Influence of thermal oxidative aging on temperature induced self-healing transition of polymer modified bitumens

In this study, the fatigue-healing-fatigue (FHF) test is conducted to investigate influence pattern of temperature and thermal oxidative aging on the self-healing ability of styrene-butadiene-styrene (SBS) modified bitumen (SBS-MB) and polyethylene (PE) modified bitumen (PE-MB). Results display that the optimum healing temperature (OHT) of each bitumen (wherever unaged or aged) is in the phase transition (PT) zone, and is lower than softening point, followed by its Newtonian flow temperature. Two types of healing crossover temperature points are found in the healing-temperature curves of polymer modified bitumen (PMB) samples with various aging degrees, indicating the complexity of self-healing transition phenomenon in the aged PMB samples. Hence, the evaluation of aging effects on the self-healing ability of PMBs should be performed in a wide temperature range. Furthermore, the self-healing ability of PMBs is gradually weakened with the deepening of aging extents. Notably, the thermal oxidative aging imparts totally different effects to the self-healing ability of SBS-MB and PE MB at lower temperatures. Moreover, the results of softening point test, fluorescence microscopy test, frequency sweep test and differential scanning calorimeter test convey that the altered phase structure and polymer distribution of PMBs during aging elicit the healing-temperature curves shift and self-healing transition. (C) 2020 The Authors. Published by Elsevier Ltd.