5.1 The stiffness and m-value describe the low-temperature stress-strain-time response of asphalt binders. The stiffness and m-value are fundamental material properties and may be used to characterize the linear viscoelastic behavior of asphalt binders at low temperatures.

5.2 The low-temperature thermal cracking performance of asphalt pavements is related to the stiffness and m-value of the asphalt binder contained in the mix.

5.3 The stiffness and m-value are used as performance-based specification criteria for asphalt binders in accordance with Specifications D6373 and D8239.

5.4 The bending beam rheometer is used to determine ΔT_C as defined in Practice D7643.

Note 1: The quality of the results produced by this standard 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 D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.

1.1 This test method2 covers the determination of the creep stiffness or compliance and m-value of asphalt binders by means of a bending beam rheometer. It is applicable to material having stiffness values in the range of 20 MPa to 1 GPa and can be used with unaged material or with materials conditioned with procedures such as Test Method D2872 or Practice D6521. The test apparatus is designed for testing within the temperature range from –36 °C to 0 °C.

1.2 Test results are not valid for test specimens that deflect more than 4 mm or less than 0.08 mm when tested in accordance with this test method.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 Warning—Mercury has been designated by the United States Environmental Protection Agency (EPA) and many state agencies as a hazardous material that can cause central nervous system, kidney, and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for details and EPA’s website—http:// www.epa.gov/mercury/faq.htm—for additional information. Users should be aware that selling mercury, mercury-containing products, or both, into your state may be prohibited by state law.

1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.