Interconversion of Dynamic Modulus and Resilient Modulus of Asphalt Mixtures to Evaluate the Short-Term Laboratory Conditioning

The National Cooperative Highway Research Program (NCHRP) 1-37A mechanistic-empirical pavement design guide (MEPDG) ushered in a transition from resilient modulus to dynamic modulus as the material property representing the stiffness characteristic of layer materials. This transition may make a significant amount of the resilient modulus databases that have been collected by state highway agencies over many years obsolete unless a method for the conversion of these stored values to dynamic modulus values is developed. This study uses an existing predictive model to predict the dynamic modulus from the resilient modulus and vice versa. This model was originally developed to populate the long term pavement performance (LTPP) database with dynamic modulus values. The purpose of this study is to evaluate the short-term laboratory conditioning of asphalt mixtures for mix design and performance testing to simulate the effect of plant mixing and field performance by assessing the evolution of mixture stiffness. Therefore, a comprehensive database including asphalt concrete mixtures with a full range of hot mix asphalt (HMA) and warm mix asphalt (WMA) production temperatures has been assembled and processed. The collected database now includes sets of dynamic modulus and resilient modulus values which were predicted from one another by applying the existing artificial neural network (ANN) models that includes both forward and backward approach. Also, analysis of variance (ANOVA) was used in order to correlate the predicted results with an available set of laboratory measured dynamic modulus values and to study the mixture behaviour of various plant and laboratory mixtures involved.