Performance Research of Double‐Layer Film Structure Coated Red Mud and Its Performance in Asphalt

ABSTRACT Red mud (RM), a highly alkaline alumina‐industry waste, suffers from poor compatibility with organic materials and potential heavy‐metal leaching. This study developed a hierarchical polydopamine (PDA)/γ‐aminopropyltriethoxysilane (KH550) bilayer modification strategy for asphalt application. RM was neutralized with HCl and sequentially coated with PDA and KH550. Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and leaching tests confirmed successful surface modification without substantially altering the major crystalline phases. Conventional physical tests, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) tests were used to evaluate asphalt performance. The bilayer coating reduced As Co, and V leaching by 97.4%, 88.2%, and 98.5%, respectively. Modified asphalt exhibited improved consistency, rheological response, elastic recovery, and resistance to permanent deformation. Among the tested dosages, 4% KH550‐PDA‐RM showed favorable overall performance, with a 25.6% increase in rutting factor at 46°C and improved low‐temperature flexibility. The enhancement was attributed to the RM–PDA–KH550–asphalt interfacial bridging structure, which strengthened adhesion, dispersion, and stress transfer.