Evaluating Storage Stability and Performance Characteristics of Recycled Composite Plastic Modified Asphalt Binders

This study evaluated the storage stability and performance of composite plastic modified binders at 1-3% dosages using polyethylene grafted maleic anhydride (PE-g-MA) and reactive elastomeric terpolymer (RET) stabilizers. Thermal characterization using differential scanning calorimetry (DSC) showed melting points of 130-155°C, suitable for wet blending. Storage stability was evaluated using complex shear modulus separation index (SI) and fluorescence microscopy (FM). Both stabilizers improved stability up to 2%, but RET achieved more uniform and homogeneous plastic dispersion in asphalt binder matrix. Rheological properties were evaluated through Superpave performance grading (PG), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS). Composite plastic alone raised the high PG by up to one grade, and RET added a further two grades, producing three grades for HDPE + PP (HP) and two for LDPE + HDPE + PP (LHP), while PE-g-MA had minimal effect on high PG. Both stabilizers maintained base-binder low PG, with RET providing greater improvement. RET significantly improved rutting by enhancing recovery and lowering Jnr, outperforming PE-g-MA. Plastic degraded fatigue performance, but stabilizers mitigated this; RET and PE-g-MA improved fatigue life by approximately 1,500% and 270%, respectively. The RET 2% binder without plastic showed the highest recovery, lowest Jnr, and longest fatigue life among modified binders, indicating RET is the principal performance determinant, while composite plastic provides recycled supplementary high-temperature stiffening within the RET-stabilized matrix. Overall, RET was more effective than PE-g-MA. Thus, composite plastic modified binders with up to 2% dosage with stabilizers can offer better storage stability and performance for sustainable pavement applications.