Investigation on the characteristics and effect of plant fibers on the properties of asphalt binders

In this paper, the effect of five different plant fibers on the performance of asphalt binder was evaluated. During the research, the microstructure, components and thermal stability of these fibers were studied by Scanning Electron Microscopy, Fourier Transform Infrared Spectrometer and thermogravimetric analysis. The surface energy characteristics of five plant fibers was investigate by a contact angle test. To estimate the performance of five plant fiber asphalt binders, the cone penetration test, temperature sweep test, multiple stress creep recovery test and bending beam rheometer test were carried out. Results showed that bagasse fiber, corn straw fiber and cotton straw fiber presented hollow structure and their surface textures were rougher than bamboo fiber and lignin fiber. The functional group compositions of five plant fibers showed high similarity and the main components of these fibers were celluloses, hemicelluloses and lignin. All these fibers had good thermostability at working temperature. Within five plant fibers, corn straw fiber possessed the highest amount of surface free energy, which led to the best adhesion with asphalt binder. After applying these plant fibers, the toughness and permanent deformation resistance of asphalt binders were improved. Whereas, the low-temperature properties of fiber modified asphalt binders degraded. Within five plant fibers, corn straw fiber can better improve the road performance of asphalt binder. However, corn straw fiber was more vulnerable to moisture damage, which had adverse impacts on the water damage resistance of asphalt binder.