Comprehensive Assessment of Nano-Silica Modified Asphalt Mixtures: Influence of RAP Content, Aging, and Performance Characteristics

Using recycled asphalt pavement (RAP) in asphalt mixtures is common for improving sustainability, but it can lower performance because of the aging and hardening of RAP binder. Aged RAP is stiffer, less flexible, and more prone to cracking. The performance decreases with the age of RAP. Adding materials like nano-materials can help reduce these issues. This study investigates the combined impact of RAP content, RAP age, and Nano-silica (SiO₂) on asphalt performance, focusing on fracture resistance, fatigue resistance, and moisture susceptibility. Asphalt mixtures with ۲۵%, ۵۰%, and ۷۵% RAP were tested using two types of RAPs with different ages (۵ and ۱۰ years). Nano-SiO₂ was added in varying percentages (۰%, ۱%, ۱.۵%, and ۲%) to evaluate its effects. The performance was assessed using the semi-circular bending test for fracture resistance, the indirect tensile fatigue test for fatigue resistance, and the tensile strength ratio (TSR) test for moisture susceptibility. Results showed that Nano-SiO₂ improved the fracture and fatigue resistance of mixtures, especially those with lower RAP content. At ۲۵% RAP, the addition of ۱.۵% and ۲% Nano-SiO₂ enhanced fracture and fatigue resistance by ۱۵-۲۰%. For mixtures with ۵۰% and ۷۵% RAP, Nano-SiO₂ led to significant improvements, with the best results seen at ۲% nano-silica. Nano-SiO₂ also enhanced moisture resistance, increasing TSR values above the ۸۰% threshold. Nano-silica mitigated the effects of aging, particularly in mixtures with higher RAP content. According to this comprehensive evaluation, it is recommended to use ۲۵-۵۰% of RAP using ۱.۵% of Nano-SiO₂ to achieve high-performance mixtures.

کلیدواژه ها:

Aging effect ، Nano-silica ، Fracture resistance ، Fatigue life ، Moisture susceptibility