Microscopic examination of rejuvenated binders with high reclaimed asphalts

Abstract

A properly formulated rejuvenator is a possible remedy for asphalt pavements with a high percentage of Reclaimed Asphalt Pavement (RAP), which is traditionally too stiff to resist premature damage due to fatigue cracking. Rejuvenated asphalt binders with high RAP have traditionally been evaluated by micro- and macro-level test methods, which are transcendental in providing binders’ molecular level properties that govern their performance properties. This paper presents the usefulness of an Atomic Force Microscope (AFM) and its nanoindentation technique to observe morphological and nanomechanical properties of rejuvenated asphalt binders with high RAP. A commercial rejuvenator is applied in a Performance Grade (PG) (PG 64-22) binder blended with different percentages (25%, 40%, and 60%, by the weight of the blended binder) of a bulk RAP. The rejuvenated asphalt binder blends were subjected to routine tests such as Penetration, Rotational Viscosity (RV), and Dynamic Shear Rheometer (DSR) as well as the AFM-based PeakForce Quantitative Nanomechanical Mapping (PFQNM™) analysis. As expected, the routine test results reveal that the rejuvenator reduces the stiffness of the RAP-modified binders. The effects of rejuvenator on the RAP-blended binders are evident in the morphological images and nano-level mechanistic data. Based on the AFM test results, it is observed that modulus values of RAP blended binders reduced significantly when the rejuvenator was used. The findings of this study will benefit the pavement professionals for assessing the effectiveness of rejuvenators in asphalt binders with high RAP contents.