Optimizing SBS & Tire Pyro Oil Modified VG 30 Bitumen for Sustainable Pavements

In recent years, Indian roads have experienced a significant increase in axle load and traffic volume, necessitating improved performance in top bituminous layers. While Indian guidelines recommend VG40 grade bitumen for perpetual pavements, its limited supply prompts widespread use of VG30 grade bitumen. This study explores the viability of modified VG30 bitumen, employing Styrene Butadiene Styrene (SBS) and Tire pyro oil (TPO) as modifiers, as an alternative to VG40. Rheological tests, including Dynamic Shear Rheometer and Brookfield Viscometer, alongside morphological and chemical analyses, ascertain the optimal SBS dosage. Addition of TPO, ranging from 1% to 3%, reduces mixing and compaction temperatures. Marshall Stability and Indirect Tensile Strength tests compare strength characteristics. Sixteen perpetual pavement sections are designed based on Indian guidelines, comparing thickness, life cycle cost, and carbon dioxide emissions over five decades. Modified VG30 binder exhibits only a slight increase in thickness compared to unmodified VG40 binder, while significantly reducing life cycle costs and carbon dioxide emissions. Experimental results suggest that modified VG30 with 3% SBS, and optionally with 1% TPO, can effectively replace VG40 grade bitumen for perpetual pavements to address its supply issue.