Comparative Evaluation of Flow Number (FN) and Permanent Flexural Microstrain (PFM) of Asphalt Concrete (AC) under Dynamic Flexural Stresses (DFS) and Hamburg Wheel Tracking Test (HWTT)

Abstract

Monitoring the variation in FN and PFM within the AC structure after recycling of RAP is a sound start for the evaluation of the quality of the recycling process. The FN of AC is an important variable since it correlates well with the rutting potential of AC pavement. In the present assessment, slab samples of roller-compacted AC (RAP and recycled with soft binder) have been prepared. Part of the slab samples were tested for permanent deformation (PD) and FN with HWTTAC at a 60° C environment. Beam specimens were obtained from the other part of the prepared (RAP and recycled) AC slab samples and tested for PFM and FN using the pneumatic repeated load system under constant stress at 20° C. The FN increased by 100 % after recycling, while the PD increased by fourfold at failure when the test was conducted under DFS. The HWTT indicated that the FN of AC after recycling declined by 25 % when compared with that of the RAP mixture. However, the PD of recycled AC at failure is higher than that of the RAP mixture by 200 %. Power mathematical models were obtained representing the rate of change in the FN of the AC mixture through fatigue life (FL) due to recycling with a soft binder. The obtained mathematical power regression models exhibited high coefficients of determination, which can provide a rough guide to be implemented for preliminary estimation of the quality of recycled RAP within the investigated material properties.