Study of the Physical and Mechanical Properties of Lignin-Modified Bitumen

Lignin, a prominent by-product of the wood and paper industry, presents a promising alternative to bitumen or a modifier to enhance the performance of bituminous mixtures. As a natural biopolymer, lignin offers the dual benefits of improving the properties of bituminous materials while promoting environmental sustainability. This study investigates the use of two types of lignin (lignin A and lignin B) as additives to enhance the characteristics of bitumen and the performance of bituminous mixtures. Various weight percentages of lignin were incorporated into control bitumen (VG30) at levels of 5%, 10%, and 20%. The effects of lignin on bitumen properties were assessed through penetration tests, softening point evaluations, ductility measurements, and elastic recovery analysis. Following this, bituminous mixtures were formulated, and their performance was evaluated using tests such as Marshall stability, flow value, resilient modulus, crack tolerance index, indirect tensile strength (ITS), and Cantabro abrasion tests. The experimental results indicate that adding lignin to bitumen significantly improves both the physical and mechanical properties of the material. Specifically, incorporating up to 10% lignin in both modified bitumen types resulted in increased Marshall stability and reduced flow values, suggesting enhanced resistance to permanent deformation. Moreover, the ITS of the bitumen improved with a 10% lignin modification. Notably, lignin B at 10% content exhibited the highest resilient modulus, indicating improved cohesion and structural integrity, which contributed to increased stiffness. Furthermore, the lignin-modified bitumen demonstrated superior adhesion to aggregates compared to the control bitumen. As the lignin content increased, the fracture energy consistently increased, reflecting an enhanced resistance to crack initiation and propagation. This finding suggests that lignin inclusion contributes to the toughness of the asphalt mixture, enhancing its resilience against cracking. In addition, a significant reduction in mass loss was observed, particularly at higher lignin contents, highlighting the material’s decreased susceptibility to abrasion and wear. Overall, these results underscore the substantial impact of lignin on improving the durability and performance of bituminous mixtures.