Abstract
This study develops a new mechanical-based method to determine the complex modulus and modulus gradient of field-aged asphalt mixtures using the direct tension test. Due to the non-uniform aging nature of the field cores, the mechanical responses must be measured at different depths. Meanwhile, the monotonic load is not applied at the neutral axis of the field core specimen due to the modulus gradient, the tensile part of the strain is used and should be separated from the measurement because of the eccentric loading. The modulus gradient parameters, the location of the neutral axis, and the stress distribution are first obtained using the elastic formulas for a series of loading times. Then the complex modulus is determined using the Laplace transform and the elastic–viscoelastic correspondence principle. An inverse approach and iteration are then proposed by using the pseudo strain to accurately calculate the modulus gradient parameters after the relaxation modulus and reference modulus are determined.
Highlights
The dynamic modulus of asphalt mixtures is a material property and one of the most important inputs in the Pavement Mechanistic-Empirical (ME) Design [1]
This study presents a new mechanical method to determine the complex modulus and modulus gradient of field cores using the direct tension test
The strains at different depths of the field core specimens are different, which is related to the modulus gradient, the strains for the LMLC mixtures are almost identical
Summary
The dynamic modulus of asphalt mixtures is a material property and one of the most important inputs in the Pavement Mechanistic-Empirical (ME) Design [1]. Recent studies determine that the thickness for rectangular and cylindrical field core specimens can be as thin as 26 mm (1 inch) for both dynamic modulus test and damage test, and the test results are in the same ranges with those for the standard dimension specimen [8, 9] This valuable conclusion provides a guide for dealing with those with small specimen geometries such as field cores. In these studies, the tested specimens are obtained from different depths of one original field core, which are used to reflect the modulus distribution along the pavement depth.
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