Characterizing mixed mode I/III fracture toughness of asphalt concrete using asymmetric disc bend (ADB) specimen

• An asymmetric disc specimen was improved to simulate mixed mode I/III loading.
• Mode I/III fracture resistance of asphalt concrete was obtained at low temperatures.
• Fracture resistance decreased as the mode III component added to the mode I.
• By dropping the temperature, fracture resistance initially increased, and then reduced.

Mechanical behavior of asphalt concretes is inherently complicated so for having a safe asphalt pavement, their manner ought to be identified in all aspects. In the present paper, in order to characterize mixed mode I/III fracture toughness of asphalt concrete an asymmetric disc (ADB) specimen containing an inclined crack was employed. This specimen was compressively loaded using a simple three-point fixture. Fracture tests on the asphalt concrete were then performed under mode I, mode III and combined mode I and mode III loading conditions at several sub-zero temperatures (−5 °C, −20 °C, −30 °C). Experimental results demonstrated that fracture resistance of the asphalt concrete decreased at the tested subzero temperatures significantly by adding the mode III component to the mode I at the crack front. Moreover, as the temperature went down, the fracture resistance of the asphalt concrete initially increased until reached its peak value at −20 °C, and then reduced. Meanwhile, the fracture surface was found to be non-planar when the specimens were loaded under mixed mode I/III.