This study presents the results from an analytical and experimental study on the dynamic modulus testing of hot-mix asphalt using the indirect tension (IDT) mode. An analytical solution for the dynamic modulus in the IDT mode was developed with the use of linear viscoelasticity. To verify the analytical solution, temperature and frequency sweep tests were conducted on 12 asphalt mixtures commonly used in North Carolina; both axial compression and IDT test methods were used. A modified dynamic modulus test protocol is introduced to reduce the required testing time by using more frequencies and fewer temperatures on the basis of the time-temperature superposition principle. A comparison of results from the axial compression and IDT test methods shows that the dynamic modulus master curves and shift factors derived from the two methods are in good agreement. It also was found that Poisson's ratio was a weak function of the loading frequency; its effect on the phase angle master curve is discussed.

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This paper presents an Acoustic Emission (AE) characterization of damage accumulation and strength recovery in Asphalt Concrete (AC) mixture. A series of uniaxial tensile cyclic tests with and without rest period has been conducted on a 19 mm nominal maximum size of aggregate (NMSA) AC at 20 o C. During the fatigue tests, key AE parameters including emission counts were acquired from two piezo-type sensors attached to the middle of a 150 mm high, 75 mm diameter cylindrical specimen. Test results indicate that accumulative AE energy and AE count may be used not only to assess the initiation and propagation of fatigue damage, but also to quantify the beneficial effect of rest period on the performance of AC. The frequency-amplitude analysis shows that crack formations coincide with the peaks of maximum AE amplitude (A max ) with higher frequencies, while healing is best described by A max with lower frequencies during the rest periods. In addition, it is demonstrated that the Kaiser effect, the stress dependence of AE generation, does not hold for fatigue in AC.

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