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Abstract. Annually, approximately 120 million tons of asphalt pavement are milled, resulting in the generation of Reclaimed Asphalt Pavement (RAP). Despite its advantages, fully maximizing RAP usage poses challenges, particularly as RAP content exceeds 20%, leading to a reduction in pavement resistance to cracking. The aging of asphalt binder, which causes increased stiffness and susceptibility to cracking, is a primary contributing factor. Engineers addressing high RAP content must select a softer virgin binder or incorporate a recycling additive into mix designs. Bio-oil additives, derived from plant or animal sources, are known for their ability to modify asphalt binders, enhancing rheological characteristics, temperature susceptibility, and aging resistance. This study focuses on assessing the effectiveness of a bio-oil additive in producing asphalt mixtures with significant RAP proportions, with an emphasis on fracture behavior. Two reference mixtures were examined: one without RAP and one with 20% RAP without a recycling agent. Additionally, two mixtures with RAP contents of 40% and 70% were prepared and tested, incorporating a measured quantity of bio-oil additive to rejuvenate the RAP-aged asphalt binder. Superpave Indirect Tensile (IDT) testing procedures were employed to comprehensively investigate the influences of RAP and the bio-oil additive on fracture behavior. Rheological investigations, specifically Multiple Stress Creep Recovery (MSCR), ensured that the additive's presence did not compromise the blend's response to high temperatures. The results demonstrate the effectiveness of the bio-oil additive in reactivating aged bitumen in RAP, maintaining comparable fracture behavior to the reference mixture while preserving resistance to permanent deformations at elevated temperatures. Careful consideration of additive dosage is emphasized for optimal performance.
