Biochar as Additive and Modifier in Bitumen and Asphalt Mixtures

Incorporating biochar into pavement materials is a novel and environmentally sustainable approach that aligns with global sustainability goals and advances greener pavement technologies. Studies have shown that biochar significantly enhances the strength, durability, and stability of pavements, while also contributing to sustainability by lowering the carbon footprint associated with traditional construction materials. Additionally, the incorporation of biochar contributes to the sustainability of asphalt engineering by reducing reliance on petroleum-based products and promoting the valorization of biomass. The primary objective of this review is to critically evaluate and synthesize existing research on the use of biochar in bitumen and asphalt mixtures, identifying key performance trends, influencing factors, and optimum modification conditions. Despite these benefits, several drawbacks and challenges remain. These include variability in biochar properties, determining the optimal dosage for different applications, and the lack of standardized testing methods. This review investigates a wide range of studies and experimental investigations that evaluate the sources and production methods of biochar, as well as its effects on bitumen binders and asphalt mixtures. Furthermore, the paper highlights the environmental consideration of biochar modification, including carbon sequestration and Life cycle assessment. Substantial findings and their engineering implications are presented, along with recommendations for future research aimed at advancing the broader adoption of biochar in sustainable pavement engineering, in alignment with the principles of the circular economy.