13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 50mm (a) Mesh configuration of the whole beam Observation point (b) Mesh in the mesoscale region (c) Mesh near the crack tip Figure 2. Mesh configuration of the three-point bending beam specimen with a central crack The fracture of asphalt concrete is mainly due to accumulation and coalescence of microscopic cracks existing or induced by load. One of the features of fracture investigation is the proposed criterion for crack growth initiation. By introducing a damage variable in the constitutive relation, the element fractures and a crack occurs when the fracture threshold within the elements is reached in the numerical simulation. Namely the propagation of crack is the migration of damage zone where are equal to the critical damage value gradually for the material of around crack tip. In this paper, the crack is assumed to only grow in asphalt mastic since mastic stiffness weaker than coarse aggregates several quantities and fracture criterion is given based on damage value as follows: c D D= (11) Once the damage value near the crack tip reaches its critical value cD , the fracture occurs and propagates. cD =0.85, which is referred to the results given by Sun et al. [14]. 3. Results and discussion
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