Characterization of Asphalt Materials for Moisture Damage Using Atomic Force Microscopy and Nanoindentation

Abstract

Asphalt materials have traditionally been characterized for moisture damage at component (microscale) and laboratory specimen (macro) scales. Though characterizations at such scales are commendable and often necessary and well understood by the pavement engineering community, there are problems which cannot be solved using micro and macroscale characterizations. For example, moisture damage in asphalt pavement is caused by moisture interaction with asphalt-aggregate bonds, which occurs at the atomic or nanoscale level. Macro and microscales scales are inadequate for developing an understanding of the bond damage phenomena. As a result the moisture damage still remains as one of the most common but complex problems of asphalt concrete. This chapter describes the use of Atomic Force Microscopy (AFM) and nanoindentation techniques to gain accurate insight into moisture damage performance of asphalt materials at nanoscale. In particular, moisture damage is quantified in performance grade (PG) asphalt binders using AFM measured adhesion values. It is shown that a PG 76-28 binder is more resistant to moisture damage than a PG 70-22 binder. Using nanoindentation, it is shown that hardness increases due to wet conditioning of aggregate, whereas hardness decreases due to wet conditioning of mastic, which is a mixture of fines and asphalt binder. Modulus value measured by nanoindenter did not show any tend due to wet and dry conditioning. It is hoped that pavement materials engineers and researchers benefit from the nanoscale characterization presented in this chapter.