Compatibility of biochar-asphalt composites for pavement applications

Fossil-derived asphalt binders require optimal stiffness for durable pavement performance. This study evaluates the use of wood-based biochar (up to 15 wt%) in a PEN50/70 binder to improve engineering properties and reduce environmental impact. Material characterization showed that increasing biochar content enhanced surface roughness, polar functional groups, and thermal residue, with 10% yielding uniform particle dispersion. Spectroscopic analysis indicated higher carbonyl functionality and reduced aromaticity, reflecting modified ageing and viscoelastic behaviour. At 10% biochar, binder stiffness improved, penetration decreased by 30%, and softening point increased by 5%. Rutting resistance increased up to this dosage, whereas non-linear stress sensitivity appeared beyond it. Glass-transition temperatures remained unchanged, suggesting no added low-temperature cracking risk. Volatile organic compounds emissions decreased by up to 64% at 10% but amplified at 15%. Life cycle assessment (ISO 14040; ReCiPe 2016) showed up to 14% reductions in climate change, resource depletion, and toxicity impacts, dominated by biochar dosage effects. • Wood-based biochar improved rutting resistance without added cracking risk. • A 10% biochar dosage achieved uniform dispersion and optimal stiffness. • Biochar addition at 10% reduced total volatile organic content emissions by 64%. • Life cycle assessment showed up to 14% lower climate and resource impacts.