Dynamic Complex Modulus of Mn/ROAD Asphalt Mixtures

This paper presents the results of laboratory testing to determine the complex dynamic modulus and phase angle of asphalt mixtures. Laboratory tests were performed on four different asphalt mixtures containing PG 58-28, PG 58-34, PG 58-40, and 120/150 penetration (PG 58-28) asphalt binders from the Minnesota Road Research Project (Mn/ROAD). Data from the tests were processed through a nonlinear regression curve fit to generate master curves of dynamic modulus and phase angle versus frequency. These master curves were compared to results obtained from Witczak’s predictive equations. It was found, as expected, that the dynamic modulus increased with an increase in frequency and a decrease in temperature. The model used to fit dynamic modulus master curves provided a good fit for the experimental data. The modulus values calculated using the 2000 predictive equation fit the test data reasonably well for Cell 21 and 35 mixtures, but the differences for Cells 33 and 34 were more significant. Smooth master curves for phase angle could not be obtained. This study was done under the framework of National Cooperative Highway Research Program (NCHRP) Projects 1-37A, 9-19, and 9-29 that recommend dynamic modulus as both a design parameter and a simple performance test.