Numerical investigation of dry and wet mixing processes of asphalt mixtures containing reclaimed asphalt pavement
This study proposes a novel simulation technique to study the dry and wet mixing processes of asphalt mixtures containing reclaimed asphalt pavement (RAP). The simulations were done using the discrete element method (DEM) framework with integrated models of heat transfer, moisture drying and transfer, and asphalt binder coating and transfer. Laboratory experiments and numerical simulations were conducted to determine the effects of RAP percentage and moisture content on the temperature evolutions of virgin aggregates and RAP materials during the dry mixing process. Optimal dry and wet mixing times are recommended based on the developed numerical models and the simulated pugmill. Longer dry mixing time is needed for mixtures containing higher percentages of RAP, especially at higher mix discharge temperatures. The optimal wet mixing time based on the simulated pugmill was determined to be between 28 and 30 seconds, regardless of RAP percentages. The study shows that the proposed numerical simulation framework with integrated models of heat transfer and moisture drying are useful to quantify the effects of RAP percentage and RAP moisture content on the temperature evolution of the mixing system. This is promising as a guide to the production of asphalt mixtures containing RAP materials.
Keywords: discrete element method, heat transfer, moisture drying and transfer, asphalt coating, reclaimed asphalt pavement