Biochar for asphalt modification: A case of high-temperature properties improvement

Biochar has been utilized as a renewable biomass resource to develop sustainable and eco-friendly pavements. This study focuses on the influence of biochar as an asphalt modifier on the improvement of high-temperature performance of asphalt. A series of tests were performed to comprehensively evaluate the high-temperature performance of the biochar modified binder. The interaction mechanism between the biochar and the binder was explored using scanning electron microscopy and Fourier-transform infrared spectroscopy (FTIR). The results indicated that the complex modulus and penetration of the biochar-modified asphalt binder could be increased by up to 35% and 36.5%, respectively, compared with those in case of the matrix asphalt, thereby improving the deformation resistance. In addition, the observed increase in the complex modulus, rutting factor, and viscosity-temperature index contributed to the improvement of temperature sensitivity and anti-rutting properties. These relationships are attributed to the fact that biochar has a fibrous porous structure and forms a skeleton and stiffening zone in the binder. Although biochar has a negative effect on the low-temperature properties of the binder, this can be alleviated by controlling the biochar content. Moreover, the FTIR results showed that no new chemical functional groups appeared after the incorporation of biochar into the binder. The internal chemical environment of the biochar-modified asphalt binder was different from that of the matrix asphalt. In conclusion, biochar is feasible as a modifier for binders owing to its high-temperature properties.