Asphalt Binder Cracking Device to Reduce Low-Temperature Asphalt Pavement Cracking: Final Report
ABCD is an empirical test method evaluating the low-temperature performance of asphalt binder. The ABCD test method is simple and practical for estimating the cracking temperature of asphalt binder because it tests the samples under a field-like condition, eliminating the need for assuming and measuring several asphalt binder properties required in the theoretical calculation procedure.
The ABCD test method has been adopted as an AASHTO Provisional Standard. Provisional Standards are adopted as standards on a temporary basis for a maximum of 8 years and are reviewed every 2 years. At any time during the 8-year period, AASHTO can convert a Provisional Standard into a Full Standard. The ABCD is not intended to replace the current low-temperature binder grading specifications and test methods. Instead, the ABCD test method may be added to the currently available test methods for characterizing and grading asphalt binders at low temperatures.
Following are recommendations for the implementation of ABCD for prediction of low-temperature performance of asphalt binders.
- The relationship between the ABCD cracking temperatures of asphalt binders and the field performance of asphalt pavements should be determined for utilization of ABCD test results in the current asphalt binder low-temperature grading specifications. Though the properties of asphalt binder have the major influence, other variables, such as aggregate properties, mixture volumetrics, and pavement structure, also influence the low-temperature performance of asphalt pavement. A future study is needed to determine the ABCD cracking temperature and pavement low-temperature performance while controlling the effects of the aforementioned other pavement variables using laboratory and field samples with known performance data.
- The effects of isothermal conditioning (known as physical hardening) on the low-temperature performance of asphalt binders should be studied with the ABCD. The significant adverse effects of isothermal conditioning of certain asphalt binders on rheological properties(7, 8) and pavement performance(7) at low temperatures have been reported. However, when measured with the ABCD where the contraction of the test specimen was restrained during conditioning, the effects of isothermal conditioning on the ABCD cracking temperature were either adverse or beneficial depending on the asphalt binder type in the limited Phase 1 experiment.(5) A more comprehensive isothermal conditioning study using various binder types and asphalt mixes is needed.