Morphological and Nanomechanical Characterization of Industrial and Agricultural Waste–Modified Asphalt Binders

Abstract

For the past several decades, researchers around the world have used nanoindentation techniques to characterize different materials for biological, medical, and polymer science applications. In recent years, nanoindentation techniques have been explored by some pavement professionals to characterize asphalt materials. This study used the atomic force microscope (AFM)–based PeakForce quantitative nanomechanical mapping (PFQNM) technique to evaluate nanoscopic properties of asphalt binders modified with four different types of industrial and agricultural waste materials, which included ground tire rubber (GTR), reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAS), and rice husk ash (RHA). Three scan sizes (20 × 20, 10 × 10, and 5 × 5 µm) were used to map the properties of the aforementioned binder samples. Mechanistic properties such as adhesion, energy dissipation, deformation, and Derjaguin, Muller, and Toropov (DMT) moduli of modified binder samples were estimated at different morphological phases. The PFQNM analyses revealed distinct microstructures and grain distributions among tested additive-modified binder samples. The GTR-modified samples exhibited two distinct phases, namely, Catana and Peri phase, but the other additives provided another called the Perpetua phase. Mechanistic properties of the asphalt samples in the Catana and Peri phases were found to be similar but different for the Perpetua phase. The DMT moduli varied from 70 to 800 MPa, and the adhesion ranged from 8 to 12 nN. Among the four additives, RHA reduced the hardness of the asphalt binder unlike the others. The dissipation energy of the binder samples was found to be related to the adhesion, whereas the hardness depended on the depth of deformation. Demonstrations of quantitative mappings of the nanomechanistic properties of asphalt binders are expected to help build an understanding of the underlying sciences.