Document Type : Research Paper
Authors
1
Department of Road and Transportation, Faculty of Civil Engineering, Semnan University, Iran
2
Faculty of Civil Engineering, Semnan University, Semnan, Iran
3
Department of Civil Engineering, University of Guilan, Rasht, Iran
Abstract
Incorporating recycled asphalt pavement (RAP) into asphalt mixtures is a common practice for sustainability; however, aging and harden-ing of the RAP binder can compromise performance. Aged RAP is stiffer, less flexible, and more prone to cracking. This research inves-tigates the combined effects of RAP content, RAP age, and nano-silica (SiO₂) addition on asphalt performance, focusing on fracture re-sistance, fatigue resistance, and moisture susceptibility. Asphalt mix-tures containing 25%, 50%, and 75% RAP were evaluated using RAP aged 5 and 10 years. Nano-SiO₂ was incorporated at 0%, 1%, 1.5%, and 2%. Performance evaluations included 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 sus-ceptibility. The findings indicated that Nano-SiO₂ significantly en-hanced fracture and fatigue resistance, especially at lower RAP con-tent. At 25% RAP, 1.5% and 2% Nano-SiO₂ improved both fracture and fatigue resistance by 15-20%. Notable enhancements were ob-served for mixtures with 50% and 75% RAP, with optimal results at 2% nano-silica. Furthermore, Nano-SiO₂ improved moisture re-sistance, increasing TSR values above 80%. Nano-silica effectively mitigated aging effects, particularly in mixtures with higher RAP con-tent. Based on this analysis, utilizing 25-50% RAP combined with 1.5% Nano-SiO₂ is advisable for producing high-performance as-phalt mixtures.
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