Evaluation of the low temperature fracture resistance of asphalt mixtures using the semi circular bend test

The use of a Semi Circular Bend test as a candidate for a low-temperature cracking specification was studied. Three similar Superpave mixtures with different asphalt binders (PG 58-40, PG 58-34, and PG 58-28) used in the MnRoad pavement facility were tested at -30°C and -40°C and fracture properties were obtained. For the stiffness calculated as the slope of the load-displacement curve neither the binder type nor the specimen location were significant. For the fracture toughness and in particular for the fracture energy, the binder type effect was significant. At -30°C, the fracture energy ranked the mixture in the same order as their binder PG: the highest was determined for the PG 58-40 and the lowest for the PG 58-28. However, the fracture toughness indicated that the PG 58-34 mixture was about the same as the PG 58-40 mixture. At -40°C, both parameters ranked the mixture in the same order as their binder PG. The toughness evolution with temperatures showed that as the temperature dropped from -30° to -40°C, the toughness for mixture 58-40 increased while for mixtures 58-28 and 58-34 decreased. The fracture energy evolution with temperatures showed that the fracture energy drops as the temperature decreases. The trend observed in both the fracture toughness and fracture energy data suggested that below the binder PG lower limiting temperature very little change in fracture resistance occurs which is in agreement with the asymptotic behavior observed in the rheological characterization of asphalt binders. This is an abstract of a paper presented at the Association of Asphalt Paving Technologists 2004 Technology Sessions (Baton Rouge, LA 3/10-18/2004).