ASTM D8225-19 PDF Download

The ASTM D8225-19 standard is titled "Standard Test Method for Determination of Cracking Tolerance Index of Asphalt Mixture Using the Indirect Tensile Cracking Test at Intermediate Temperature." This test method is used to determine the cracking resistance of asphalt mixtures at intermediate temperatures, typically ranging from 5 °C to 35 °C, depending on local climate conditions.

The test specimens are obtained from Superpave gyratory compactor compacted cylinders or field cores, without the need for any cutting, gluing, notching, drilling, or instrumentation. The cracking tolerance index (CT Index) of an asphalt mixture is calculated based on the failure energy, the post-peak slope of the load-displacement curve, and the deformation tolerance at 75% of the peak load. The CT Index serves as a performance indicator for evaluating the cracking resistance of asphalt mixtures containing different components such as asphalt binders, modifiers, aggregate blends, fibers, and recycled materials. A higher CT Index value indicates better cracking resistance and less cracking in the field.

The standard emphasizes that the acceptable CT Index range may vary for different mix types and specific applications. It is recommended to use the CT Index and associated criteria during mix design and production quality control/assurance to identify mixtures prone to cracking. Note 1 in the standard highlights the importance of competent personnel, proper equipment calibration and maintenance, and adherence to relevant specifications for obtaining reliable test results.