Use of fracture work density obtained from indirect tensile testing for the mix design and development of a fatigue model

Abstract

Bottom-up fatigue cracking, which is a major distress in asphalt pavements, is due to repeated traffic loading that induces tensile stress in the asphalt concrete layers. Fatigue cracks are observed as interconnected cracks in the wheelpath of asphalt pavements. Fatigue cracking can and should be addressed during both the mix design and pavement design. Therefore, a performance indicator is needed during the mix design to select a fatigue-resistant mix. In addition, a fatigue model, which includes the performance indicator, is needed to design the pavement structure. This study is conducted to determine a performance indicator for fatigue and to develop a new fatigue model, based on the Federal Highway Administration's Accelerated Load Facility experiments on fatigue. It is found that the fracture work density (FWD) obtained from indirect tensile testing correlates highly with field fatigue performance, whereas fracture energy fails to correlate with field fatigue performance. A new fatigue model based on FWD is developed herein and is found to be effective in characterising field fatigue performance. Further study is needed to validate the effectiveness of FWD and the new fatigue model.

Keywords:

• fatigue
• fracture work
• fracture energy
• model
• dynamic modulus

Acknowledgements

The author wishes to thank the FHWA, especially Dr Nelson Gibson and Dr Emin Kutay of Michigan State University for sharing the data, without which this study could not have been completed.