Development of a single-edge notched beam test for the study of asphalt concrete fracture

The fundamental mechanisms behind the initiation and propagation of reflective cracks in asphalt concrete overlays are not well understood. A novel approach is currently underway to investigate reflective cracking by integrating laboratory tests and numerical analysis to develop and validate an approach to predict reflective cracking in pavement structures. Asphalt overlays are subjected to thermal and mechanical loadings, which induce a combination of tension and shear in the overlay. The selection of a laboratory fracture test that has the ability to induce a range of mode-mixity at the crack tip is paramount for the integrated approach to be successful. A promising test geometry that has successfully been used for obtaining Mode I (tensile opening) fracture properties of asphalt concrete is the single-edge notched beam (SE(B)). With a slight modification to the notch location, mixed-mode (combination of opening and shearing) fracture can be investigated with the notched beam geometry using the same testing fixtures, instrumentation, etc. Test procedures have been developed for the SE(B) test that allow investigation of the crack front profile, discrete crack growth using crack detection gages, and variation of fracture energy with temperature. A single mixture was tested using the proposed mixed-mode test geometry with various notch offsets. Through the initial stages of the SE(B) test development, the test provided satisfactory results in terms of the expected trends in fracture energy.