Effect of microwave pretreatment on characteristics of asphalt binders modified with scrap non-tire automotive rubber and waste derived pyrolytic oils after prolonged thermal storage

Abstract

The use of waste automotive rubber and pyrolytic products has recently gained interest in asphalt binder modification, and it also presents an appealing solution towards waste re-utilization and sustainable asphalt binder modification. Further, composite modification of asphalt binders is now often attempted to achieve a wider range of benefits in the asphalt binder performance through the modifiers. For the petroleum crude-based asphalt binders after their modification with different additives, viz. polymers, rubbers, and oils, the phase separation behavior, usually assessed in terms of storage stability, plays a very important and crucial role in its long-term performance. A modified asphalt binder must possess adequate storage stability to assure homogeneity during storage and hauling at elevated temperatures to achieve the desired performance after construction. The present study firstly evaluated the long-term phase separation behavior/storage stability of asphalt binders modified with waste non-tire rubber granules (ethylene-propylene-diene monomer (EPDM) type) alone and then for composite rubberized asphalt binders formulated with EPDM rubber along with tire pyrolytic oil (TPO) and plastic pyrolytic oil (PPO) after microwave pretreatment. To assess the standard and the long-term phase separation behavior in terms of storage stability, formulated rubberized asphalt binders were subjected to thermal storage at two different scenarios: (a) for 2 and 4 days at163 °C, and (b) for 2, 4, 7, 10, and 14 days at 135 °C. The phase separation behavior and performance of rubberized asphalts post long-term storage were evaluated in terms of chemo-rheological, microstructural, and rubber dissolution tests. A total of 28 asphalt binders with variable modification and thermal storage periods were characterized and evaluated. Both storage temperature and duration were found to play a critical role in dictating the storage stability and chemo-rheological performance of the rubberized asphalts, and the prolonged storage stability of rubberized binders correlates well with their rutting and fatigue performance. The pretreatment of rubber granules with pyrolysis oils using microwave irradiation facilitated the achievement of a composite modified asphalt binder with good storage stability and rheological performance.