A mass specific volume-based viscoelastic damage model to characterize fatigue damage in asphalt mixtures

Abstract

Fatigue cracking is one of the most common distresses in flexible pavements, and many damage models have been proposed to predict fatigue cracking, but in these models, the evaluation of damage is related to the choice of the reference configuration, whose subjectivity may lead to subjective evaluation of damage. To describe micro-cracking in asphalt concrete under loading, this paper proposes a new viscoelastic damage model, where damage evolution is connected with the mass specific volume, which is independent of the reference configuration, and the resistance to damage is also represented as an exponential function of mass specific volume to show its decrease under destructive loading. To determine material parameters in the model, nondestructive creep test data are used to obtain the relaxation modulus, and by determining the initial resistance to damage of asphalt concrete with different air voids, the evolution of resistance to damage can be obtained. The rest material parameters can be determined by fitting the destructive test data. To verify the validity of the proposed model, the material behavior under controlled-strain repeated direct tension (RDT) is predicted and the model predictions are compared with test data. It shows and the damage increment in the first loading cycle is largest and the rate of damage increases first and then decreases in each cyclic loading period. In addition, the behavior of the pavement structure under traffic loading is simulated, and fatigue cracking in the asphalt concrete layer of the pavement can be captured by the proposed model. It shows that in thick flexible pavements, both top-down cracking and bottom-up cracking occurs, but top-down cracking is dominant.