Silica Microcapsules Containing Waste Soybean Cooking Oil with Enhanced Thermal Stability, Environmental Resistance, and Sustained-Release for Superior Bitumen Anti-Aging Performance

Bitumen oxidative aging leads to pavement deterioration through increased stiffness and cracking, necessitating effective rejuvenation strategies. Current approaches utilizing waste soybean cooking oil (WSCO) are limited by rapid evaporation and leaching. This study presents an innovative solution through silica microencapsulation of waste soybean cooking oil (microWSCOs) synthesized via optimized oil-in-water emulsion with tetraethyl orthosilicate. The microcapsules exhibit uniform spherical morphology (10-50 μm diameter) with high encapsulation efficiency (92±3%) and thermal stability (<5% mass loss at 180°C for 2 h). Controlled release kinetics under simulated traffic loading (0.7 MPa, 10 Hz) demonstrate 62.4±2.1% cumulative rejuvenator release after 10,000 cycles, effectively restoring aged bitumen properties: softening point reduction of 15.2±0.8°C, penetration increase of 28.3±1.5%, and complex modulus decrease of 34.7±2.3%. Environmental resistance testing reveals 89.2±3.5% WSCO retention following 500 h UV irradiation (0.89 W/m²) and 7-day water immersion. The microencapsulation system demonstrates dual sustainability benefits by valorizing waste oil while significantly extending pavement service life through targeted, long-term rejuvenation.