Permanent deformation of asphalt mixture under repeated load can be divided into three phases: decelerating phase, stationary phase, and accelerating flow phase. Most of the existing models cannot fully describe deformation characteristics during the three phases. In this paper, the characteristics of three-phase permanent deformation are considered as the results of a competition between damage and hardening, in which a damage variable and a hardening variable are introduced to modify Burger’s model. First, the series-wound dashpot of the Burger’s model is modified by Usan’s hardening variable, and the undamaged viscoelastic properties are derived from rheological theory. Secondly, Kachanov’s equation for damage evolution is adopted to establish the constitutive model by using Lemaitre’s effective stress principle. Then a repeated load consisting of a haversine loading period and rest period is employed to simulate the actual vehicle loading on the asphalt pavement. Third, a viscoelastic-damage m...

In order to effectively repair cracks in the asphalt upon exposure to light, the paper studies the influence of distinctive chemically synthesized conditions of oxetane-substituted chitosan polyurethane (OXE-CHI-PUR) network self-healing agent for self-healing effect of asphalt at different pH values, doses of OXE and doses of catalyst to determine the optimal synthesis conditions. The study suggests that the optimall synthetic conditions for the self-healing agent include optimal pH = 6.8 , the optimum dose of OXE:CHI = 1:5 and the optimum dose of catalyst (dibutyl tin dilaurate) = 2%.

This paper is studies how temperature and stress affect creep characteristics of asphalt mixture synthetically based the time-temperature-stress equivalence principle of asphalt mixture. Firstly, static uniaxial creep tests of an AC20 asphalt mixture are conducted at 40, 50 and 60 °C while the axis stresses are 0.2MPa, 0.4MPa and 0.6MPa to study the effects of temperature and stress on creep characteristics. Then the time-temperature-stress equivalence principle is applied to analyze the time-temperature-stress shift factor. It is indicated that the influence of stress on creep characteristics is similar to the influence of temperature for the asphalt mixture, and stress exert the same influence on the viscosity as temperature. The united time-temperature-stress shift factor given by three methods are approximately equal.

The indirect tensile test was used to study the influences of asphalt binder properties, aggregate surface properties and loading conditions on asphalt mixture performance. Marshall digital specimens were generated by discrete element method (DEM) and the servo-control mechanism was used to apply the loading. The influence laws of the bond strength ratios, the bond stiffness ratios, the particle friction coefficients and the loading velocities on the stress-strain curves, the splitting strengths, the coordination numbers and the micro-cracks were analyzed. The results show that the variation of the splitting strengths, the coordination numbers, and the micro-cracks caused by the bond strength ratios are the greatest, the coefficients of variation of the splitting strengths and the coordination numbers are 56.9% and 5.9%, respectively, and the difference between the most number of micro-cracks and the fewest number of micro-cracks is 43. However, the variation of the splitting strengths, the coordination numbers, and the micro-cracks caused by the loading velocities are the smallest, the coefficients of variation of splitting strengths and coordination numbers are 2.3% and 1.7%, respectively, and the difference of the number of micro-cracks is only 1. The results verify that the contribution of asphalt binder properties to the crack resistance of asphalt mixture is dominant from the mesoscopic viewpoint.