Mechanistic Comparison of Cement- and Bituminous-Stabilized Granular Base Systems

The Saskatchewan, Canada, Department of Highways and Transportation is investigating alternative recycling and strengthening systems for inservice thin granular pavements. This research is being performed to improve the granular pavement structural integrity and to reduce the dependence on new source aggregates. A pilot project investigated the mechanistic-climatic laboratory characterization of materials used to construct test sections on Control Section Highway 15-11 (C.S. 15-11). This research demonstrated the use of ground-penetrating radar and falling weight deflection measurements to select uniform field test section locations. In situ recycled granular base was sampled and found to be a typical thin granular pavement requiring strengthening because it is relatively high in fine sand fraction and has a high portion of intermediate plastic clay fines. These two properties are known to cause marginal performance of granular bases in the field. This research showed that cement and bitu-minous stabilization significantly improved the mechanistic primary response and climatic durability properties of marginal granular base materials. However, it was found that the asphalt emulsion with cement stabilization showed the highest performance improvement. It also was found that the addition of cement to emulsified and foamed asphalt stabilization systems significantly improved the mechanistic-climatic durability of the marginal granular base aggregate. This study demonstrated the rapid triaxial tester to be a pragmatic and cost-efficient methodology to characterize the mechanistic constitutive relations of granular base materials for performing mechanistic road structural modeling.