Empirical Correlation of Indirect Tension Resilient Modulus and Complex Modulus Test Results for Asphalt Concrete Mixtures

ABSTRACT Dynamic complex modulus is a fundamental property for describing the stress-strain relationship of a viscoelastic material such as the hot mix asphalt (HMA) mixture. The AASHTO Mechanistic-Empirical Design Guide for flexible pavement structures adopted the use of the dynamic complex modulus as the primary test protocol to characterize the modulus response of HMA mixtures. This paper presents a rational comparative study to evaluate the indirect tension resilient modulus and dynamic complex modulus tests for characterizing the Florida asphalt concrete mixtures. The primary objective of the study was to develop a correlation relationship for predicting the dynamic complex modulus from existing resilient modulus values of the asphalt concrete mixtures. An experimental program was developed to evaluate selected Superpave asphalt concrete mixtures with a range of aggregates and mix designs. A total of 18 HMA mixtures were selected and tested for both dynamic complex modulus and resilient modulus. Replicated specimens with the same targeted air void content of 4.0 percent were prepared for each mixture design in order to conduct a comparative study between dynamic complex and resilient modulus test results. Predicted dynamic complex modulus values from the Witczak prediction model were compared with the measured dynamic complex modulus values to verify the dynamic complex modulus test results. The linear regression analysis indicated that the dynamic complex modulus increased with an increase in resilient modulus at a specific loading frequency, and the resilient modulus values were comparable with the dynamic complex modulus values at the loading frequency of 4 Hz. The rational approach outlined in this study could be utilized to establish an empirical correlation for predicting the dynamic complex modulus from measured resilient modulus values of HMA mixtures.