Microscale interface mechanism of the improved high and low-temperature performance of modified bamboo fibres-reinforced asphalt mixture

Using plant fibres to reinforce asphalt mixture and improve its road performance has attracted growing interest. To improve the interfacial adhesion between bamboo fibres (BFs) and asphalt matrix, BFs were treated with acrylate epoxidized soybean oil (AESO) and 4,4'-diphenyl methane diisocyanate (MDI). The high-temperature stability and low-temperature cracking resistance of the modified BFs-reinforced asphalt mixture were evaluated by the rutting and bending experiments, respectively. The dynamic stability at 60°C and the flexural strength at −10°C of the mixture with modified BFs were improved by 21.67% and 22.84%, respectively. Then, molecular dynamic simulations were implemented to investigate the effect of fiber modification on the interface properties. Simulation results showed that as the grafting density increased from 0 to 2.21 × 10–7 mol/m2, the binding energy increased by 277.2% and 159.3% at 65°C and −15°C, respectively, and the diffusion coefficient decreased by 50.8% and 27.7% at 65°C and −15°C, respectively. As the grafting density further increased to 4.43 × 10−7 mol/m2, the interface performance deteriorated because the dense grafted molecular chains inhibited the diffusion of asphalt to BF surfaces. This work provides an understanding of the interfacial mechanism for optimising the BF-reinforced asphalt mixtures.