Significance and Use
5.1 The thermal strain measurements allow for the calculation of the coefficient of axial thermal contraction, which can be directly used in the mechanistic-empirical pavement design methods.
5.2 The thermal stress and strain measurements allow calculations of the modulus of asphalt mixture in the temperature domain.
5.3 From modulus versus temperature and thermal stress versus temperature relationships the thermal viscoelastic and fracture properties are determined for asphalt mixtures.
5.4 The derived modulus, thermal viscoelastic, and fracture properties may be used in evaluating the low-temperature cracking resistance of asphalt mixtures.
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.
Scope
1.1 This method of test is used to determine the thermal viscoelastic and thermal volumetric properties of field-cored or laboratory-compacted asphalt mixture specimens by measuring the thermally induced stress and strain while being cooled at a constant rate from an initial equilibrium temperature. The thermal stress and strain shall be measured using the uniaxial thermal stress and strain tester (UTSST).
1.2 This standard test method covers procedures for preparing and testing asphalt mixtures to measure thermal stress and strain and directly calculate: (1) the coefficient of axial thermal contraction, and (2) the modulus of asphalt mixture over a range of temperatures.
1.3 The procedure described in this standard provides required information for estimation of thermal cracking susceptibility of asphalt mixtures. The procedure applies to test specimens having a maximum aggregate size of 19 mm or less.
1.4 This standard can be used for conventional and nonconventional asphalt mixtures including but not limited to: hot asphalt mixtures, asphalt mixture with recycled materials, cold asphalt mixtures, warm asphalt mixtures, and neat or modified asphalt mixtures (for example, polymer or rubber-modified).
1.5 This standard can be used to determine the following:
1.5.1 Thermal stress buildup in asphalt mixture during a single cooling event.
1.5.2 Thermal strain in asphalt mixtures as a function of temperature.
1.5.3 Coefficient of axial thermal contraction.
1.5.4 Modulus of asphalt mixture as a function of temperature.
1.5.5 Thermal viscoelastic properties of asphalt mixture: viscous softening, viscous-glassy transition, glassy hardening, crack initiation, fracture temperature, and fracture stress.
1.5.6 UTSST cracking resistance index (CRI).
1.5.7 UTSST CRI adjusted for environmental condition (CRIEnv).
1.6 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 The text of this standard 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 standard.
1.8 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.
1.9 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.
