Development of a double-torsion fracture test to predict channelized crack behaviors of asphalt concrete

Fracturing of asphalt concrete paving surfaces and overlays is a significant cause of premature pavement deterioration. Fracture mechanics and the proper handling of crack propagation are much needed to understand the mechanisms that are relevant for increasing pavement life. The topic is still quite wide in the field of asphalt pavement design and analysis. This paper shows the experimental development of a double-torsion fracture test for predicting fundamental fracture properties of bituminous materials. Double-torsion test specimens were prepared from a model asphalt material using an automatic French slab compactor. Double-torsion tests were performed at low temperatures to investigate brittle and/or quasi-brittle behavior of bituminous materials. A constant displacement control method was applied to obtain reliable fracture properties of bituminous materials. Test geometry with different notch lengths was considered to obtain a standard specimen configuration without any unexpected failure. Characteristic fracture properties from double-torsion tests were determined based on the linear elastic fracture mechanics theory including compliance. Experimental results showed that the notch length was not a significant factor in the determination of stress intensity factor properties from double-torsion fracture tests on the model material used in this study.