Immediate and Long-Term Characteristics of Recycling Agents in the Restoration of Chemical Properties of Aged Asphalt Binder

Abstract

The aging of asphalt binder is one of the most serious problems related to using binder in asphalt pavement. Therefore, understanding the effect of aging on the chemistry and rheology of asphalt binders is important to achieve proper durability and longevity in asphalt pavement design. The chemical properties of asphalt binder and the ratio of maltenes to asphaltenes change during the aging process. Many studies have investigated the immediate effect of recycling agents (RAs) on aged binder properties, but understanding the behavior of restored binders in the next period of pavement service is quite limited. This study aims to evaluate the immediate and long-term influence of different RAs in restoring the chemical properties of aged asphalt binders. Three different types of RAs, namely aromatic extracts, paraffinic oil, and naphthenic oil, were used to modify the blended binder in this study. The chemical properties of the modified blended binders were characterized by a saturates-aromatics-resins-asphaltenes (SARA) fractionation analysis, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and elemental (carbon, hydrogen, nitrogen, sulfur, and oxygen) analysis. The results indicated that RAs have restored the chemical and microstructural properties of the aged binder. The relatively limited increase in colloidal index (CI) due to aging in the restored binders indicated that the RAs have performed well in maintaining the stability of the colloidal structure of binder in the long-term aging. Paraffinic oil performed better than the other two RAs in maintaining the chemical composition and colloidal stability of binder.