Modeling Microdamage Healing in Asphalt Pavements Using Continuum Damage Theory

Healing of microcracks has been proved to play an important role in the behavior of asphalt concrete mixtures especially by causing the strength and damage recovery in the material and increasing the fatigue life of pavements. This dissertation presents a method to quantify the amount of healing in asphalt mixtures using Simplified Viscoelastic Continuum Damage (S-VECD) theory and to utilize this model to predict the damage characteristic curve of the material under realistic loading of pavements. The ability of Simplified Viscoelastic Continuum Damage (S-VECD) theory to predict the fatigue behavior of asphalt concrete mixtures under various loading conditions has been demonstrated over the past decade.;Although, pavements are under a pulse-rest type of loading history which happens from axle to axle of passing vehicles, conducting pulse-rest healing tests in laboratory is a very time consuming task due to the inclusion of rest periods. In this study, group-rest tests (interrupted fatigue tests) that are much faster than the pulse-rest tests are utilized to calibrate the healing model. Group-rest tests were conducted at three different temperatures of 10°, 20° and 30°C, and four rest periods of 10, 30, 90 and 270 seconds. The rest periods were applied at different damage levels to investigate the effects of temperature, rest period, and damage state on healing potential of the material. Then it is shown that the effects of temperature and rest period can be combined in a joint parameter named reduced rest period. Using the results of group-rest healing tests and time-temperature superposition principle, a method is proposed to generate healing mastercurves for different damage levels that relates the amount of healing in the material to the test temperature and rest period through the joint parameter, reduced rest period.;The final proposed healing model predicts the damage characteristic curve of pulse-rest healing test from the damage characteristic curve of continuous fatigue test by using the healing function obtained from the group-rest healing tests. Since damage characteristic curve is one of the most important material characteristics to describe the fatigue behavior and plays an important role in the response of the material under loading, the proposed method would be a great step in the prediction of asphalt concrete behavior under realistic loading conditions with rest periods without having to conduct the time consuming pulse-rest healing tests in the lab.