Properties at Low Temperatures of Asphalt Mixes Containing High Content of Multi-recycled RAP

Abstract The reuse of reclaimed asphalt pavement (RAP) in the production of new asphalt mixes is a valuable environmental approach. Likewise, new lower-temperature manufacturing processes (warm) of asphalt mixes have an impact in the reduced fuel consumption and gas emissions during production. In 2014, the French National Research Agency launched the French national project “Innovation for Materials and Processes for Improving the Multi-Recycling of Mixtures” (IMPROVMURE). The main objective of the IMPROVMURE project was to determine, over the life cycle of pavement materials, the impact of successive recycling at different rates and for different manufacturing techniques (hot and warm processes). To estimate the thermomechanical properties of multi-recycled asphalt mixes, a characterization of behavior by coupling the thermal and mechanical effects at low temperatures was carried out. This paper presents the thermal stress restrained specimen test (TSRST) results of six asphalt mix types, three hot asphalt mixes, and three half-warm asphalt mixes using a foamed binder. Some of these asphalt mixes were manufactured with a content up to 70 % RAP and 70 % multi-recycled RAP. TSRST were performed on cylindrical specimens at the University of Lyon/école nationale des travaux publics de l’état (ENTPE). The failure temperature (TF), failure stress (σF), and failure radial deformation (εrF) were evaluated to analyze and compare the behavior of mixes at low temperature. The influences of RAP content, recycling cycle, air void content, and manufacturing process were studied, and the air void content showed an effect inversely proportional to the failure stress.