Investigating the Use of a Binder Cohesion Test to Evaluate Cracking Resistance of Asphalt Mixtures

A number of different factors influence the overall performance of asphalt binder and consequently asphalt mixtures. These include intrinsic factors such as the use of modifiers, additives, reclaimed asphalt pavement (RAP) and other extenders. In particular, the fracture resistance of the asphalt binder is of importance because of the role of asphalt binder in resisting the tensile stresses in an asphalt mixture. Existing tests and metrics commonly used to quantify the cracking resistance of the asphalt binder suffer from some drawbacks. Specifically, most commonly used tests are based on rheological measures that do not induce damage in the test specimen and/or tests that subject the asphalt binder to a stress state that is not representative of the stress state that the binder experiences in an asphalt mixture. It was hypothesized that the poker-chip test geometry and parameters obtained from conducting a tensile strength test using this geometry could be used as an indicator for the cracking resistance of asphalt binders. A test protocol was developed in order to validate the efficacy of this method. Crack resistance tests were performed using two different mixture performance tests, the overlay test (OT) and the indirect tensile strength (IDT) test, on 16 different asphalt mixtures. The binders extracted and recovered from these mixtures were evaluated using the poker-chip test method. This study demonstrates that a tensile strength test conducted using the poker-chip geometry can be used as an indicator of cracking resistance of asphalt binders.