Volume 40, Issue 6 (November 2012)
Comparison of Dynamic Moduli for Asphalt Mixtures Determined from Different Geometries and Compactions
The MEPDG (ARA, Inc., “NCHRP 1–37A Final Report: Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures,” NCHRP Program 1–37A Project, National Research Council, Washington, D.C., 2004) introduces the dynamic modulus as the material property to characterize asphalt concrete. One of the challenges of acquiring the dynamic modulus from existing pavements is the standard dimensions of the test specimen. The specimen size specified in AASHTO TP62–07 (2007, “Standard Method of Test for Determining Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures,” AASHTO, Washington, D.C.) cannot be obtained from many pavement layers. This study evaluates two other geometries, indirect tension specimens and prismatic specimens, to determine whether the measured dynamic modulus is the same as the modulus obtained from TP62 protocol. This study provides a comparison of the effects of a non-uniform state of stress and anisotropy. These effects are isolated by comparing specimens prepared by Superpave gyratory compaction and vibratory steel-wheel compaction. The comparisons are verified using four 12.5-mm surface course mixtures with different aggregate shapes and binder types, and one 25.0-mm base mixture. The results show that the difference between the dynamic modulus values obtained from different geometries is statistically insignificant. The results provide justification for using alternative methods for acquiring the dynamic modulus experimentally—specifically, for previously constructed pavements.