Evaluation of Multiple Stress-Creep Recovery Test on Alaskan Asphalt Binders

Abstract

Although the multiple stress creep recovery (MSCR) test has shown its superiority in predicting rutting resistance of asphalt binders, concerns have been raised regarding the testing protocol and procedures. To evaluate the rutting resistance and investigate the suitability of the standard MSCR test method for Alaskan binders, nine typical Alaskan asphalt binders from three different suppliers were collected from paving projects and tested using MSCR tests with four different testing protocols and procedures. The results indicated that the modified binders had better rutting resistance than the neat binder regardless of performance grade (PG). The nonlinear stress limits of most modified binders were all found to be less than 3.2 kPa, which indicated that the stress level of 3.2 kPa included in current specifications could identify their nonlinear behavior. A higher stress level was recommended for identifying the nonlinearity of Binder 3 (PG 64-40 from Supplier A). The recovery time and the number of load cycles had significant effects on the nonrecoverable creep compliance (Jnr) and percent recovery (R) values of polymer-modified binders. Based on the testing results, it was recommended that at least 30 load cycles be included at each stress level and that the strain data from the last five cycles be used to calculate the Jnr and R values. The Jnr-diff included in current one current standard was found unwarranted to evaluate the stress sensitivity of the Alaskan polymer-modified binders used in this study.