Abstract
This paper investigates the change in micromorphology of two binders and their respective warm mix asphalt binders before and after aging using atomic force microscopy (AFM) and optical microscopy. The control (PG 64-22) and crumb rubber modified (CRM) binders were blended with two different types of wax additives (L, a wax-based composition including crystal controller, and S, a long chain aliphatic hydrocarbon) and then artificially short-term and long-term aged using the rolling thin film oven and pressure aging vessel procedures. L is a wax based composition including crystal controller and S is a long chain aliphatic hydrocarbon. The AFM tapping-mode imaging technique was used to analyze the microstructure and the Superpave asphalt binder test was used to measure the rheology properties. In general, the results of this study indicated that (1) a correlation was observed between the changes in micromorphology (the distribution of dispersed domains and matrix) and rheology properties regardless of the aging, binder, and wax types; (2) the addition of crumb rubber into the base binder decreased the dimension of the catana phase (“bee-like”) structure, which increased the quantity of these structures; (3) the opposite trend was found between the aged control binder and the aged CRM binder regarding the size of the bee-like structure; (4) the long-term aging seemed to have a significant effect on the microstructures of the warm control and CRM binders; and (5) the inclusion of S and L was observed to have a similar trend for both binder types in terms of increased size of the bee-like structure and no bee-like structure, respectively.