Microstructural analysis of the effects of compaction on fatigue properties of asphalt mixtures

ABSTRACT

In the current approaches to structural analysis for asphalt pavements, the entire pavement material is usually treated to identical material, which disregards the distinct heterogeneity of asphalt mixture. Asphalt mixture is actually a multi-phase heterogeneous material that is composed of air voids, aggregate and asphalt binder. In this study, asphalt specimens were drilled from a test track and the indirect tensile fatigue test was conducted to study the fatigue properties. Digital Image Processing (DIP) was used to investigate the microstructural changes of the asphalt specimens based on X-ray Computed Tomography (X-ray CT) images. The aggregate orientation and number of aggregate contact points were determined. The distribution of the air-voids content and shape index of air voids before and after the fatigue tests were comprehensively discussed. According to the results, the microscopic analysis can effectively predict the evolutions of the internal structures of asphalt mixtures during fatigue damage. The heterogeneity due to different degrees of compaction significantly affects the fatigue properties of the asphalt mixtures. This study not only provides support for the further research on the relationship between the microstructural characteristics and mechanical damages of asphalt mixture but also provides implications for conducting the structural mechanical analysis of asphalt pavement.

KEYWORDS:

• Asphalt mixture
• X-ray computed tomography
• compaction
• fatigue damage
• microstructural characteristics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This paper is based on a part of a research project carried out at the request of the National Key Research and Development Program of China (grant number 2018YFB1600100), German Research Foundation (Deutsche Forschungsgemeinschaft – DFG, grant number OE 514/1-2 of FOR2089) and German Academic Exchange Service (Deutscher Akademischer Austauschdienst – DAAD, grant number 57446137 under Australia-Germany Joint Research Co-operation Scheme, cooperation with Dr Xu Yang). The authors are solely responsible for the content.