Application of the Viscoelastic Continuum Damage Mechanics to Asphalt Mixtures under Indirect Tensile Load

Traditional studies that applied the viscoelastic continuum damage (VECD) model to asphalt materials were mostly accompanied by uniaxial tests whose specimen size requirement provided challenges for mixtures cored from thin asphalt layers. In this paper, an analysis methodology is presented for determining the pseudostrains and damage characteristic curves of asphalt mixtures from both the horizontal (for tension) and vertical (for compression) axes of the indirect tension (IDT) specimen simultaneously. To validate this methodology, laboratory tests were conducted on asphalt specimens in the IDT mode. Complex modulus tests were conducted at various temperatures and frequencies to allow for the construction of a dynamic modulus master curve, which, in turn, was used to obtain the relaxation modulus. In addition, constant-crosshead strength tests were conducted at two temperatures (10 and 20 degrees C) to evaluate the behavior of the asphalt specimens under growing damage. The results of the laboratory study revealed that the damage characteristic curve obtained for compression was located above its counterpart for tension. It also was found that the material showed more favorable damage characteristics at 10 degrees C than at 20 degrees C for both tension and compression and that the damage characteristic curves obeyed the time-temperature superposition principle, which is consistent with the uniaxial test results. These results indicate that the VECD model can be applied to the biaxial IDT test for characterizing tensile and compressive damage characteristic curves simultaneously. (C) 2014 American Society of Civil Engineers.