Multiscale interactions in graphene modified asphalt

The influence of graphene on asphalt performance and its underlying multiscale modification mechanisms remains insufficiently understood. This study combined morphological, thermal, and rheological tests with molecular dynamics simulations and quantum mechanical (QM) calculations to investigate graphene modified asphalt. The results show that graphene was relatively uniformly dispersed at 1.0–1.5 wt%, whereas noticeable aggregation and structural heterogeneity appeared above 2.0–2.5 wt%. At 3.0 wt%, the glass-transition temperature shifted downward by 6.07 °C, while the heat-capacity change ( ΔCp ) decreased by 37.37 %, and the thermal conductivity (TC) increased from 0.161 to 0.272 W/(m·K). Graphene increased complex shear modulus ( G* ) and rutting factor ( G*/ sin δ ) and reduced the phase angle ( δ ), indicating enhanced stiffness and elasticity under small-strain loading. However, increased J nr and J nr-diff revealed greater residual deformation and stress sensitivity under repeated creep loading, particularly at higher dosages. Nonequilibrium molecular dynamics (NEMD) and reverse nonequilibrium molecular dynamics (RNEMD) simulations reproduced the experimental trends and further revealed that the thermal-conductivity enhancement was associated with strengthened interfacial energy transfer, restricted component diffusion, and reduced fractional free volume ( FFV ), rather than only the intrinsic conductivity of graphene. Density functional theory (DFT) calculations further clarified the electronic origin of graphene–asphalt affinity, showing that molecular planarity, π-conjugation, and heteroatomic groups controlled the selective adsorption of asphalt components on graphene through dominant van der Waals interactions and π–π interactions. These findings establish a cross-scale correspondence among experimental performance, collective molecular transport, and molecule-specific electronic interactions, thereby clarifying the dosage-dependent balance among thermal enhancement, structural reinforcement, and deformation stability.