Valorizing renewable tall oil pitch as asphalt extenders to improve road durability

Asphalt binders are petroleum-derived materials whose continued consumption raises concerns regarding resource security and sustainability in road construction. Tall oil pitch (TOP), a bio-based by-product of the pulp and paper industry, offers a promising pathway to partially replace fossil-derived binders through asphalt blending. In this study, three TOP-asphalt composite binders were developed and systematically evaluated with different aging states by molecular dynamics simulations, fourier transform infrared spectroscopy, and rheology. The results show that TOP incorporation slightly decreases high-temperature rutting resistance but leads to a marked enhancement in cracking resistance. TOP shows limited sensitivity to oxidation, and the aging mechanism of TOP-modified binders is broadly consistent with that of neat binders. TOP increases free volume and molecular mobility while reducing cohesion, thereby mitigating aging-induced hardening and limiting asphaltene aggregation to maintain colloidal stability. This work provides a sustainable strategy for valorizing bio-based by-products and reducing reliance on fossil resources.