Ruggedness Evaluation of Dynamic Modulus Test Using Small-Scale Test Specimens for Asphalt Mixture Performance Tester

Abstract

The small specimen dynamic modulus test (AASHTO TP 132-19) is of paramount importance for the asphalt community since it can be used to characterize and compare asphalt mixtures and the test outcomes can be used as input for pavement performance predictions. Even though the small specimen dynamic modulus test is broadly used, acceptable limits for controlling critical experimental factors still need to be developed. This paper presents the method and outcomes of a ruggedness evaluation of the Asphalt Mixture Performance Tester (AMPT) dynamic modulus test using small-scale test specimens. Three mixtures were evaluated and seven experimental factors were selected: strain peak-to-peak magnitude, specimen perpendicularity, platen-to-specimen diameter difference, specimen height, temperature, compensation springs, and end friction reducers. The analysis identified the statistically significant factors and it was found that the strain peak-to-peak magnitude and temperature were the most statistically significant factors. The specimen height and the type of end friction reducer were not found to be statistically significant factors. Also, higher strain levels and the use of compensation springs resulted in the overestimation of modulus at higher temperatures. Finally, tolerance limits were determined for each ruggedness factor and modifications to the small specimen dynamic modulus test and related standards were proposed.