Predicted E* dynamic moduli of the Arizona mixes using asphalt binders placed over a 25-year period

Abstract

The objective of this study was to predict the E* dynamic moduli of the actual field mixtures placed in Arizona using more than 25years of data at two different levels of aging: original and RTFO aged conditions. E* predictions were based upon the three global E* predictive equations: Hirsch, NCHRP 1-37A, and NCHRP 1-40D Models. A total of 2834 test sections were used for E* predictions at ten temperatures amounting to a total of 28,340 data points for each aging condition. In general, E* decreased with increasing temperature for all the three models at two aging conditions with the predicted E* for RTFO mixtures being higher than the original by at least 40%. At both aging conditions, NCHRP Models had excellent correlations (R2>0.90) with respect to the Hirsch Model with low bias and high precision. Sensitivity of the model parameters was evaluated using aggregate size, air voids, and asphalt content at three temperatures for both aging conditions. Prediction performance was assessed by comparing the predicted and measured E* on similar mixtures; best predictions were obtained by NCHRP 1-40D Model, followed by Hirsch and NCHRP 1-37A Models. It is envisioned that these E* prediction assessments are deemed to be helpful in examining the field asphalt mixtures’ aging and pavement performance, based on the MEPDG where actual E* tests are not possible/practicable to be conducted.