Complex Modulus Determination of Asphalt Concrete Using Indirect Tension Test

Abstract

The purpose of this research is to present the results from an analytical/experimental study on the dynamic modulus testing of hot mix asphalt (HMA) using the indirect tension (IDT) mode. The analytical solution for dynamic modulus determination in IDT was developed by Kim (14) using the theory of linear viscoelasticity. To verify the analytical solution, temperature and frequency sweep tests were conducted on 24 asphalt mixtures commonly used in North Carolina, using both axial compression and IDT test methods. In doing so, a modified dynamic modulus test protocol is introduced that reduces the required testing time by using more frequencies and fewer temperatures based on the time-temperature superposition principle. A comparison of results from the axial compression and IDT test methods shows that the dynamic modulus mastercurves and shift factors derived from the two methods are in good agreement. It was also found that Poisson's ratio is a weak function of the loading frequency; its effect on the phase angle mastercurve is discussed. After verification of the analytical solution, another study was conducted to evaluate the effect of aggregate size on the variability of test results, where the coefficient of variation (CV) was computed for each aggregate size and the results were compared. It was found that mixes with a larger nominal maximum size of aggregate (NMSA) had a greater CV than those with a smaller NMSA. Digital image Correlation was used to further support the findings and reveal physical explanations for the results obtained from this statistical analysis.