In the context of the circular economy, the use of recycled asphalt in road construction has become a strong necessity. The incorporation of reclaimed asphalt pavement (RAP) in asphalt mixes has been given a new boost by the directives of the last years until the pact of commitment of the mobility infrastructure actors, signed in January 2021. Thus, the objective of the thesis is to understand the influence of RAP material on the durability of pavements. The originality lies in the investigation of the remobilization of the aged binder and the homogeneity of the mixture with the fresh binder by numerical and experimental laboratory/site studies. Considering that this mixing between aged and fresh binders is done at the mortar or intergranular mastic scale, a multi-scale approach was used. Laboratory tests are carried out on these different scales (bitumen, mastic, mortar and asphalt) for fresh and aged materials and their mixtures to determine their mechanical performances. In the numerical field, a quadri-phase heterogeneous model is developed based on the finite element method and geometry generation software developed in our laboratory. By comparing the modulus of the digital mix with the modulus of a mix mortar tested in the laboratory, the mix experimental degree of blending DOB was predicted. Both tri-phase and quadri-phase models have successfully predicted the DOB of a mortar. This study is completed by full-scale tests. A base course made of an HMA material called GBƐ+, a high-performance material containing 40% RAP, is placed in an experimental pit in our laboratory. This layer is loaded by the Mobile Load Simulator MLS10 which is used to simulate accelerated traffic on a pavement structure. The latter is instrumented with sensors in order to monitor its response and thus to evaluate its life span on a real scale. Damage calculation and FWD measurements showed that this material survived relatively well under severe traffic and temperature conditions.