Comparing resilient modulus and dynamic modulus of hot-mix asphalt as material properties for flexible pavement design

With the current trend toward developing mechanistic flexible pavement design and the need for more reliable deafen procedures, accurate characterization at hot-mix asphalt (HMA) properties is needed. Resilient and dynamic modulus tests were performed at five temperatures on two typical mixes used in the Commonwealth of Virginia to compare the test result. The dynamic modulus was measured at six frequencies at each of the testing temperatures, and the resilient modulus test was performed at one loading time. The study found that the size of the specimen statistically affected the measured resilient modulus value. Resilient modulus values obtained in the 100-mm-diameter specimens were higher than those obtained in the 150-mm-diameter specimens at all testing temperatures. No statistical differences were observed in the resilient modulus of the two mixes. However, statistical differences were found in the dynamic modulus of the two mixes. A strong relation between the dynamic modulus test performed at 5 Hz and the resilient modulus was found. Three different pavement structures were analyzed to estimate the variation of their bottom-up fatigue life when different moduli were used for the HMA layer. It was found that the measured dynamic moduli resulted in the highest fatigue life estimates for the three considered pavements. It is concluded that the dynamic modulus test provides a better characterization of HMA than the resilient modulus test because it provides full characterization of the mix over temperature and loading frequencies.