Discrete element modeling of asphalt concrete - Microfabric approach

Micromechanical modeling has tremendous potential benefits in the field of asphalt technology for reducing or eliminating costly tests to characterize asphalt-aggregate mixtures for the design and control of flexible pavement structures and materials. In time, these models could provide a crucial missing link for the development of true performance-related specifications for hot-mix asphalt. A microfabric discrete element modeling (MDEM) approach is presented for modeling asphalt concrete microstructure. The technique is a straightforward extension of a traditional discrete element modeling (DEM) analysis, in which various material phases (e.g., aggregates, mastic) are modeled with clusters of very small, discrete elements. The MDEM approach has an the benefits of traditional DEM (e.g., the ability to handle complex, changing contact geometries and the suitability for modeling large displacements and crack propagation). These models also allow for the simulation of specimen assembly (e.g., laboratory compaction of the asphalt mixture). By modeling inclusions such as aggregates with a "mesh" of small, discrete elements, it is also possible for one to model complex aggregate shapes and the propagation of cracks around or through aggregates during a strength test. A commercially available DEM package was used to demonstrate the usefulness of the MDEM approach. A method was also presented to obtain the properties of the matrix material in an asphalt mixture, which is typically difficult to determine experimentally. This study was limited to two-dimensional analysis techniques and involved the simulation of small test specimens. Followup studies involving larger specimen models and three-dimensional modeling capabilities are under way.