Feasibility of reuse of modified electrolytic aluminium spent refractory material in asphalt and assessment of its environmental stability

Abstract

The central toxic part of the aluminum industry's overhaul slag, as high value-added recycling of spent refractory material (SRM), contributes to environmental protection and resource recycling. Herein, a “bayberry"-like hexamethyldisilazane-tannic acid-SRM (HMDS-TA-SRM) modifier was prepared by a simultaneous “precipitation-TA wrapping” reaction design and a secondary grafting reaction with HMDS. The design allows the material to be treated with a concentration of F− (5.93 mg/L) that meets the Chinese primary wastewater discharge standard (10 mg/L). HMDS-TA-SRM with hydrophobic (water contact angle = 104.3°) nano-sized microsphere stacking surface exhibited good interfacial interaction with the matrix bitumen. At 64 °C and 0.1 kPa and 3.2 kPa pressures, the deformation recovery capacity of the HMDS-TA modified asphalt was increased by 34.9% and 45.6% compared to that of the pristine SBS-modified asphalt, respectively. At the same time, the double wrapping of the modified film and bitumen significantly improved the sequestration capacity of hazardous substances, with a cumulative F− exudation of only 0.45% after 180 d of immersion. Attributed to the green, cost-effective and efficient modification method, the new SRM-asphalt system could be deemed of great promise for the safe application of SRM.