This study evaluates the performance and aging resistance of high-dosage crumb rubber modified bitumen (CRMB) by analyzing physical and rheological properties of viscosity grade-30 (VG-30) binder modified with 0%, 10%, 15%, 20%, and 24% crumb rubber (CR) before and after short-term aging. Conventional tests (Penetration, softening point, storage stability) and rheological tests (complex modulus, phase angle, rutting factor, elastic recovery using dynamic shear rheometer (ER-DSR), multiple stress creep recovery (MSCR), frequency sweep and zero shear viscosity (ZSV)) were carried out. Elastic recovery improved with increasing CR content and showed strong correlation (R² = 0.79) and (R² = 0.96) with percent recovery obtained from MSCR test for unaged and short-term aged CRMB respectively. Aging index (AI) based on complex modulus decreased 1.85 (VG-30) to 1.03 (24% CR) at 60°C, while ZSV-based AI showed substantial reduction, from 3.22 (VG-30) to 1.44 (24% CR), indicating improved durability and resistance to oxidative aging. The ZSV increased with CR content, indicating improved resistance to permanent deformation due to stronger internal network formation. The relaxation time (λ) reached a maximum at 20% CR with balanced viscoelastic behavior. Accordingly, 20% CR was identified as the optimum rubber content based on ZSV, λ, n, and elastic recovery, since beyond this level further rubber addition does not result in significant improvements in elastic recovery and ZSV. It is concluded from the study that addition of 20% CR in VG-30 binder reduces oxidative aging and improves binder rutting performances, resulting in sustainable and environmentally friendly binder for flexible pavements.
