Issue 47

M. Fallah Tafti et alii, Frattura ed Integrità Strutturale, 47 (2019) 169-185; DOI: 10.3221/IGF-ESIS.47.14 178 The fracture energy is equal to the area under the load-displacement curve divided by the effective area of the fracture. It implies that a specimen with higher fracture energy capacity would absorb higher energy before reaching to the fracture point. It can be calculated using Eqn. (2) below. f f lig W G A  (2) where f G , f lig W and A are fracture energy, work to breakdown a specimen or the area under the load- displacement curve and ligament area, respectively. Fracture Energy of Specimens Fracture Toughness of Specimens Modified/Unmodified HMA Specimen Type % Change modified versus control COV (%) Average (J/m 2 ) %Change modified versus control COV (%) Average (MPa.m 0.5 ) - 13.1 931 - 4.9 0.965 Unmodified (control) 31.79 8.7 1228 22.28 15.1 1.187 PACSF 0.05 44.95 15.1 1350 35.55 11.5 1.308 PACSF 0.075 53.48 4.3 1430 40.4 6.8 1.356 PACSF 0.1 4.07 5.3 969 1 16.2 0.974 Sulfur Polymer 30 8.15 2.4 1007 11.74 6.6 1.087 Sulfur Polymer 40 13.87 3.7 1061 24.14 8.4 1.152 Sulfur Polymer 50 11.22 6.4 1036 -1 13 0.957 EPS 5 14.15 2.5 1063 -3.3 8.4 0.935 EPS 10 20.73 3.1 1125 6.63 8.8 1.029 EPS 15 30.09 2.5 1212 13.98 8.1 1.140 Parafiber 0.1 39.88 5.1 1303 25.38 9.7 1.254 Parafiber 0.15 48.93 3.4 1387 36.78 10.3 1.344 Parafiber 0.2 18.13 7.5 1100 12.33 6.2 1.084 Sasobit 2 26.14 7 1175 19.84 8.9 1.156 Sasobit 2.5 37.37 2.6 1279 30.21 7.6 1.256 Sasobit 3 Table 7 : Average, COV and % change values of the fracture toughness and fracture energy for each specimen type. A NALYSIS OF RESULTS AND DISCUSSION ollowing the experiments, the average and covariance (COV) values of the measured fracture toughness and fracture energy for specimens with similar modifier type and proportion were calculated. Also, the percentage increase in the average fracture toughness of each specimen type in comparison with the control specimen (the similar specimen F