Effect of lignin content on the performance grade and stability of asphalt binders used in Thunder Bay

Abstract

The design roads relies solely on bitumen as a binding agent because it provides superior adhesive properties and waterproofing capabilities. The main source of bitumen production from crude oil oil refining results in expensive production costs and supply chain problems and reduced refining capabilities. The worldwide transition toward sustainable infrastructure solutions and environmentally responsible construction materials has become more urgent because of these challenges. The paper industry produces lignin as a renewable biopolymer which shows promise as a bitumen extender because of its structural compatibility and sustainability advantages. The research evaluates the addition of kraft lignin at 10%, 20%, and 30% levels in asphalt mixtures to determine their performance against Ontario's Ministry of Transportation (MTO) Performance Grade (PG) standards for cold climate applications in Thunder Bay. The primary objective of this study is to determine whether lignin-modified asphalt (LMA) meets structural and performance standards while providing a sustainable alternative to traditional binders. The primary objective is to determine whether lignin-modified asphalt (LMA) can meet structural and performance standards while providing a sustainable alternative to traditional binders. The primary objective is to determine whether lignin-modified asphalt (LMA) meets structural and performance requirements while serving as a sustainable alternative to conventional binders. A hybrid methodology was adopted, involving both practical and theoretical approaches. The experimental component consisted of mix design tests using PG 52-34 bitumen and kraft lignin, including Marshall Stability and Superpave Gyratory Compactor methods. These tests examined workability, compaction, and strength parameters. For the theoretical analysis, secondary data from FPInnovations was used to evaluate rheological properties, oxidative aging resistance, and PG classification shifts. Results indicated that a 20% lignin substitution level provided the most balanced performance, achieving optimal Marshall stability, acceptable air voids, and good compaction. Theoretical data supported improvements in high-temperature PG ratings (e.g., PG 58-28) and enhanced resistance to rutting and oxidative aging at moderate levels of substitution. This research will provide valuable insights into the mechanical viability and environmental potential of LMA. The findings support the use of Lignin as a partial bitumen substitute and offer a foundation for future research and performance-based implementation strategies in cold-region pavement applications.