Effect of Test Methods on Viscosity Temperature Susceptibility Characterization of Asphalt Binders for the Mechanistic-Empirical Pavement Design Guide

The Superpave asphalt binder specifications are intended to improve pavement performance by limiting the potentials for plastic deformation and cracking. Hot-mix asphalt (HMA) behavior depends on the binder's—temperature susceptibility, and the rate of loading. The binder viscosity temperature susceptibility (VTS) characterization plays a major role in determining the HMA dynamic modulus (E*) master curve, especially when input Level 3 is used in the M-E PDG. For input Levels 2 and 3, E* could be predicted by the Witczak equation, whereas, three test methods are specified to determine the asphalt binder VTS. These tests are (i) dynamic shear rheometer (DSR) for determining shear modulus (E_b*) and phase angle (δ); (ii) conventional tests such as penetration, kinematic and absolute viscosities, and ring and ball softening point; and (iii) rotational viscosity. All test methods can be utilized to determine the ASTM "A-VTS" parameters. In this paper, the A-VTS parameters for twenty two (22) neat and polymer modified binders were obtained from the three test methods and compared. The results show that A-VTS parameters from the three tests could be significantly different. Further, the impact of the VTS parameters' variations on the E* master curve and on the predicted flexible pavement performance are discussed.