Effect of freeze-thaw cycles on the resilient moduli and permanent deformation of RAP/natural aggregate unbound base mixtures

This paper presents an experimental study to evaluate the effect of freeze-thaw cycles on the resilient modulus and permanent deformation of reclaimed asphalt pavement (RAP)/natural aggregate mixtures for the construction of unbound base layers. A repeated load triaxial test was carried out on RAP and crushed limestone mixtures with varying RAP content (0%, 20%, 35%, and 50% of dry mass), on both standard samples and samples exposed to fourteen freeze-thaw cycles. Freeze-thaw conditioning resulted in a decrease of resilient modulus values and an increase of permanent deformation. This trend was most pronounced on the mixture with 0% RAP. Mixtures with 35% RAP exhibited stable resilient behavior and lowest change in accumulation of permanent deformation after freeze-thaw conditioning. With an increase in RAP content, the sensitivity of the mixtures to freeze-thaw cycling in regards to resilient and permanent deformation behavior is reduced, but only up to a certain RAP content.