Effect of Ageing Kinetics on the Rheological Properties of Bituminous Binders and Mixes: Experimental Study and Multi-scale Modeling

The oxidative ageing of hot mix asphalt (HMA) and foamed warm mix asphalt (WMA), performed through laboratory accelerated ageing processes is investigated in this study. 50/70 pen-grade bitumen was used to produce the mixes. Four ageing durations (0, 3, 6 and 9 days) were considered to investigate the kinetics of long-term ageing based on a RILEM ageing procedure. The binders of the aged mixes were extracted and characterized. Moreover, RTFOT and PAV tests were carried out on fresh bitumen to simulate the long-term ageing of HMA. These procedures were adapted to simulate the long-term ageing of WMA for which no standardized ageing procedure exist. Rheological tests were performed to determine the stiffness modulus of binders and mixes. The results show that the stiffness modulus increases with the ageing kinetic for both binders and mixes. This increase is more pronounced for WMA and their binders than HMA. Furthermore, the equivalence between the RTFOT and RTFOT + PAV ageing procedures performed on bitumen and the RILEM procedure carried out on loose mixes was discussed for both HMA and WMA. Finally, a multi-scale model was implemented to predict stiffness moduli and phase angles of the mixes based on bitumens’ and aggregates’ properties. The results show a relatively good agreement between the multi-scale model and the experimental data curve-fitted with the well-known modified Huet-Sayegh model.