Thermal Equilibrium Process When Mixing Asphalt with Reclaimed Asphalt Pavement: Experimental Investigation and Simulation

Abstract

The thermal equilibrium of asphalt mixtures, when combined with reclaimed asphalt pavement (RAP), forms the foundation for high-quality hot pavement recycling. This study focuses on quantifying the thermal equilibrium process of recycled asphalt during mixing. To achieve this objective, a typical RAP content of 20% was utilized in preparing the recycled asphalt. In the experiments, three preheated RAP temperatures were considered to reflect different practical scenarios. Thermal images of recycled asphalt were captured throughout the entire mixing process from 10 s to 90 s in order to characterize the temperature evolution pattern of recycled asphalt mixtures. In addition to experiments, discrete element simulation was conducted to elucidate additional details regarding temperature exchange. The results indicated that the initial thermal equilibrium during mixing may have a significant impact on RAP dispersion and temperature variation, while the subsequent mixing period has limited influence on the final thermal state. Furthermore, it is observed that complete thermal equilibrium cannot be achieved due to the nonuniform distribution of RAP at the end of mixing. In addition, a model describing the temperature evolution of RAP is proposed in this study, which demonstrates a good fit with the data.