Creep-recovery behavior of bituminous binders and its relation to asphalt mixture rutting

Rutting is one of the main distress modes of asphalt pavements, especially after prolonged warm periods, and thus a great deal of research has been focused on the development of a rheological parameter that would address the rutting susceptibility of both unmodified and modified bituminous binders. In this study the Multiple Stress Creep Recovery (MSCR) test method is used to investigate the creep-recovery behavior of various bituminous binders and its relation to asphalt mixture rutting. Frequency sweep and MSCR tests were conducted on three unmodified and six elastomer and/or wax modified binders, and the resulting data were used to calculate the values of various binder rutting parameters. These binders were also used to manufacture asphalt slabs for mixture rutting simulations in the LPC wheel tracking device. It was found that the non-recoverable creep compliance parameter (J_nr3200) and the accumulated strain at the end of the MSCR test (γ_acc) correlate very strongly with each other and that they both have a superior capability of predicting asphalt mixture rutting compared to other rheological binder rutting indicators. An effort was made to explain the manifested nonlinear viscoelastic properties of the modified binders with their expected microstructural characteristics. The use of the MSCR test in the rutting characterization of bituminous binders is highly recommended based on the results of this research.