Physical characteristics of base binder.

Composite asphalt binder has emerged as a potential solution for improving asphalt functionality at a wide spectrum of temperatures. Storage stability of modified binder remains a main concern to ensure homogeneity during various stages including its storage, pumping, transportation, and construction. The aim of this study was to assess the storage stability of composite asphalt binders fabricated using non-tire waste ethylene-propylene-diene-monomer (EPDM) rubber and waste plastic pyrolytic oil (PPO). The influence of addition of a crosslinking additive (sulfur) was also investigated. Two different approaches were employed in the fabrication of composite rubberized binders: (1) sequential introduction of PPO and rubber granules, and (2) inclusion of rubber granules pre-swelled with PPO at 90°C to the conventional binder. Based on the modified binder fabrication approaches and the addition of sulfur, four categories of modified binders were prepared, namely sequential (SA), sequential with sulfur (SA-S), pre-swelled (PA), and pre-swelled with sulfur (PA-S). For variable modifier dosages (EPDM:16%, PPO: 2, 4, 6, and 8%, and sulfur: 0.3%), a total of 17 combinations of rubberized asphalt were subjected to two durations of thermal storage (48 and 96 hours) and then characterized for their storage stability performance through various separation indices (SIs) based on conventional, chemical, microstructural, and rheological analyses. The optimal storage stability performance was achieved at a PPO dosage of 6% under the four candidate approaches. It was also observed that the SIs based on chemical analysis and rubber extraction test had a good correlation with rheology-based SIs compared to the conventionally used softening point difference. A composite modified binder with PPO and EPDM rubber having adequate storage stability is a promising step in the use of sustainable composite-modified binders in asphalt pavement construction.复合沥青胶结料（Composite asphalt binder）已成为实现宽温度区间内沥青路用性能优化的潜在解决方案。改性沥青胶结料的储存稳定性仍是保障其在储存、泵送、运输及施工等全流程中均匀性的核心关切。本研究旨在评估采用非轮胎废弃三元乙丙橡胶（ethylene-propylene-diene-monomer, EPDM）与废弃塑料热解油（waste plastic pyrolytic oil, PPO）制备的复合沥青胶结料的储存稳定性，并考察了交联添加剂（硫磺）的掺加影响。制备复合橡胶改性沥青胶结料时采用了两种不同工艺：（1）先掺加PPO再掺入橡胶颗粒的分步添加法；（2）将经90℃下PPO预溶胀的橡胶颗粒掺入常规沥青胶结料的预溶胀法。基于上述改性工艺及硫磺掺加方案，共制备得到四类改性沥青胶结料，分别为分步添加组（SA）、分步添加+硫磺组（SA-S）、预溶胀组（PA）以及预溶胀+硫磺组（PA-S）。针对可变掺量的改性剂（EPDM掺量为16%，PPO掺量设为2%、4%、6%、8%，硫磺掺量为0.3%），本研究共制备17组橡胶沥青试样，分别经受48小时与96小时两段热养护时长，随后通过基于常规试验、化学分析、微观结构分析及流变学分析的多种离析指标（separation indices, SIs）对其储存稳定性性能进行表征。在四类制备工艺下，当PPO掺量为6%时，试样可获得最优的储存稳定性表现。研究同时发现，相较于常规采用的软化点差指标，基于化学分析与橡胶萃取试验得到的离析指标与基于流变学的离析指标具有更优的相关性。具备优异储存稳定性的PPO与EPDM复合改性沥青胶结料，为可持续复合改性胶结料应用于沥青路面施工提供了极具前景的技术路径。