Identification of suitable crack growth law for asphalt mixtures using the Superpave indirect tensile test (IDT)

Mechanisms of crack development and propagation of asphalt mixtures and pavements were studied in this project. As a starting point, fracture tests were performed on eight field sections in order to determine fracture parameters A and n using the system developed in this study. However, discrepancies between the laboratory test results and field performance were observed. Therefore, further investigation was conducted to identify the source of these discrepancies.; It was noted that loading conditions are different between the laboratory and the field. In the laboratory, the specimen was forced to fail under repeated loading conditions, whereas asphalt mixtures may heal under realistic loading condition and/or temperature increases. Based on the preliminary research results, a threshold concept was introduced, which is associated with the key fact that micro-damage is healable if the threshold is not exceeded, while unhealable macro-damage (crack growth) develops once the threshold is exceeded. Evaluation of the threshold concept showed that dissipated creep strain energy may be a suitable threshold for asphalt mixtures.; Finally, an HMA Fracture Mechanics model was developed based on the use of dissipated creep strain energy as a threshold. Preliminary evaluation of the model indicated that this model could rationally predict crack growth on asphalt mixtures. Therefore, further modification and evaluation of this model, including the effect of loading history and healing, were recommended.