Investigation of Properties of Long-Chain Organic Modified Red Mud and Waste Rubber Powder Composite Recycled Asphalt: Toward to Sustainable Pavement Materials

To enhance the storage stability, physical rheological properties, and antiaging performance of waste rubber powder modified asphalt, this study employed long-chain silane coupling agents (C6TMS and C16TMS) for surface modification of red mud (RM), successfully preparing organic-modified red mud (C6RM/C16RM). FTIR and XRD analyses confirmed that silane chains were successfully grafted onto the RM surface without altering its crystalline structure. SEM and particle size analysis revealed significantly improved dispersion of the modified red mud, while water contact angle tests indicated marked enhancement of its hydrophobicity. When C6RM/C16RM was compounded with waste rubber powder for aged asphalt regeneration, results showed that modified red mud substantially improved the comprehensive performance of recycled asphalt. Notably, C16RM demonstrated superior effects by enhancing asphalt's storage stability, rheological properties, and antiaging performance. Mechanism analysis revealed that the long organic chains of red mud intertwined within the asphalt matrix, forming a cross-link-like network structure that effectively inhibited rubber powder sedimentation and improved system stability. Additionally, the porous structure and uniform dispersion of modified red mud in asphalt hindered oxygen/heat penetration and adsorbed light components, thereby delaying asphalt aging. This research provides an effective strategy for improving waste rubber powder modified asphalt performance while achieving resource utilization of red mud, carrying significant environmental and economic value.