Within the working program of CEN TC336 WG1 (Bituminous Binders) a round robin test has been performed on the fracture toughness test for bituminous binders (CEN/TS15963). The fracture toughness test is a three-point bend test on a pre-notched bituminous beam and aims to determine a temperature at which the binder becomes brittle. Such temperature relates to crack propagation (the formation of a fatal crack) and should demonstrate improved sensitivity at low temperatures for bituminous materials than the currently available tests. The fracture toughness test originates in the field of materials engineering where it is used for determining the toughness of plastic and metallic materials. Eight laboratories participated in the round robin test, in which four different binders have been evaluated: two paving grade binders and two polymer modified binders. The round robin test has shown that the fracture toughness can be a more discriminative test than Fraass breakpoint or the Bending Beam Rheometer to evaluate the low temperature performance of fundamentally different binders. Consistent sample preparation and treatment are key parameters in achieving repeatable and reproducible results. The results have shown that experience with the test and diligent specimen preparation make it a test that is worthwhile to consider for characterising the low temperature behaviour of binders.
