Bidirectional thermal regulation composite modifier for asphalt: Design, controllable synthesis and temperature-regulating effect evaluation

This study addresses the controllable synthesis and temperature-regulating effect evaluation of a bidirectional thermal regulation composite modifier for asphalt. Using mineral materials and agricultural waste as raw materials, a composite asphalt modifier with hierarchical nano–micro pore structure and energy conversion capability was controllably synthesized. Temperature-regulating base functional materials were optimally selected based on their thermal conductivity and the temperature evolution during heat transfer processes. An optimal material ratio was proposed according to thermal regulation effectiveness and thermophysical parameters. A dedicated testing and evaluation method for the temperature-regulating effect of bidirectional thermal regulation modified asphalt was proposed, and the effects of material composition and preparation parameters on the thermal regulation performance of modified asphalt were systematically investigated. The optimal preparation process was identified through combined microstructural characterization and macroscopic performance assessment. The aging and pavement performance of the composite modified asphalt mixture were comprehensively evaluated. The results show that tourmaline anion powder (T), diatomite (D) and bagasse (B) are the optimal functional components. Considering thermal regulation performance, pore structure and cost efficiency, the optimal mass ratio is determined as T:D:B=5:4:1, and the optimal preparation process is mechanical dry mixing at 400 r·min -1 for 10 min. After 2 h of heating, the temperature drop of the modified asphalt exceeds 3.8 °C; after 2 h of cooling, the temperature increase is higher than 1.3 °C.When applied to the asphalt mixture, it achieves a temperature reduction of 8.6°C under heating conditions and a heat preservation of 3.3°C under cooling conditions, demonstrating a significant bidirectional thermal regulation effect alongside good aging resistance and pavement performance. This study provides a reliable technical basis for the engineering application of bidirectional thermal regulation asphalt materials.