Document Type : Regular Paper
Authors
1
Ph.D. Candidate, Faculty of Civil Engineering, Semnan University, Semnan, Iran
2
Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
3
Department of Civil Engineering, University of Guilan, Rasht, Iran
Abstract
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 25%, 50%, and 75% RAP were tested using two types of RAPs with different ages (5 and 10 years). Nano-SiO₂ was added in varying percentages (0%, 1%, 1.5%, and 2%) 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 25% RAP, the addition of 1.5% and 2% Nano-SiO₂ enhanced fracture and fatigue resistance by 15-20%. For mixtures with 50% and 75% RAP, Nano-SiO₂ led to significant improvements, with the best results seen at 2% nano-silica. Nano-SiO₂ also enhanced moisture resistance, increasing TSR values above the 80% 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 25-50% of RAP using 1.5% of Nano-SiO₂ to achieve high-performance mixtures.
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