Investigation of Laboratory Aging Effects on Nanoclay-Modified Asphalt Binders

Abstract
Asphalt binder aging is recognized as a complex phenomenon that can significantly reduce the serviceability of flexible pavements. To address this issue, the aging behaviour and rheological properties of asphalt binders can be improved through asphalt binder modification. In this regard, the use of nanotechnology and nanomaterials are among the promising approaches for this purpose. The main objective of in this paper is to investigate the use of two types of Organo-Montmorillonite nanoclays with different dosages (2% and 4% by weight of asphalt binder) for enhancing the aging resistance of asphalt binders. Nanoclay-modified asphalt binders are prepared using a high shear mixer at 130±2 °C for 2 h at 3,000 rotations per minute. Initially, for the purpose of evaluating the material properties, various tests are applied to the unmodified and nanoclay-modified binders. The performance grades of the unmodified and modified binders are also investigated. Moreover, by examining the evolution of the fractions (i.e., saturates, asphaltenes, resins, and aromatics) the colloidal index is calculated and the storage-stability of the nanoclay-modified binders is analyzed accordingly. The asphalt binders modified with 4% nanoclays are found to have the best storage-stability among the evaluated binders. After characterizing the unaged properties, rolling thin-film oven (RTFO) aging was carried out for 85 minutes at 163 °C, followed by aging in pressure aging vessel (PAV) for 20 h under 2.1 MPa pressure at 100 °C. Using a dynamic shear rheometer, the complex shear modulus (G*) and phase angles (δ) of the binders were determined at different temperatures and loading frequencies before and after aging. Finally, based on the aging indices, the impact of nanoclay modification on the aging resistance of asphalt binders was investigated. The results of this study showed that nanoclay modification can mitigate the impact of aging on asphalt binders compared to the unmodified binder.  

Keywords: Asphalt binder aging; Binder modification; Nanoclay, Rheology; Aging indices.