Temperature susceptibility and structural performance of CORMBB: A bio-based asphalt binder for the paving application

The growing demand for sustainable pavement materials has increased interest in bio-based alternatives to petroleum bitumen. This study develops castor oil- and rice husk ash-modified bio-bitumen (CORMBB) by partially replacing VG-30 and evaluates its physical, chemical, temperature-dependent, and rheological properties. Temperature susceptibility was assessed using penetration index (PI), penetration viscosity-number (PVN), viscosity-temperature susceptibility (VTS), and Arrhenius activation energy, while rutting performance was evaluated using the 2.2 kPa failure-temperature criterion. The colloidal index decreased from 0.33 for the base binder to 0.26 for CORMBB-2, suggesting a more stable colloidal composition. FTIR indices showed increased aliphatic and methylene contents and reduced carbonyl and sulfoxide indices after modification. PI decreased from − 1.26 for the base binder to − 1.64 and − 2.37 for CORMBB-1 and CORMBB-2, respectively, while PVN decreased from − 10.77 to − 12.30. Activation energy decreased markedly from 57.81 kJ/mol for the base binder to 43.77 and 42.67 kJ/mol for CORMBB-1 and CORMBB-2, indicating lower viscosity sensitivity to temperature. However, the RTFOT-aged rutting failure temperature declined from 94.7 °C for the base binder to 76.7 °C and 74.1 °C for CORMBB-1 and CORMBB-2, respectively. Overall, CORMBB showed improved thermo-viscous response but reduced high-temperature rutting resistance, highlighting a trade-off between temperature sensitivity and stiffness.