Thermal conductivity of reclaimed asphalt pavement and its constituents using finite element modelling approach

Reclaimed Asphalt Pavement (RAP) is increasingly used in new asphalt mixtures to reduce environmental impacts, but effective blending of aged binder remains challenging due to RAP’s thermal behaviour. This study develops a methodology to quantify RAP thermal conductivity using finite element modelling (FEM) validated by laboratory tests. Bulk thermal conductivity of RAP particles and aged binder was measured through parallel-plate heating, and a three-dimensional ANSYS FEM model was developed to back-calculate particle and binder conductivities. By assuming spherical particles in cubic packing and varying binder film thickness, the model produced binder thermal conductivities consistent with laboratory results (∼0.17 W/m·K). Predictions were further validated with the Generalised Self-Consistent Model (GSCM), which also estimated film thicknesses across particle sizes. Results show that thermal conductivity increases with density, decreases with air void content, and is higher for larger particles.