Use of Mechanistic-Empirical Pavement Design Guide for Mix Performance Evaluation Using the Dynamic Modulus Application to Mix Rutting

The Virginia Department of Transportation has worked toward end-result specifications (ERS) in hot-mix asphalt (HMA) since the mid-1960s. With the recent advances in HMA material characterization and the completion of the new Mechanistic Empirical Pavement Design Guide (MEPDG) under NCHRP Project 1-37, the ultimate goal of true ERS that are performance related seems more feasible. The use of the HMA dynamic modulus as an HMA quality measure is investigated. An effective reduced frequency (temperature frequency combination) at which the HMA dynamic modulus best correlates with the MEPDG-calculated HMA rutting is determined for eight climatic conditions. This effective reduced frequency did not coincide with the modified Witczak effective temperature frequency equation. The effect of HMA layer thickness (51 to 254 mm) on effective reduced frequency was investigated for Roanoke, Virginia. It was found that layer thickness had a minor effect on effective reduced frequency, so that the latter can be assumed independent of layer thickness for all practical purposes. Finally, the HMA rutting calculated by using the effective reduced frequency was found comparable with the MEPDG-calculated HMA rutting with average and maximum differences of 6.5% and 23%, respectively. This difference is acceptable considering the variability in actual field rutting measurements (for the same conditions) as well as accuracy of the MEPDG in determining the average HMA field rutting. Use of the effective reduced frequency can result in considerable time and money savings, especially for quality assurance applications for which testing is regularly performed.