Micromorphology and Rheology of Warm Binders Depending on Aging

Abstract

In this paper, the micromorphology of asphalt binders with wax warm additives is investigated by atomic force microscopy (AFM) and optical microscopy before and after aging. Performance grade (PG) 64-22 asphalt binder is used to produce warm mix asphalt binder containing two wax additives, LEADCAP and Sasobit, and then the warm binders are artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Microstructure and rheology properties of the binders are characterized using AFM tapping-mode imaging techniques and the Superpave asphalt binder test, respectively. The results of this study indicate that (1) the wax type and aging level have a significant effect on the micromorphology of the binders; (2) the binders with LEADCAP exhibit no “bee-like” structures; (3) the addition of Sasobit into the binder increases the dimension of the bee-like structures regardless of the aging level and binder types; (4) the dispersed domain has higher stiffness than does the para phase; (5) the aging of the binders increases the bee shape but reduces the number of the structures; (6) the expanded peri phase is observed after the aging; and (7) the binder roughness increases after aging and shows a good relationship with the stiffness results.