Effects of bio-nano ashes and nano limestone on the tensile metrics and rheological parameters as a measure of bitumen performance

Early pavement deterioration remains a major challenge in asphalt pavement construction, primarily due to temperature-induced distresses such as rutting and fatigue cracking. Conventional bitumen modification methods have been improving bitumen performance, but often rely on non-renewable or environmentally harmful additives. This study introduces a novel bio-nano ash (BNA) derived from coffee husk ash (CHA) and wood ash (WA) as a suitable bio-nanomaterial for bitumen modification, compared with mineral nano limestone (LS). The bio-nano ashes were prepared by controlled burning in a closed chamber to minimize CO2 emission and secure eco-friendly synthesis. The 70/100 pen bitumen was modified with nanomaterials at 1.5%, 3.5%, and 5.5% by weight of bitumen. The additives were characterized using X-Ray diffraction (XRD), scanning electron macroscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer, Emmette, and Teller method (BET) analysis. Rheological properties of modified bitumen were evaluated using a dynamic shear rheometer (DSR) and the Bitumen-Fast-Characterization test (BTSV). Results revealed that BNA significantly enhanced the tensile maximum force (Fmax) and rutting resistance of modified bitumen compared with nano LS, due to increased complex shear modulus, elevated Equi-shear modulus temperature (TBTSV) and reduced phase angle (δBTSV). At 5.5% WA, the maximum peak force and cumulative area were observed, indicating excellent energy absorption and the best overall mechanical performance of modified bitumen. The values of (R2 = 0.999) from linear regression confirmed a strong, consistent link between mechanical and rheological parameters, evidencing bio-nano ash from bio-waste as a high-performance, eco-friendly bitumen modified supporting sustainable asphalt engineering.