13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- σ ε 0 cσ fε uε D ε 0 1 fε uε (a)curve of stress-strain (b)curve of damage evolution Fig. 2 curves of the proposed damage model 2.2. Aggregate generation and packing algorithm Utilizing a self-compiled algorithm, all spheric aggregates (or round aggregates for 2D) are converted into their corresponding inscribed polyhedra (or regular polygons). The detail of the algorithm was described in the work of Yin et al. [11, 12]. For convenience, the somplete aggregate gradation listed in Table 1 was treated as a simplified aggregate gradation listed Table 2. Two 2D mesostructural asphalt concrete specimens of different coarse aggregate distributions with the gradation simplified aggregate are created by the generation and packing algorithm, shown in Fig.1 (a) and (b), respectively. In those two figures, the black region represents asphalt mastic and the white regular octagons are graded coarse aggregates. Table 1. Complete aggregate gradation Sieve size (mm) 16.0 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Passing rate (%) 100 98.1 80.8 52.2 34.1 27.5 20.6 14.1 9.9 7.7 Table 2. Simplified aggregate gradation Sieve size (mm) 16.0 13.2 9.5 4.75 2.36 Passing rate (%) 100 98.1 80.8 52.2 34.1 （a）
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