scope:

This test method covers the determination of cracking resistance of asphalt mixtures using the indirect tensile (IDT) geometry at 25℃. The Toughness (area beneath the stress-estimated strain data) and Brittleness Slope (post peak stress-estimated strain rate) are used to calculate a parameter referred to as the N_flex factor, which may be a useful indicator of load-related cracking of asphalt pavement layers.

This procedure applies to test specimens having a nominal maximum aggregate size (NMAS) of 19 mm or less. Lab compacted specimens or field core specimens can be used.

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 and follow appropriate health and safety practices and determine the applicability of regulatory limitations prior to use.

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 R 18 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with R 18 alone does not completely assure reliable results. Reliable results depend on many factors; following the suggestions of R 18 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.