Laboratory Tests and Numerical Simulations of Mixing Superheated Virgin Aggregate with Reclaimed Asphalt Pavement Materials

The use of reclaimed asphalt pavement (RAP) in asphalt mix contributes to sustainable construction. However, a high percentage of RAP in asphalt mix causes concern about compromising the performance of asphalt pavement, especially cracking. The binder transfer and blending between RAP and virgin aggregate during production in an asphalt plant is a critical procedure that affects the performance of the asphalt mix. The heating of RAP by superheated virgin aggregate and the transfer of RAP binder can affect the degree to which virgin binder and RAP binder are blended and thus affect the performance of mixes containing RAP. Several parameters, such as RAP percentage, mixing time, and RAP moisture content, can affect the heating of RAP and the degree of blending between the virgin binder and RAP binder. To increase the understanding of RAP heating and RAP binder transfer, laboratory tests and numerical simulations that employed the discrete element method (DEM) were conducted for this study to investigate the temperature evolution and amount of RAP binder transfer during the mixing of superheated virgin aggregate and RAP materials in a laboratory drum mixer. The results indicated that a longer mixing time or higher superheated virgin aggregate temperature was needed for cases with a high RAP content and high RAP moisture content. The DEM simulations were found to be a promising method for studying the mixing process of superheated virgin aggregate blended with RAP materials. In the future, such DEM simulations could be applied to guide the mix production process for RAP mixes.