Unravelling the efficient use of waste lignin as a bitumen modifier for sustainable roads

The high cost and the environmental impact associated with using petroleum bitumen in pavement construction is a problem facing the asphalt industry. The study analyzes the effects of waste lignin on the properties (characterization, morphology, decomposition behavior, low and high-temperature behavior, fatigue resistance, deformation, adhesion bonding with aggregate in the presence of water and storage stability) of bitumen binders. The results show that increasing the lignin content, increased the cohesion and stiffening of the binder. Adding 10% lignin had a negligible influence on the workability and compaction characteristics of the asphalt mixture. The flow characteristics, of the lignin bitumen composite (LBC), at low and high temperature, decreased with increasing lignin content. Furthermore, the lignin fibers decreased the decomposition rate of the binder thus reducing the volatility of the binder (C0₂ emissions). Dynamic Shear Rheometer test results revealed that adding lignin fibers to bitumen increased the rutting resistance of the binder while the linear amplitude sweep (LAS) results showed a decrease in the fatigue resistance. The multiple stress creep recovery (MSCR) results showed that LBC binder recovered better than the pure bitumen. In addition, LBC binder deformed less at different temperatures and stress levels. The LBC binder also had a better adhesion with aggregate as compared to bitumen. The study provides baseline information that complements past studies and can be useful to all stakeholders in the asphalt industry.