The impact of utilizing recycled EPDM both independently and in conjunction with SBS on the overall characteristics of bitumen

Abstract

The rising demand for raw materials and the environmental burden of industrial waste have increased interest in sustainable solutions for asphalt pavement engineering. Recycled ethylene-propylene-diene monomer (EPDM) is a promising modifier that combines thermoplastic resilience with environmental benefits. This study investigates the modification of a 70/100 penetration grade bitumen with EPDM and its co-modification with styrene-butadiene-styrene (SBS). A comprehensive experimental program evaluated conventional properties, rheological behavior, aging resistance, thermal susceptibility, elastic recovery, and microstructural features. Results indicated that EPDM improved softening point by 3-5% and increased viscosity, though it also heightened susceptibility to phase separation. Co-modification with SBS provided more pronounced improvements: high-temperature stiffness (G*/sin delta) rose by up to 25% compared to SBS-only modification, non-recoverable creep compliance decreased by more than 70%, and elastic recovery increased by up to 130%. FTIR analysis further showed about 70% lower oxidation indices in co-modified binders, while BBR testing confirmed that all formulations retained satisfactory low-temperature performance (PG 70-16). Overall, the 10% EPDM + 2% SBS binder achieved the most balanced performance across rutting resistance, elasticity, and oxidative durability.