Investigation of heat transfer performance of asphalt pavements at different compaction levels based on CT reconstruction

Heat transfer during the heating stage of hot in place recycling (HIR) is strongly affected by compaction induced mesostructural heterogeneity, which can cause nonuniform temperature fields and local overheating. Accordingly, industrial CT scanning and image reconstruction were combined with a two step joint filtering algorithm and a three phase segmentation method using channel level and object level operations to build high fidelity 3D mesostructural models at different compaction levels. A 3D transient heterogeneous heat transfer model was then developed and solved using a finite difference scheme. Measured thermal properties and controlled heating tests validate the model, with relative errors below 5.76% and temperature RMSE values of 0.0756 °C at 2 cm and 0.0275 °C at 4 cm. Simulations indicate that increasing compaction improves heating uniformity, flattens isothermal surfaces, and suppresses surface overheating, whereas low compaction specimens exhibit pronounced spatial temperature fluctuations. At the mesoscale, aggregates provide the primary conductive skeleton, asphalt mastic forms conductive bridges between aggregates, and air voids dominate thermal resistance. These findings quantify how compaction and mesostructure jointly govern pavement thermal response and support parameter optimization for HIR heating.