Influence of Biomass Type on the Mechanical Performance of Biochar-Modified Hot-Mix Asphalt

The increasing generation of agricultural residues and the need to reduce the environmental footprint of road infrastructure have stimulated the search for sustainable modifiers for asphalt materials. Biochar (BC), a carbon-rich material produced through biomass pyrolysis, has emerged as a promising additive for asphalt binders and mixtures because of its porous structure, high carbon content, and physicochemical compatibility with bituminous matrices. However, limited research has systematically evaluated the influence of biomass type on the mechanical performance of hot-mix asphalt (HMA). This study investigated the effect of BC derived from four biomasses—rice husk (RH), oil palm kernel shell (OPKS), oil palm mesocarp fiber (OPMF), and pine wood shavings (PWS)—on the performance of HMA produced with modified asphalt cement (AC). Based on binder characterization, a BC content of 10 % by weight of AC was selected as the most suitable dosage. Conventional and rheological tests were performed on modified binders, whereas HMA performance was evaluated through Marshall, indirect tensile strength, resilient modulus, rutting resistance, fatigue resistance, moisture susceptibility, and Cantabro loss. Statistical analyses were conducted using analysis of variance. Results showed that BCs increased binder stiffness, improved rutting resistance, and enhanced the mechanical performance of HMAs, particularly in rutting and fatigue resistance. No significant differences were observed in resistance to moisture damage and raveling. BCs derived from RH and OPKS provided the greatest improvements, whereas OPMF and PWS showed moderate gains. Additionally, pavement design results indicated slight reductions in asphalt layer thickness and costs, highlighting technical, economic, and environmental benefits under tropical conditions.