Effect of aggregate contact condition on skeleton stability in asphalt mixture

ABSTRACT

To investigate the effect of aggregate contact condition on the deformation stability of asphalt mixture (DSAM), computed tomography system was used to acquire a contact parameter of aggregates – the aggregate contact index (ACI) characterising the contact characteristic for coarse aggregate. The aggregate slip tests were conducted under different test conditions . This paper investigates the relationship between ACI and slip energy index (SEI), and discusses the effects of aggregate-asphalt combined action and aggregate gradation on DSAM. The results indicate that SEI shows a good relationship with ACI. At 60 °C, SEI has the best linear correlation with the parameter ACI*VFA (Voids Filled with Asphalt), and the deformation stability has the biggest increase amplitude with the increase in ACI*VFA. In the high-temperature range (higher than 50 °C), there is a good linear relationship between SEI and ACI/VFA, and the contribution of aggregate contact to DSAM is bigger under a higher temperature. However, the action of asphalt changes to lubrication from cementation with the increase in temperature, so the growth of SEI with ACI/VFA becomes smaller. AC-13b mix has a better deformation stability than AC-13a and AC-13c mixes at 60 °C though they have the same nominal maximum aggregate size.

KEYWORDS:

• Asphalt mixture
• aggregate contact condition
• skeleton stability
• slip energy index (SEI)
• skeleton contact index (ACI)

Additional information

Funding

This work was supported by Applied Basic Research Project the Ministry of Transport of China [grant number 2014319812151]; Natural Science Basic Research Plan in Shaanxi Province of China [grant number 2014JQ7242]; the Special Fund for Basic Scientific Research of Central Colleges [grant number 310821162010], [grant number 310821163404]; the National Natural Science Foundation of China [grant number 51008031].