Caractérisation multi-échelle des enrobés bitumineux à chaud contenant des granulats bitumineux recyclés et des bardeaux d’asphalte de post-consommation

Abstract

The use of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) in the formulation of asphalt mixes is a good solution allowing the reuse of non renewable resources. In Quebec, the legislation allows the reuse up to 20% and 3% respectively of RAP and RAS in asphalt mixes for surface layers. According to LC 4202 standard, 100% of the RAP bitumen can be mobilised while for the RAS this percentage is estimated at 25%. The main objective of this thesis is to understand the effects of the combined addition of RAP and RAS on the thermomechanical behaviour of asphalt mixes. The bibliographical research allowed to identify the main axes of study. Several works in the literature disagree about the mobilisation rates proposed by the LC 4202. They highlight that the addition of recycled bituminous materials leads to a stiffer final asphalt, causing a drop in thermal cracking resistance. These findings are mainly related to a blend between the virgin binder the recycled ones. The literature reviews also allowed to identify relevant tools for analysis such as the use of rheological models and multi-scale transition equations. A multi-scale work plan is proposed, it includes binder scale (bitumen and mastic) and asphalt mix scale. First, at binder scale, a conventional, physicochemical and rheological characterization was carried out on the base bitumen and blends between them. Two blending laws were proposed. A linear law for predicting the parameters and characteristics non dependent on temperature, and a logarithmic one for those dependent on temperature. These laws are also validated at the mastic level. The latter, admitted as the real binder in asphalt mixes, allowed to conclude that the stiffening effect noted on the asphalt mix scale is not only caused by the blend between the bitumen but also by the presence of a different mastic compared to that of asphalt mixes without recycled materials. Then, a multi-scale work associating experimentation and the modeling is proposed to study the mobilisation rate. It is based on the rheological characterization at asphalt mix scale and bitumen scale, then the use of the SHStS transformation to go from one scale to another. It validated that the percentage of mobilisation of RAP is 100% and more than 50% for RAS. At asphalt mix scale, the work was performed at different characterization temperatures. At laying temperatures, the addition of RAP and RAS did not show any significant effect on compactibility under the test conditions studied. At service temperatures, as expected, a stiffening following linear evolutions with recycled materials content is noted. At low temperatures, correlations are proposed between the thermal stress restrained specimen test result and the creep modulus results calculated from the complex modulus using rheological models. This method allowed to validate the weaknesses noted in the literature of the mechanical behaviour of the asphalt mixes containing recycled materials in the fragile domain.

Date	28 Jan 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Alan Carter (Supervisor), Anne Dony (Co-supervisor) & Daniel Perraton (Co-supervisor)