Micromechanical modeling of steady-state deformation in asphalt

A micromechanical model for the steady-state deformation of idealized asphalt mixes is presented. Triaxial compression tests were conducted on idealized asphalt mixes and the volumetric and deviatoric strains were measured. The specimens were observed to dilate under compressive stresses and the deformation behavior was seen to be dependent on the hydrostatic as well as the deviatoric stresses. A simple model for the nonlinear viscous steady-state behavior of idealized mixes is presented based on a "shear box" analogy. Predictions of the model are seen to agree well with experimental measurements for a wide range of conditions. An upper bound is calculated for the steady-state deformation rates within a plane strain half space comprising the idealized asphalt mix subject to a uniform pressure over a finite contact strip. The deformation rate varies nonlinearly with the applied load and is strongly dependent on the hydrostatic stress. Further, the deformation rate is seen to be a maximum at a position about half a contact length below the surface of the half space. These findings are in general agreement with wheel tracking experiments on these idealized mixes.