Method to Quantify Healing in Asphalt Composites by Continuum Damage Approach

The importance of healing and its impact on the fatigue cracking performance of asphalt mixtures are well recognized. Microdamage healing in an asphalt mixture is a function of several factors, such as the physical and chemical properties of the binder, the properties of the mixture, the level of damage before the rest period during which healing occurs, the duration of the rest period, temperature, and pressure. An experimental and analytical method characterizes the healing in an asphalt composite (fine aggregate matrix) as a function of the level of damage before the rest period and the duration of the rest period. The proposed method builds on the viscoelastic continuum damage theory that has been used successfully by other researchers to characterize fatigue cracking in asphalt mixtures. The method is applied to evaluate the healing characteristics of four fine aggregate matrix mixes and is able to quantify the influence of the duration of the rest period and the level of damage preceding the rest period on overall healing. Two verification tests were used to demonstrate that the amount of healing measured by the proposed method was independent of the sequence of loading or rest periods. Results from the initial tests support the hypothesis that the healing characteristics determined with the proposed test method at isothermal conditions can be treated as a characteristic material property.