Mechanical and electromagnetic performance assessment of magnetite-modified asphalt mixtures for electrified pavement applications

The integration of wireless power transfer (WPT) systems into pavements requires materials that enhance electromagnetic coupling while maintaining structural performance within standard durability limits. This study evaluates AC16 asphalt mixtures incorporating synthetic magnetite (Fe₃O₄) as a filler at 0–100 % volumetric replacement of calcium carbonate, with the objective of identifying magnetite contents that enhance WPT efficiency without compromising key mechanical performance criteria. Electromagnetic performance was first assessed using a resonant double-coil setup at 85 kHz. Magnetite improved inductive coupling, with received power increasing up to + 17.6 % relative to the air-gap baseline and power transfer efficiency rising by + 2–3.5 %. Mechanical performance was subsequently evaluated through Marshall stability, volumetric properties, resilient modulus, indirect tensile strength ratio (ITSR), and rutting resistance. At 50 % magnetite substitution and 4.6 % bitumen content, mixtures achieved a resilient modulus of approximately 6100 MPa, air voids close to 4 %, and ITSR values slightly above 100 %, attributed to reduced interconnected porosity and improved filler packing after moisture conditioning. Rutting resistance improved markedly, with rut depth reduced to 1.74 mm, although the wheel-tracking slope (0.08 mm/1000 cycles) remained slightly above the Spanish specification limit. Overall, the results demonstrate that magnetite-modified asphalt mixtures can enhance inductive power transfer while maintaining mechanical performance compatible with electrified pavement applications.