Preparation and mechanical properties of asphalt mixtures reinforced by modified bamboo fibers

Cracking resistance and durability are the main concerns in asphalt mixture for pavement. The addition of fibers is an effective way for reinforcing asphalt mixture. Bamboo fibers (BFs) show unique characteristics such as high specific strength and modulus, renewability and low cost. Thus, BFs mechanically extracted from green bamboos were used to improve the mechanical properties of asphalt mixture and thus increase the service life of asphalt pavement. For improving the poor interfacial adhesion resulted from the hydrophobicity of asphalt and the hydrophilicity of BFs, a melamine-formaldehyde (MF) copolymer was synthesized and used to modify the BFs. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectronic spectroscopy (XPS), and nuclear magnetic resonance (NMR) analyses were conducted to reveal the surface chemistry of BFs. The results proved that the MF copolymer was grafted onto the surface of BFs via the formation of covalent bonding between hydroxyl groups of BFs and amino group of melamine. The mechanical properties of the asphalt mixture were evaluated by Marshall stability, direct tensile, and indirect tensile tests. Results showed that the addition of modified BFs increased the stability and the tensile strength of the asphalt mixture. SEM images of the fractured surface of asphalt mixture indicated that strong adhesion was formed between the modified BFs and asphalt matrices. (C) 2021 Elsevier Ltd. All rights reserved.