Performance Properties of a Hot-Mix Asphalt Modified with Oil Palm Kernel Shell–Based Biochar for Road Pavements

Waste biomass generation from agro-industrial activities has increased due to the world’s population growth. To reduce the negative environmental impacts, these biomasses can be treated and thermally decomposed by pyrolysis to convert them into biochar (BC), which is a material that shows interesting properties and is compatible with asphalt binders. In the present study, asphalt cement (AC 60-70) was modified with a BC obtained from oil palm kernel shell (BC-PKS). This modified asphalt binder was named AC-BC. No research has used this type of BC as a modifier of asphalt binders. For the modification, 10% BC-PKS was used for the binder’s total mass. Conventional physical characterization tests (penetration, viscosity, softening point, ductility, among others) were carried out on AC 60-70 and AC-BC. Scanning electron microscope (SEM) visualizations were performed on the BC-PKS and the AC-BC. Then a hot-mix asphalt (HMA) was manufactured using AC-BC (called HMA-BC). The main objective of the study was to evaluate the mechanical performance of the HMA-BC mixture by performing tests under monotonic loading [Marshall and indirect tensile strength in dry condition (ITSD) and wet condition (ITSW)] and cyclic loading [resilient modulus (RM), permanent deformation, and fatigue under stress-controlled mode]. The Cantabro test was also performed, and the tensile strength ratio (TSR) was calculated. The results were compared with those obtained on a control mix (HMA manufactured with unmodified AC 60-70). ANOVA was performed to evaluate whether BC-PKS generated significant changes in the HMA-BC properties. As a general conclusion, it is reported that BC-PKS is a promising asphalt binder modifier that inclines to increase its stiffness. Furthermore, AC-BC generated an HMA-BC with higher stiffness under cyclic loading (RM) and higher resistance to permanent deformation, moisture damage, abrasive wear, and fatigue compared to the control mix. This improved performance was achieved without the need to (1) increase the optimum asphalt binder content (OAC), (2) change the volumetric composition of the HMA, and (3) increase the mixing and compaction temperatures.