Thermal, rheological, and aging characterization of ethylene vinyl acetate polymer modified asphalt binder

Conventional polymer modification requires high polymer concentrations, posing cost challenges. Thus, exploring alternatives such as composite polymer modification, which utilizes lower polymer concentrations while achieving similar performance levels, is essential. The present study examined the effects of single and composite Ethylene Vinyl Acetate (EVA) polymer modifications on the thermal, rheological, and aging characteristics of binders. The base viscosity binder (VG40) was modified with EVA-18 alone and a combination of EVA-18 and EVA-28 polymers to produce single and composite modified binders, respectively. The rheological properties (complex shear modulus and phase angle), as well as the rutting and fatigue performance these binders were evaluated and compared. Further, correlations between thermal and rheological properties were established, and the aging resistance of modified binders was assessed by conducting Fourier Transform Infrared Spectroscopy (FTIR). Thermal analysis revealed that the binders modified with single polymer displayed a distinctive broad endothermic peak between 73 to 75 °C, marking the melting of EVA polymer’s crystalline structure. In contrast, the binders modified with composite polymers showed no such peaks, likely due to the higher vinyl acetate content in EVA-28. The thermal characteristics of single polymer modified binders showed notable enhancements as the polymer content increased from 3 to 7%. The heat of fusion rose from 0.39 to 1.02 J/g, and crystallinity increased from 4.50 to 5.01%. Good correlations were observed between crystallinity and the rheological properties of binders. Composite polymer modification achieved a 2% reduction in polymer content compared to single polymer modification, maintaining an equivalent ranking based on rutting and fatigue performances. For equivalent polymer content, composite polymer modified binders demonstrated lower levels of polymer degradation at long term aging level (degradation rates of 1.03–1.09) compared to single polymer modified binders (degradation rates of 1.05–1.37). This study is expected to provide valuable insights into binder characteristics, particularly in the realm of EVA modified binders.