Issue 43

M. Fakhri et alii, Frattura ed Integrità Strutturale, 43 (2018) 113-132; DOI: 10.3221/IGF-ESIS.43.09 121 Figure 7 : Effect of Air void content on fracture energy at 5°C under pure mode I loading condition. Figure 8 : Effect of Air void content on fracture energy at 25°C under pure mode I loading condition The effect of testing temperature on fracture energy under pure mode I loading condition To investigate the effect of loading rate at a wider range of temperatures, Fig. 9 shows the variations of AC fracture energy with different test temperatures to study the change in asphalt mix fracture behavior from quasi-brittle at near zero temperature to viscoelastic at intermediate temperature. By increasing loading rates at 5°C, fracture energy change trend is peaky (increasing to reach a maximum value and then decreasing) while at 25°C it is increasing by a constant slope. Although testing temperature of 15°C seems to be a transition temperature for AC fracture behavior. As it is obvious from test results shown in Fig. 9, the most resistance against fracture can be expected from AC under loading rate of 5 mm/min at low temperature conditions (i.e. 5°C). Moreover, at higher temperatures (i.e. 25°C), increasing loading rate increases fracture energy with a more gentle slope comparing to other two temperatures (5 and 15°C). At transition temperature (15°C), mean value of fracture energy for four loading rates, is higher comparing with two other temperatures (5 and 15°C), showing that