Strain Measurements in Asphalt Concrete Specimens towards the Development of a Fracture Model

The phenomenology of asphalt concrete (AC) fracture is studied in the laboratory under uniaxial-tension controlled-strain conditions. A specially devised method for measuring local surface strains is described and used to visualize the load-induced damage evolution. It is shown that in pre-peak stress conditions, induced damage is a result of formation, growth, and coalescence of micro-cracks, and that the process is, in essence, three dimensional and random - related to the aggregate packing within the mix. During post-peak stress conditions, it is shown that a process of damage localization occurs within the representative volume element (RVE) leading to the creation of a dominant failure surface (and eventually fracture). The cohesive crack model (CCM) is proposed as an adequate mechanistic fracture model that can account for the above described failure process. A limited testing program was conducted as an initial step towards characterizing the material according to the model. Preliminary results and findings are presented and discussed.