Optical and rheological properties of carbon quantum dots regenerated aged asphalt based on molecular simulation and experiments

To investigate the rheological and optical properties of carbon quantum dots (CQDs)-regenerated aged asphalt (CQDsRA), four types of CQDs, C₃₄H₁₄O₂ (CQDs-1), C₅₂H₇₂O₁₄ (CQDs-2), C₃₉H₃₀N₆O₁₀ (CQDs-3), and C₅₂H₇₂O₁₀S₄ (CQDs-4), were employed to regenerate aged base asphalt using first-principles calculations and molecular dynamics simulations. The optical properties of both the CQDs and the resulting CQDsRA, including band structure, electron density, molecular orbitals, and optical responses, were systematically examined. The results reveal that the type of CQDs significantly influences the optical response of CQDsRA. Moreover, the different CQDs also markedly affect the fundamental properties and regeneration efficacy of the modified asphalt. Among the four types, CQDs-4 exhibits the strongest fluorescence intensity, whereas CQDs-1 shows the weakest. The molecular trajectories of the CQDs resemble those of a standard pyrometric cone during the regeneration process. Additionally, the chemical reactions occur between the CQDs and the aged asphalt, leading to the formation of a cross-linked network structure.