°.