Abstract: The use of high contents of Reclaimed Asphalt Pavement (RAP) in bituminous mixtures poses significant challenges related to permanent deformation and long-term mixture stability. This study evaluates the mechanical response of asphalt mixtures containing 80% RAP subjected to accelerated traffic loading using a Circular Road Simulator (CRS), combined with high-resolution 3D surface scanning and a fractional viscoelastic model. Three AC16S mixtures are analysed: a reference mixture with B50/70 binder, a mixture with 80% RAP and PMB 45/80-65 binder, and a mixture with 80% RAP and an experimental binder (PMB3). Surface deformation is quantified from height variations measured in two regions of interest: R1, corresponding to the direct tire-pavement contact zone, and R2, an adjacent laterally confined region, for loading states up to 500,000 cycles. Experimental results show that the reference mixture exhibits unstable deformation patterns with pronounced rutting, reaching experimental strains of up to 0.22 in R1 and ?0.20 in R2 at 500,000 cycles. In contrast, RAP mixtures display significantly reduced deformation, with strains generally below ±0.05 for most loading states. The PMB3 mixture shows the most favourable behaviour, combining minimal permanent deformation, controlled transitions between rutting and surface uplift, and limited surface height variation, with -Z values typically below 1 mm in both regions. The fractional viscoelastic model shows good agreement with the experimental deformation for the analysed mixtures and loading states, indicating its capability to represent the observed viscoelastic response within the analysed conditions, with relatively low errors in most cases. The identified parameters reveal that RAP mixtures, particularly the PMB3 mixture, exhibit higher stability in stiffness, viscosity, and fractional orders, confirming improved resistance to creep and enhanced recovery capacity. These results demonstrate that the proposed combined experimental-modelling approach provides a coherent framework for describing the viscoelastic performance of high-RAP asphalt mixtures under controlled test conditions representative of realistic loading conditions.
