Integrating waste materials into road infrastructure is essential for environmental sustainability and resource efficiency. This study addresses the modification of short-term-aged 50/70-penetration-grade bitumen using two sustainable additives: waste toner powder and lignin. Waste toner was added at weight percentages of 4%, 8%, 12%, and 16%, while lignin was added at 15% and 20%. Since these modifiers have individual uses, this study examines how they may strengthen the oxidized binder. It focuses on extending the lifespan of the mixture by combining industrial and bio-based polymers. The main aim was to delineate the impact of these modifiers on the physical consistency, low-temperature flexibility, and microstructural morphology of the binder. The results show that both modifiers increase binder stiffness by reducing penetration at all modification rates. The resins in the waste toner enhance the polymer matrix, and the lignin’s aromatic structure increases the elastic components, improving high-temperature stability. However, ductility tests showed a reduction in elongation capability, suggesting a brittle state at lower temperatures. Also, waste toner additive is identified as the ideal modifier for high-temperature applications. SEM analysis illuminated the mechanisms underlying these performance modifications. Both additives had homogeneous distribution and good bitumen matrix interfacial bonding at lower concentrations.

Globally, sustainability is an important issue. Bitumen is obtained from crude oil, is solid at ambient temperature, almost completely soluble in toluene, is in a non-volatile, sticky form, and is defined as a waterproofing material. In terms of low carbon dioxide emissions, the asphalt industry is looking for more sustainable options. Lignin is one of the most common natural polymers on earth. Its role is to hold the chemical components, which is the wall material, together in the matrix structure in plant cells and to provide resistance. Millions of tons of lignin are released after pulp production which is considered waste material. Depolymerized fractions cause significant environmental problems due to toxic chemical structures. In this study, short-term aged bitumen was modified by lignin at the rates of 15% and 20% to bitumen weight, and conventional Penetration Test, Ductility Test, and Scanning Electron Microscope (SEM) analysis were carried out to determine the rheological effect. In addition, it was aimed at determining the effective rate of lignin usage. In conclusion, the current research aimed to demonstrate that lignin, as a value-added modifier, is a promising solution with both environmental and engineering values. Also, as the lignin rate increased, the hardening rate of short-term aged bitumen increased in both penetration and ductility tests. Furthermore, SEM data revealed that particles with irregular surfaces are homogeneously distributed in aged bitumen. However, with the increase in usage rate, the distribution of lignin particles in bitumen became irregular.