Characterization and Evaluation of Agar as a Bio-Based Asphalt Binder Alternative

Over 90% of roads in the United States are surfaced with asphaltic materials that use petroleum-based asphalt binders, a material with high negative environmental impacts and costs. Biopolymers are a sustainable alternative, as they are sourced from renewable materials and offer the potential to reduce carbon footprint. However, their performance and durability in construction applications remain insufficiently understood. This study analyzes the potential of agar, a biopolymer extracted from red seaweed, to serve as a direct and sustainable replacement for asphalt binders. The study characterizes the rheological properties and durability of agar-based binders and the mechanical and microstructural properties of composites. The study found that agar-based binders exhibited resistance to fungal deterioration, adequate stiffness to resist rutting at temperatures up to 80 °C, and potential for energy efficiencies associated with lower mixing and compacting temperatures. Results indicate that agar-based composites illustrate many properties in line with those of traditional engineering materials. Overall, these results suggest that agar-based materials exhibit promising fresh-state and biodeterioration resistance properties to serve as a sustainable alternative to traditional, petroleum-based asphalt binders.