Modifying the Viscosity Based Witczak Model and Developing Phase Angle Predictive Model for New Mexico’s Superpave Mixes

This study modifies the viscosity (η) based Witczak dynamic modulus (|E*|) predictive equation which is used in the recently developed American Association of State Highway and Transportation Officials (AASHTO)Ware pavement Mechanistic-Empirical (ME) design software. A total of 21 Superpave (SP) mixtures with different gradations and binder grades were tested for |E*| at different temperatures and frequencies of loading. Results show that the η-based Witczak model underestimates the |E*| for New Mexico’s SP mixes. Therefore, revised model is developed using regression analysis. A phase angle (ϕ) predictive model is also developed using the ϕ-values obtained during the |E*| testing. It was found that the revised η- based Witczak model determines the |E*| more accurately compared to the original η-based Witczak model.