Anti-aging mechanism of polyurethane/graphene oxide composite modified asphalt: insights from experiments and molecular simulation

To enhance the thermo-oxidative aging resistance of asphalt while maintaining its excellent high- and low-temperature performance, polyurethane (PU) and graphene oxide (GO) were used for asphalt modification. The physical, rheological, and anti-aging properties of PU/GO composite modified asphalt were investigated, while the Fourier-transform infrared spectroscopy test and the molecular simulation were employed to explore the modification mechanism of PU and GO. Results show that PU and GO alter the viscoelastic fraction of asphalt, which provides it with excellent high-temperature stability and low-temperature performance. Moreover, PU can reduce the intermolecular gaps and strengthen van der Waals interactions within asphalt, which decreases its free volume and increases its cohesive energy. The addition of GO can promote the aggregation of asphaltenes, enhancing the stability of asphalt. The synergistic modification mechanism of PU and GO decreases the free volume and molecular gaps in asphalt, while suppressing oxygen diffusion and the formation of carbonyl and sulfoxide groups during thermo-oxidative aging. This synergistic effect improves the thermo-oxidative aging resistance of asphalt. These findings provide new insights and a promising strategy for developing durable asphalt through experimental and theoretical approaches.