Evaluation of high-content warm-mixed rubber modified asphalt: experimental investigation and molecular dynamics simulation

This study investigates the effects of crumb rubber (CR) content and the activation treatment of CR with aromatic oil and rosin oil on the performance of warm-mixed crumb rubber modified asphalt (WRMA) through laboratory tests and molecular dynamics (MD) simulations. The workability of WRMA decreases notably when CR content exceeds 30%, with optimal high-temperature performance observed at 30% CR but poorer performance at 40%. Additionally, activation of CR with aromatic oil enhances asphalt’s high-temperature performance. Fourier Transform infrared spectroscopy (FTIR) analyses reveal no introduction of new functional groups during CR activation with aromatic and rosin oils, indicating a physically mixed state with asphalt. Increasing CR content reduces WRMA surface roughness by inhibiting the formation of bee-like structures, associated with smaller structure sizes. Moreover, aromatic and rosin oils promote the proximity of aromatic molecules to rubber, impacting asphaltene and resin aggregation. Sasobit demonstrates high mobility, while rosin oil exhibits a distinct peak. Furthermore, diffusion coefficients highlight Sasobit and light component mobility, peaking at 25% CR content for CR and warm-mix agents. However, the addition of aromatic and rosin oils significantly reduces mobility, particularly for rubber molecules. Finally, CR content minimally affects WRMA’s solubility parameters until reaching 40%, where a 2.2% decrease indicates reduced CR-asphalt compatibility.