Evaluating the elastic recoverability of bitumen during ageing process

This study systematically evaluated the elastic recoverability of bitumen during laboratory ageing processes. Two types of unmodified (neat) bitumen and one type of SBS polymer modified bitumen (PMB) were employed in this study. The monotonic elastic recovery measured by a DSR at a consistent shear rate of 2.315 s-1, the binder yield energy, and the multiple stress creep and recovery (MSCR) tests were carried out. Based on the results, it was seen that the elastic recoverability of neat bitumen increased continuously with ageing degrees, while it increased then decreased for PMB due to the simultaneous physical hardening and polymer degradation. Different testing methods generally showed consistent trends and strong correlations. The MSCR test was identified to be inappropriate for characterising the elastic recoverability of PMB, as the nine-second recovery period was insufficient for PMB to fully recover.