Modeling of Hot-Mix Asphalt Compaction: A Thermodynamics-Based Compressible Viscoelastic Model

Compaction is the process of reducing the volume of hot-mix asphalt (HMA) by the application of external forces. As a result of compaction, the volume of air voids decreases, aggregate interlock increases, and interparticle friction increases. The quality of field compaction of HMA is one of the most important elements influencing asphalt pavement performance. Poor compaction has been associated with asphalt bleeding in hot weather, moisture damage, excessive aging and associated cracking, and premature permanent deformation. This study was conducted to develop a model within the context of a thermomechanical framework for the compaction of asphalt mixtures. The asphalt mixture was modeled as a nonlinear compressible material exhibiting time-dependent properties. A numerical scheme based on finite elements was employed to solve the equations governing compaction mechanisms. The material model was implemented in the Computer Aided Pavement Analysis (CAPA-3D) finite-element (FE) package. Due to the difficulty of conducting tests on the mixture at the compaction temperature, a procedure was developed to determine the model’s parameters from the analysis of the Superpave® gyratory compaction curves. A number of mixtures were compacted in the Superpave® gyratory compactor using an angle of 1.25 degrees in order to determine the model’s parameters. Consequently, the model was used to predict the compaction curves of mixtures compacted using a 2-degree angle of gyration. The model compared reasonably well with the compaction curves. FE simulations of the compaction of several pavement sections were conducted in this study. The results demonstrated the potential of the material model to represent asphalt mixture field compaction. The developed model is a useful tool for simulating the compaction of asphalt mixtures under laboratory and field conditions. In addition, it can be used to determine the influence of various material properties and mixture designs on the model’s parameters and mixture compactability.\n