Development of a rate-dependent cumulative work and instantaneous power-based asphalt cracking performance index

Abstract

Use of the semi-circular bending (SCB) test has gained popularity for evaluating cracking performance of asphalt mixtures. An Illinois Flexibility Index Test (I-FIT) variant of SCB has shown the ability to distinguish mixtures through use of the flexibility index (FI) parameter. While this index has been able to rank the mixtures with respect to performance, a high coefficient of variation (COV) among the replicates has often been observed. Furthermore, parameters such as total fracture energy and FI do not incorporate rate dependency of fracture processes which are very important for viscoelastic materials such as asphalt mixtures at low and intermediate temperatures. In light of these observations, a rate-dependent cracking index (RDCI) is proposed that utilises cumulative fracture work potential and instantaneous power calculated from the I-FIT test to assess impulse of the mixture. Thus, in spirit, this parameter captures the fracture energy and crack velocity of the material; however, these are calculated in a rate-dependent manner. A total of 18 surface course mixtures were analysed using the RDCI and resulted in an average overall reduction of 10.6% in COV as compared to FI while maintaining similar ranking of mixtures. In general, RDCI was able to better discriminate the 18 mixtures as compared to FI. The evaluation of five mixtures at three aging levels showed the robustness of RDCI in capturing effects of aging on fracture behaviour of asphalt mixtures.

Keywords:

• semi-circular bend (SCB)
• cracking
• flexibility index
• cumulative energy
• instantaneous power

Acknowledgements

The authors would like to acknowledge Brian Hill and Brian Pfeifer from the Illinois Department of Transportation (IDOT) for performing SCB testing as part of the National Road Research Alliance (NRRA) Long Term (LT1) project. Acknowledgments are also extended to the Transportation Pooled Fund project (TPF) 5(230) for all Virginia mixtures used in this study as well as the New Hampshire Department of Transportation for providing all NH mixtures. Thank you to Runhua Zhang from University of New Hampshire for conducting tests on aged mixtures.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Rasool Nemati http://orcid.org/0000-0002-5526-9838

Katie Haslett http://orcid.org/0000-0002-3494-1066

Eshan V. Dave http://orcid.org/0000-0001-9788-2246

Jo E. Sias http://orcid.org/0000-0001-5284-0392

Additional information

Funding

This work was supported by New Hampshire Department of Transportation: [Grant Number 26962N]; Minnesota Department of Transportation: [Grant Number 1003326-002].