Rheological Modelling of the Bitumen from Reclaimed Asphalt with Rejuvenation and Re-ageing

Abstract

Hot recycling of reclaimed asphalt (RA) in new asphalt concrete (AC) allows achieving large environmental and economic benefits. However, the aged bitumen in RA has a stiff and brittle behaviour, which may lead the AC to premature fatigue, thermal and reflection cracking. In the last years, many researches aimed at studying the effect of ageing on bitumen rheological properties to model the mechanical behaviour of RA. However, how these properties changes in the AC including hot-recycled RA and rejuvenator during its service life is still an object of investigation. The present paper aims at analysing the evolution of the rheological behaviour of the bitumen extracted from RA with rejuvenation (40/60 blending of virgin and RA bitumen, with addition of a rejuvenator) and re-ageing (simulating the service life of the hot recycled AC). RTFOT and PAV devices were used to reproduce bitumen ageing in the laboratory and DSR allowed determining the complex modulus of the binders. The ageing and rejuvenating effects were characterised through the variation of the 2S2P1D model parameters and apparent molecular weight distribution (AMWD). Results proved the efficacy of the rejuvenation process in reducing stiffness and raising the viscous properties of the RA bitumen. After long-term re-ageing (RTFOT + PAV), the rejuvenated RA bitumen showed comparable rheological behaviour with respect to the bitumen initially recovered from RA. However, AMWD analysis showed that the rejuvenator did not adequately disrupt the asphaltene clusters in the aged bitumen.