Sustainable modification of bitumen and asphalt mixes with kraft lignin

Abstract

Asphalt pavements are vital to modern infrastructure, but conventional methods often struggle to address growing sustainability demands while maintaining reliable performance. This PhD research aims to investigate the potential of sustainable additives, specifically Kraft lignin, to address these challenges. The research began with a preliminary investigation into Aluminosilicate, as a warm mix asphalt modifier, which lacked the necessary properties for an effective additive, prompting a shift toward Kraft lignin. The study was initiated by evaluating different lignin types and then continued in three phases, focusing on Kraft lignin. In the first phase, key properties of Kraft lignin, including particle size distribution and chemo-thermal characteristics, were investigated. Subsequently, Kraft lignin was incorporated into bitumen using two mixing protocols: high-shear mixer and mechanical mixer, to evaluate the effects of Kraft lignin and blending conditions. A comprehensive series of tests, including BRV, DSR, FTIR, ESEM, TGA, and DSC, were conducted. The results demonstrated significant influences of Kraft lignin content and blending conditions on viscosity, viscoelastic behavior, and thermal stability, while FTIR confirmed no chemical reaction with bitumen. The second phase focused on mitigating the increased viscosity observed in lignin-modified bitumen using Sasobit®. The synergistic effects of Kraft lignin and Sasobit were investigated using FTIR, TGA, BRV, DSR, MSCR, and BBR tests on bitumen. Results demonstrated that Sasobit effectively reduced the viscosity of lignin-modified bitumen, enhanced thermal stability, and improved high-temperature performance, although low-temperature performance was slightly compromised. The third phase extended the research to asphalt mixes, evaluating the combined effects of Kraft lignin and Sasobit on hot and warm mix asphalt. Four Mixes with 20 % Kraft lignin and 3 % Sasobit, were produced. Volumetric and mass properties, compactability, and construction temperatures were evaluated using the SGC. While Kraft lignin increased binder viscosity and air voids, leading to higher construction temperatures and reduced compactability, Sasobit effectively counteracted these effects. Additionally, Kraft lignin exhibited a dual role, as both a binder replacement and a filler. The combination of 20 % Kraft lignin and 3 % Sasobit demonstrated significant potential for advancing sustainable asphalt production.

Date	30 Jun 2025
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Alan Carter (Supervisor) & Jean Pascal Bilodeau (Co-supervisor)