Modeling of Top-Down Cracking (TDC) propagation in asphalt concrete pavements using fracture mechanics theory

Fatigue is defined as the failure phenomena caused by repeated loading even though the stress due to the loading is less than ultimate strength of the material. Fatigue cracking in asphalt concrete layer is divided into two groups regarding to the place of crack initiation and the type of crack propagation. The first group is the cracks which is initiated in the bottom of asphalt layer and propagates upward. This type of cracking is produced in the asphalt layer with less than 16 mm thickness. The second type of cracking which is produced in thick asphalt layer is initiated in surface area then propagates downward which is called Top-Down Cracking. The second type of cracking is investigated less compared to the first one. One type of analysis and studying fatigue cracking is fracture mechanics approach in which the failure in asphalt mixture is related to number of repeated loading. In this study the fracture mechanics approach was implemented to understand the effective parameters in propagation of top-down cracking. As well as developing a model to interpret the crack propagation in pavement also some graphs were produced for different types of material and loading which gives the length of cracks versus the number of repeated loading.