Effect of thermo-oxidative ageing on the rheological properties of bituminous binders and mixes: Experimental study and multi-scale modeling

Abstract

The multiscale modeling of the complex modulus and phase angle of aged hot and warm mix asphalt (HMA and WMA) and bituminous mortar AC02 is investigated in this study. Four thermo-oxidative ageing durations (0, 3, 6 and 9 days) are considered to investigate the long-term thermo-oxidative ageing based on a RILEM ageing procedure. The binders of the aged mixes are extracted and characterized. Moreover, RTFOT and PAV tests are carried out on fresh bitumen to simulate the long-term thermo-oxidative ageing of HMA and WMA. Rheological tests are performed at different temperatures and frequencies to determine the stiffness moduli of binders and mixes that are subsequently curve-fitted with the modified 2S2P1D model. The results show that the stiffness moduli of binders and mixes increase with the long-term thermo-oxidative ageing duration. This increase is more pronounced for WMA and their binders than HMA, this is probably due to the higher water content (5.5%) used for this type of mixture. Moreover, the increase of the stiffness modulus is shown to be related to parameters such as asphaltene content, carbonyl and sulfoxide indices. Finally, a multi-scale model which combines the Mori–Tanaka scheme at mastic and mortar scales and the self-consistent scheme at the mixture scale with possible grain–grain contact between the coarse aggregates, is implemented. It is able to account the evolution of the master curves of the stiffness moduli |E∗| and the phase angles δ of the mixes based on bitumens’ and aggregates’ properties. The reliability of this multi-scale model is assessed through a comparison with experimental data, over a wide range of frequencies and temperatures.