Sustainable Bitumen Modification Using Bio-Based Adhesion Promoters

The growing emphasis on sustainable road construction has stimulated interest in environmentally friendly bitumen modifiers. This study presents the development of biodegradable adhesion promoters synthesized via the amidation of renewable raw materials (rapeseed oil and higher fatty acids) with polyethylene polyamine. The main objective was to improve bitumen–aggregate adhesion while maintaining the essential physico-mechanical and rheological properties of the bitumen. The synthesized bio-based adhesion promoters were incorporated into penetration-grade bitumen at a dosage of 0.4 wt.%. Physico-mechanical testing confirmed that their inclusion does not significantly affect the fundamental properties of the bitumen, while substantially enhancing adhesion to both glass and mineral aggregates. Rheological analysis showed that the rapeseed oil-based adhesion promoter had minimal influence on viscoelastic behavior. In contrast, the fatty acid-based promoter increased the rutting resistance parameter (|G*|/sinδ) and decreased the phase angle (δ), indicating improved resistance to permanent deformation. FTIR spectroscopy further revealed that the fatty acid-based adhesion promoter significantly reduced the formation of carbonyl groups during short-term aging, suggesting a retardation in oxidative aging and potential rejuvenating effects. In conclusion, the proposed bio-based adhesion promoters, derived from renewable sources and fully biodegradable, represent a promising solution for enhancing bitumen performance and supporting the durability and sustainability of asphalt pavements.