Issue 43

M. Fakhri et alii, Frattura ed Integrità Strutturale, 43 (2018) 113-132; DOI: 10.3221/IGF-ESIS.43.09 128 under various loading rates. Therefore, eight different conditions have been studied relatively and the result is illustrated in Fig. 20 as force-time curves for four loading rates at two temperatures. Higher peak loads can be observed at lower temperatures while more time is needed for a crack to reach the loading point in SCB specimens at higher temperatures. Since the same trend has been reported in this article for fracture energy of AC specimens obtained by load-displacement curves, it can be concluded that the fracture energy calculated and reported in this study can be a proper representative of fracture resistance of asphalt mixtures (with different characteristics) at near zero (5°C) and intermediate temperatures (25°C) under different loading rates. Figure 20 : The effect of loading rates on fracture energy at different temperatures under mixed mode I/II loading condition. C ONCLUSIONS otal number of 229 SCB specimens were tested to study the effect of loading rate on fracture energy of asphalt concrete with different characteristics (aggregate type and air void content) under three loading conditions (mixed mode I/II with M e =0, 0.5 and 1) at intermediate and low temperatures (5 and 25C). Consequently, the following concluding remarks were found:  Under high loading rates of pure mode I loading condition, the fracture resistance of both asphalt mixtures manufactured with lime and silica aggregate are approximately the same, showing the fact that under high loading rates (i.e. highways with high speed limits for passing vehicles), aggregate type does not affect the fracture energy of AC specially at low temperature climates (i.e. 5°C).  Under pure mode I loading condition, the difference between the values of fracture energy at 25°C is less for asphalt mixtures with low percentage of air void (i.e. 3%), since the matrix tends to behave more homogenously and loading rate effects the fracture behavior of AC less, comparing to AC with higher air void contents (i.e. 5 and 7%).  Under pure mode I loading condition, 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 AC in regions with mild climate, shows the most resistance against fracture, comparing to cold and warm climates (with the mean annual temperature value of 5 and 25°C, respectively).  Under low and high loading rates (i.e. 1 and 50 mm/min) of pure mode II loading condition, asphalt mixtures built with lime show more fracture resistance than those manufactured with silica.  Fracture energy reaches its lowest values under low and high loading rates (i.e. 1 and 50 mm/min) for all specimens with different air void contents, while it reaches its highest values under intermediate loading rates (i.e. 5 and 10 mm/min) at 5°C under pure mode II loading condition. T