Rheological behavior of cold recycled asphalt materials with different contents of recycled asphalt pavements

In Québec, for more than 20 years, cold in-place recycling (CIR) and full-depth reclamation (FDR) have been reliable rehabilitation techniques; restoring pavement condition at an affordable cost with a lower footprint on the environment. Experience reveals that CIR and FDR interventions effectively address the issues of reflective cracking and respect Québec’s Ministry of transportation rutting threshold values. However, despite their commendable performance in the field, the cold recycled emulsified asphalt materials (CRM) has yet to be adequately characterized with respect to their rheological properties. This study was undertaken to evaluate the rheological behavior of the CRM with four different combinations of RAP (50, 75, 85, and 100%). The scope of work for this study consisted of preparing the laboratory compacted CRM specimens, determining the complex modulus (E*) of compacted specimens at various testing temperatures and loading frequencies, analyzing the experimental data with the help of 2S2P1D (2S: two springs, 2P: two parabolic elements, 1D: one dashpot) model and finally, validating the results with pavement design. It was concluded that 100% RAP mixture exhibits extremely high stiffness value at high frequency and low temperature. The results revealed that all four mixtures respect the time–temperature superposition principle with respect to the complex modulus. From a pavement design perspective, the moduli measured in this study do have a big impact. However, since different pavement structure are achieved with those different materials, the stiffest material, the CIR, ended up giving the least performant structure.