Permanent Deformation of Various Unbound Aggregates Submitted to Seasonal Frost Conditions

Pavement performance in northern climate as encountered in Canada is significantly influenced by frost action. When it comes to granular materials used in flexible pavement foundations, few study focused on the effect of seasonal frost conditions on the mechanical properties of such materials, mostly because such materials are usually considered as non-sensitive to such environmental solicitation. As it is well known that seasonal frost conditions may cause an increase of water content as well as a loosening of granular assemblies, the effect of frost action on the long term performance, expressed as resistance to permanent deformation, of base granular materials was measured for various aggregate sources and two gradings through a comprehensive laboratory study based on cyclic triaxial testing. Five saturated samples were used as reference and 5 samples were tested following a freeze-thaw cycle. It was found that the freeze-thaw cycle has a more important effect than grading and that it mainly influences the samples post-compaction magnitude. Moreover, following a freeze-thaw cycle, the percentage of the final permanent deformation that is related to post-compaction usually increases, as the post-compaction model parameter was found to increase and as the permanent deformation rate model parameter was found to slightly decrease.