Reclaimed Asphalt Pavement - Virgin Binder Diffusion in Asphalt Mixes

摘要

An important factor when Reclaimed Asphalt Pavement (RAP) is considered for new hot mix asphalt is the blending between RAP and virgin binders to ensure pavement resistance to moisture damage, permanent deformation, and cracking. It is shown, that RAP-virgin binder diffusion in RAP mixes follows the same scientific concept as observed previously for extracted RAP-virgin binder diffusion alone. The diffusion takes considerable amount of time even at elevated temperature. Nevertheless, virtually all RAP binder can be homogenized with virgin binder. A simulation of diffusion during realistic mix production, storage, and paving temperatures was performed. It was demonstrated that binder diffusion may not be completed by the time the pavement construction is completed. Low extent of blending between RAP and virgin binder can result in lower mix stiffness when compared to that expected based on blending charts in AASHTO M 323. Prolonged silo storage at elevated temperature can assist binder blending, however, mix hardening due to binder oxidation, evaporation and aggregate absorption can be significant. The outcomes of the study are based on laboratory testing of small mix specimens. Due to high variability of testing, the conclusions from this study should be verified for variety of mix designs and eventually by a field study.