ASTM D7313-07a

The test method was developed for determining the fracture resistance of asphalt-aggregate mixtures. The fracture resistance can help differentiate mixtures whose service life might be compromised by cracking. The test method is generally valid for specimens that are tested at temperatures of 10°C (50°F) or below (see Note 1). The specimen geometry is readily adapted to 150-mm diameter specimens, such as fabricated from Superpave (trademark) gyratory compactors (Test Method D 6925), that are used for the asphalt concrete design process. The specimen geometry can also be adapted for forensic investigations using field cores of pavements where thin lifts are present. This geometry has been found to produce satisfactory results for asphalt mixtures with nominal maximum aggregates size ranging from 4.75 to 19 mm.

Note 1—The stiffness of the asphalt binder tends to influence the assessment of a valid test as described in 7.4. For instance a soft asphalt binder, which may be required for a very cold climate might not lead to a mixture that would produce valid results at 10°C and conversely, a hard asphalt binder utilized in hot climates may require higher temperatures to provide any meaningful information.

Note 2—The quality of the results produced by this test method are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D 3666 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this test method are cautioned that compliance with Specification D 3666 alone does not completely assure reliable results. Reliable results may depend on many factors; following the suggestions of Specification D 3666 or some similar acceptable guidelines provides a means of evaluating and controlling some of those factors.

1.1 This test method covers the determination of fracture energy (G_f) of asphalt-aggregate mixtures using the disk-shaped compact tension geometry. The disk-shaped compact tension geometry is a circular specimen with a single edge notch loaded in tension. The fracture energy can be utilized as a parameter to describe the fracture resistance of asphalt concrete. The fracture energy parameter is particularly useful in the evaluation of mixtures with ductile binders, such as polymer-modified asphalt concrete, and has been shown to discriminate between these materials more broadly than the indirect tensile strength parameter (AASHTO T322, Wagoner ). The test is generally valid at temperatures of 10°C (50°F) and below, or for material and temperature combinations which produce valid material fracture, as outlined in 7.4.

1.2 The specimen geometry and terminology (disk-shaped compact tension, DC(T)) is modeled after Test Method E 399 for Plane-Strain Fracture Toughness of Metallic Materials, Appendix A6, with modifications to allow fracture testing of asphalt concrete.

1.3 The test method describes the testing apparatus, instrumentation, specimen fabrication, and analysis procedures required to determine fracture energy of asphalt concrete and similar quasi-brittle materials.

1.4 The standard unit of measurement for fracture energy is Joules/meter² (J/m²) [inch-pound/inch² (in.-lbf/in.²)].

1.5 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the test method.

1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.