Hydrothermal carbonization of waste wood: Sustainable recycling of biomass by-products and novel performance enhancer for bitumen

Recycling biomass by-products into bitumen is one of the most effective ways to develop sustainable pavements. To cope with the shortage of petroleum resources and improper disposal of discarded biomass, the hydrothermal carbon (HTC) produced by hydrothermal carbonization of waste wood was adopted to reduce the consumption of bitumen and enhance the performance of bitumen, and the mechanical performances and working mechanism of hydrothermal carbon-modified bitumen (HTCMB) were investigated in this study. The results indicate that HTC significantly enhances bitumen's high-temperature and fatigue properties. When the content of HTC is not more than 3%, its effect on the low-temperature cracking resistance of bitumen can be ignored. The addition of HTC absorbs the polar components in bitumen, thus promoting the dispersion of polar components and effectively preventing the mutual aggregation and crystallization of wax components and asphaltenes in bitumen. The excellent mechanical properties of HTCMB can be attributed to the irregular fibrous composition and porous structures of HTC, which play a good role in reinforcing and connecting the bitumen matrix and dramatically enhances the interaction with bitumen. This study proposes a win-win solution to the shortage of petroleum resources in road engineering and the improper disposal of discarded biomass.