Investigation of the mechanical performance of high-RAP WMA mixtures incorporating sasobit and bio-oil rejuvenators

Abstract

The asphalt pavement industry increasingly emphasizes sustainable practices to reduce environmental impacts and promote efficient resource utilization. This study investigates the combined effects of Warm Mix Asphalt (WMA) technology and high reclaimed asphalt pavement (RAP) contents on the mechanical performance of asphalt mixtures, focusing on low-temperature cracking and fatigue resistance. Seventeen mixtures were evaluated, incorporating RAP at 0 %, 25 %, 50 %, and 75 %, with Sasobit added at 3 % by binder weight and a bio-oil-based rejuvenator (BOB) introduced at dosages of 2.5 %, 6 %, and 10 % of RAP binder content. Experimental analyses included rotational viscosity measurements, Semi-Circular Bending (SCB) tests at −12 °C, and incremental repeated load permanent deformation (iRLPD) tests at 25 °C. Results showed that increasing RAP content progressively reduced fracture energy, with an approximate 15–25 % decrease per 25 % RAP increment. The 75 % RAP mixture exhibited a 65 % reduction in fracture energy compared to the virgin control. The 50 % RAP mixture with 3 % Sasobit and 6 % BOB provided the most favorable balance, achieving fracture toughness of 0.966 MPa·m^0.5 and fracture energy of 512.72 J/m², and improving fatigue resistance by 60 % relative to its non-rejuvenated counterpart. Over-dosage of BOB (10 %) destabilized the binder system and reduced performance. ANOVA identified RAP as the dominant factor for energy-based indices and fatigue, with Sasobit and BOB exerting mixture-specific effects, particularly on toughness. Regression analysis showed strong correlations between SCB-derived parameters and iRLPD fatigue index within the tested dataset; a degree-2 polynomial achieved R² ≈ 0.998, but these relationships were mixture-dependent and require validation before broader use. Overall, optimized additive strategies (3 % Sasobit + 6 % BOB) enable balanced performance at 50 % RAP, while 75 % RAP mixtures remained the most susceptible to fracture and fatigue.