Finite element modeling of particle-scale heating of reclaimed asphalt pavement (RAP) in drum plants considering size, material, and internal temperature gradients

Heating reclaimed asphalt pavement (RAP) in drum plants is essential for binder activation and mixture homogeneity, yet the mechanisms governing particle-scale heating remain insufficiently understood. This study developed a finite element method (FEM) framework in ANSYS to simulate the transient heating of RAP, virgin aggregates, and composite particles inside a virtual asphalt drum. Three particle types were investigated: pure aggregates (limestone and taconite), homogeneous RAP particles, and composite particles consisting of aggregates coated with a thin asphalt film. Convective heating was modeled with a decaying drum gas temperature profile, and temperature evolution was tracked at particle centers and edges. Results indicate that particle size and thermal conductivity strongly influence heating efficiency. Taconite aggregates heat more rapidly than limestone due to higher conductivity, while homogeneous RAP particles heat faster than composites but remain far below mixing temperatures within typical drum residence times. Edge–center temperature differences (ΔT) revealed persistent thermal nonuniformity in larger RAP particles, suggesting incomplete binder mobilization. Comparisons with a simplified analytical conduction model showed that analytical predictions consistently underestimated heating times relative to FEM, owing to the assumption of perfect thermal contact. These findings emphasize the need to consider particle-scale heat transfer when evaluating drum recycling performance. Practical implications include promoting RAP fractionation, considering aggregate types with higher conductivity, and developing preheating or drum design modifications to improve binder blending and enable greater RAP utilization in sustainable asphalt mixtures.