CORRELATION OF SUPERPAVE G*/SIN DELTA WITH RUTTING SUSCEPTIBILITY FROM LABORATORY MIXTURE TESTS (WITH DISCUSSION AND CLOSURE)

The objective of this study was to compare the Superpave G*/sin delta of five binders with the rutting parameters given by laboratory mixture tests. Superpave uses the G*/sin delta from the dynamic shear rheometer to specify binders according to rutting susceptibility. The conventional designations for the five binders are AC-5, AC-10, AC-20, Novophalt, and Styrelf 1-D. All five binders were used in a surface mixture having a nominal maximum aggregate size of 19.0 mm. The AC-5 and AC-20 binders were also used in a base mixture having a nominal maximum aggregate size of 37.5 mm to determine whether the effects of binder type on rutting susceptibilty varies with maximum aggregate size. The data showed that binders with higher G*/sin delta produce mixtures less susceptible to rutting. The Georgia loaded-wheel tester provided a very good relationship between G*/sin delta and rutting susceptibility. The French pavement rutting tester and Hamburg wheel-tracking device provided reasonably good relationships. The main discrepancy for these latter two devices was that even though the Styrelf mixture had a very low susceptibility to rutting, the data suggest that the rut depths are slightly high compared with the G*/sin delta of the binder. The data also showed that increased maximum aggregate size did not significantly reduce the effects of binder type on rutting susceptibility. The Marshall stabilities and flows and the gyratory testing machine data did not differentiate between the mixtures according to rutting susceptibility; therefore, there were no relationships between these tests and G*/sin delta.