Impact of rest period on asphalt concrete permanent deformation

Truck platooning has several advantages including congestion reduction, safety, and fuel efficiency. However, there are concerns regarding its impact on pavement performance due to channelized traffic and reduced spacing. A rest period governed by the distance between each truck can have a significant impact on asphalt pavement performance due to time dependent deformation characteristics of asphalt materials. Despite numerous studies available in the literature explaining the rest period effect on fatigue cracking, the impact on permanent deformations is relatively less studied. In this paper, we present the results to characterize the impact of rest period on the permanent deformation characteristics of two asphalt concrete (AC) mixes using four different types of binders. The experimental program included repeated load permanent deformation experiments coupling rest period with various stress and temperature configurations. Increasing rest periods from 0.18 s to 2.5 s increased permanent deformations consistently for the two mixes. The results are consistent with the hardening-relaxation or hardening–softening mechanisms describing the reorientation of the aggregate structure from a more resistant to less resistant state to deformations as rest duration increases. It was also shown with the customized multiple stress creep recovery experiments that the effect of rest period on mixture level permanent deformations could not be attributed to the binders’ deformation characteristics. Rest period impact was found to be as important as temperature and stress magnitude for asphalt mixture's permanent deformation resistance. Various truck platoon scenarios can be compared to conventional truck configuration and loading assumptions using the results presented in this paper.