Performance enhancement of bitumen using char from co-pyrolysis of groundnut shell and plastic waste

This study presents a comprehensive evaluation of VG30 bitumen modified with char derived from the co-pyrolysis of groundnut shells (GS) and plastic wastes, including high-density polyethylene, low-density polyethylene, and polypropylene. Char-modified bitumen samples were prepared with incremental char dosages ranging 3% to 15% by weight, and systematically assessed for their physical, mechanical, and chemical properties in accordance with relevant Indian Standards. The results revealed a consistent decline in specific gravity across all series—from 0.980 to 0. 0.9640. Penetration values decreased from 46 to 31 (0.1 mm), signifying enhanced stiffness, while ductility reduced from 104 cm to 35 cm for HDPE induced biochar. Softening point improved significantly, reaching up to 67.25 °C for GS + HDPE-modified binders at 15%, approaching VG40 (50 °C) performance. Absolute viscosity at 60 °C increased from 3087.86 Poise (control) to 6147.15 Poise, while kinematic viscosity at 135 °C rose from 380 cSt to 706.02 cSt, confirming superior high-temperature resistance and deformation stability. FTIR spectroscopy identified notable interactions between char functional groups and the bitumen matrix, particularly in GS + HDPE composites, suggesting chemical compatibility. Phase separation analysis demonstrated excellent storage stability up to 12% char content. ANOVA results confirmed that both char type and dosage significantly influenced viscosity and softening point, with GS + HDPE identified as the most effective blend. Furthermore, Marshall stability tests on DBM Grade II mixes with optimized char blends showed superior load-bearing and flow characteristics. Overall, the study demonstrates the improved performance of bitumen modified with co-pyrolyzed agro-plastic char, promoting viable infrastructure through the valorization of agricultural and plastic wastes.