Prediction of the complex modulus of asphalt mixture containing RAP materials from the rheological properties of mortars

In this paper, the properties of mortars that proportionally contain the same amount of fresh and RAP binder which can be found in the asphalt mixture, with respect to the specific material phase, are modeled with the objective of predicting the rheological behavior of the corresponding recycled mixture. For this purpose, Dynamic Shear Rheometer (DSR) tests are performed to determine the complex moduli of asphalt binders and mortars, which are then used as input in the empirical Hirsch and Witczak models. Based on the better predictions obtained from the latter, a modified formulation of the Witczak model was successfully derived to predict the mixture complex modulus directly from the experimental data of the corresponding asphalt mortar. The predictions obtained with the newly proposed expression of the Witczak model, closely match the laboratory measured complex modulus of asphalt mixtures. This can be used as input in the Mechanistic-Empirical Pavement Design Guide to analyze stress, strain, and deflection of asphalt pavements.