Development of Performance-Based Blending Charts for Recycled Binder Blends

This study explores the development of performance-based blending charts for recycled binder blends, considering the rutting and fatigue resistance of recycled binder blends. For developing the blending chart, the nonrecoverable creep compliance $J_{nr}$ evaluated in the multiple stress creep recovery (MSCR) test and the bitumen fatigue performance parameter $N_f$ estimated from the linear amplitude sweep (LAS) test were utilized. These parameters are recognized for their superior representation of rutting and fatigue performance. Blending charts were initially developed separately for $J_{nr}$ and $N_f$, then combined to create a performance-based blending chart that illustrates how $J_{nr}$ and $N_f$ change with reclaimed asphalt binder in total binder ($R/T$). The study demonstrates the aforementioned concept for a laboratory-synthesized reclaimed asphalt pavement (RAP) binder when blended separately with two virgin binders (viscosity grades VG10 and VG20). Because viscosity grade VG40 binder is recommended for wearing-course and binder-course mixes for high-volume roads in India, the RAP blends were synthesized targeting the $J_{nr}$ and $N_f$ values estimated for VG40 binder at 60°C and 25°C, respectively. The performance-based blending charts identify an $R/T$ range where the blend outperforms the target binder in both rutting and fatigue performance. The study revealed that when the softer virgin binder (VG10) was used to rejuvenate RAP properties, the desired $R/T$ range was broader compared with VG20. As the strain level increased from 2.5% to 5%, the desired $R/T$ range narrowed, indicating that the $R/T$ range was influenced by both the type of soft binder and the strain level in the LAS test. This also implied that higher RAP incorporation is advisable in the case of thick pavements when compared with thin layers.