Performance Enhancement of Asphalt Mixtures Enabled by Bamboo Fibers and Acrylated Epoxidized Soybean Oil

Bamboo fibers (BFs) have attracted much attention as a potential sustainable reinforcement material for asphalt pavements due to their high specific strength and modulus, low cost, renewability, and biodegradability. However, the key challenge of using BFs in asphalt mixtures is the weak interfacial adhesion between intrinsically hydrophilic BFs and the hydrophobic asphalt matrix. Therefore, this study proposed a surface modification method of BFs using acrylated epoxidized soybean oil (AESO) and 4,4-methylenediphenyl diisocyanate (MDI) to improve the fiber–matrix adhesion of the BFs/asphalt mixture. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses confirmed that the modified BF surface was grafted with AESO, and both of them were linked by MDI, thereby leading to the formation of a hydrophobic layer on the fiber surface. The water absorption of BFs significantly decreased after modification, and the interfacial adhesion between the modified BFs and the asphalt matrix remarkably improved. Adding the modified BFs to the mixture improved its mechanical properties, high-temperature stability, and low-temperature cracking resistance and decreased its moisture susceptibility. The work provides a feasible and industrial-scale method to enhance the road performance of the asphalt mixture by using renewable natural fibers and vegetable oils as modifying materials.