Novel Procedure for Accurately Characterizing Nonlinear Viscoelastic and Irrecoverable Behaviors of Asphalt Binders

The multiple stress creep recovery (MSCR) test has been extensively recognized as a more effective method for characterizing the rutting resistance of asphalt binders than the traditional linear viscoelastic (LVE) theory–based Superpave performance grading (PG) test that determines the rutting parameter. However, recent studies have shown that the MSCR test has a major limitation in that the 9-s recovery period in each cycle may not allow complete recovery of the delayed elasticity, particularly for modified binders, which implies that the definitions of the parameters from the MSCR test, e.g., the nonrecoverable compliance $J_{\mathrm{nr}}$, are not the strictest ones. To accurately separate and obtain the actual irrecoverable and recoverable responses of binders from the MSCR test, this study developed a new procedure that uses the full Schapery nonlinear viscoelastic (NLVE) model and the LVE properties from the frequency sweep test. The results showed that the presented approach overcomes the deficiencies of existing methods, and can accurately and effectively characterize the NLVE and irrecoverable behaviors of the binders, regardless of whether they were polymer-modified or neat, and can guarantee the consistency of the material information from the traditional PG test and the MSCR test. Because of these advantages, the procedure provides a potential approach for further analyzing and modeling the rutting behavior of the corresponding asphalt concrete.