Development of modulus-to-temperature relations for HMA mixtures used in Wisconsin

Abstract

This report presents the findings of a research study conducted to develop modulus-to-temperature relations for Hot Mix Asphalt (HMA) mixtures used in Wisconsin. Surface deflection data gathered from in-place HMA pavements was used to estimate the resilient modulus of the HMA layer at the various test temperatures. Laboratory resilient modulus testing was also conducted on recovered HMA cores to establish trends of HMA resilient modulus as a function of test temperature and load frequency. Prediction equations for estimating modulus-to-temperature trends were developed from laboratory testing to account for mixture-specific parameters, including fines content, air voids and binder content. Estimations of HMA modulus-to-temperature trends based solely on nondestructive deflection data were found to correlate with laboratory trends for some, but not all of the projects tested. Observed estimation errors were deemed due to variations in the thickness and/or stiffness of lower pavement layers which were not measured during field testing. A simple process for developing site-specific variations in HMA resilient modulus in response to monthly air and pavement temperature changes is presented. These monthly variations represent valuable inputs for mechanistic-empirical performance analysis.