Case study: Dynamic modulus characterization of naturally occurring bituminous sands for sustainable pavement applications

Oil sand is a generic name given to naturally occurring deposits of ituminous sand materials that are mined for crude oil production. These materials are currently used as subgrade materials of emporary and permanent roads in oil sand fields. The presence of high bitumen content makes oil sand materials problematic for field operations of off-road haul trucks and shovels during the warm spring and summer months. The behavior of oil sand materials is primarily dependent upon stress states, temperature, and the rate of loading or frequency. To effectively account for temperature and loading frequency, dynamic modulus is the preferred material property to characterize bituminous materials. In this paper, dynamic modulus is determined for three types of oil sand materials with natural bitumen contents of 8.5, 13.3, and 14.5% by weight using cyclic load triaxial test procedure. All the three oil sand samples were compacted close-to-field densities and then tested at two temperatures and three loading frequencies (related to field trafficking speeds) at different stress states. Based on the test results, dynamic modulus was modeled as a power function of the applied stress states and temperature. Using all the test data obtained from the three oil sand samples, unified dynamic modulus characterization models were successfully developed to account for stress state, bitumen content, and temperature. The proposed model can be calibrated for field practical use to estimate modulus and deformation behavior of these oil sand materials for their sustainable use in pavement applications.