Performance of Waste Expanded Polystyrene as Bitumen Modifier: A Comparative Assessment with Virgin Bitumen

This study explores the feasibility of using waste expanded polystyrene (WEPS) as a bitumen modifier for road pavement. WEPS was blended with VG-10 and VG-30 bitumen (0–6 wt%) using the wet process to produce WEPS-modified bitumen (WPMB). Improvements were observed in softening point, viscosity, and thermal properties, while a decline in penetration values limited WEPS addition to 5 wt% for VG-30 grade bitumen. VG-30-based WPMBs exhibited superior physical and rheological properties. FTIR confirmed physical dispersion without chemical reaction, while FESEM indicated strong compatibility and storage stability. WPMBs showed enhanced thermal stability, higher complex shear modulus, and lower phase angle, indicating improved elasticity and deformation resistance. The V30P5 sample demonstrated up to 28.20 times higher percent recovery and over 90% reduction in non-recoverable creep compliance compared to VG-30. Additionally, the rutting parameter improved significantly. Overall, VG-30-based WPMBs with up to 5% WEPS show strong potential for sustainable road construction.