Creep recovery behaviour of bituminous binders - relevance to permanent deformation of asphalt pavements

Abstract

The increase in traffic loads and loading time in road pavements worldwide has resulted in the widespread usage of polymer modified binders (PMBs) since they offer increased resistance to pavement distresses. The extensive use of inherently different modifiers has expanded the range of PMBs to select from when designing pavements in order to avoid pavement deformation. The new binder selection criterion using the Multiple Stress Creep and Recovery (MSCR) protocol as per ASTM D7405 is meant to differentiate the resistance to permanent deformation of different road binders. The MSCR test is essentially a repeated creep-recovery test at a fixed loading/unloading interval. This paper aims to highlight the limitations of the MSCR test but also show how creep tests can differentiate the resistance to permanent deformation for different bituminous binders, whether modified or unmodified. The paper will also illustrate creep as a time-dependent deformation phenomenon that is specific to the rate and magnitude of traffic load.