Effects of high RAP and babassu oil contents on the mechanical and economic performance of asphalt mixtures

This study investigates the mechanical performance and economic feasibility of asphalt mixtures incorporating high reclaimed asphalt pavement (RAP) contents rejuvenated with babassu oil (BO). Asphalt mixtures were produced with RAP contents ranging from 0% to 70% and BO dosages between 0% and 7%. Mechanical behavior was evaluated through indirect tensile strength (ITS), moisture susceptibility (ITSR), resilient modulus (RM), flow number (FN), fatigue resistance, and Cantabrian abrasion loss. Structural performance was assessed using mechanistic–empirical pavement design with the MeDiNa method, followed by a cost-per-kilometer and net present value analysis. High RAP contents significantly increased mixture stiffness, with ITS and RM rising up to 44.7% and 82.8%, respectively, compared to the control mixture. The incorporation of babassu oil effectively mitigated excessive stiffness and enhanced fatigue performance; mixtures with 56%, 63%, and 70% RAP were all classified as fatigue class 4. Moisture resistance improved with increasing BO content, reaching a 6.1% increase in ITSR for the 70% RAP–7% BO mixture, while abrasion loss results confirmed adequate surface durability. Mechanistic analysis showed that high-RAP mixtures with babassu oil enabled reductions in asphalt layer thickness without compromising pavement performance. From an economic perspective, the 70% RAP–7% BO mixture yielded the lowest production and construction costs, achieving savings of up to 73% per kilometer and the most favorable net present value over a 10-year analysis period. Overall, babassu oil proved effective in enabling very high RAP contents while maintaining or improving mechanical performance and substantially reducing costs, supporting sustainable and economically viable pavement solutions. • RAP contents up to 70% increased stiffness, with ITS and RM gains of up to 44.7% and 82.8%. • Babassu oil reduced excessive stiffness and improved fatigue resistance; all high-RAP mixtures reached fatigue class 4. • Moisture resistance increased by up to 6.1% with higher babassu oil dosage. • Mechanistic design indicated reduced asphalt layer thickness for high-RAP mixtures without performance loss. • The 70% RAP–7% babassu oil mixture achieved up to 73% cost savings per kilometer and the best economic performance. • Babassu oil is a novel bio-based rejuvenator aligned with bioeconomy goals.