Influence of RAP addition on linear viscoelastic behaviour and low-temperature performance of hot mix asphalt

Quebec Ministry of transportation currently limits the use of reclaimed asphalt pavement (RAP) materials to 10% in surface courses, due to the potential risks associated with cold weather. This restriction hinders the adoption of high RAP content mixes (>10%), which are nevertheless beneficial for reducing the carbon footprints of the asphalt materials sector and designing more environmentally and sustainable pavements. A study was therefore carried out to optimize the formulation and performance of high-RAP asphalt mixes in cold climates. The study evaluates the linear viscoelastic (LVE) behaviour using the complex modulus test and low-temperature performance (thermal stress restrained specimen test (TSRST)) of an Enrobé Semi-Grenu 10 mm (ESG10) mix with RAP contents ranging from 0% to 100%, using a PG 52S-34 binder. Complex modulus tests were fitted to the 2S2P1D model. TSRST tests measured cold performance. The results show that above 20%, stiffness increases and modifies the E2/E1 (viscous modulus (E2) and elastic modulus (E1)) ratio. Up to 30%, the addition of RAP does not significantly affect thermal performance or LVE behaviour.