Comparison of Chemical and Microstructural Properties of Virgin and Reclaimed Asphalt Pavement Binders and Their Saturate, Aromatic, Resin, and Asphaltene Fractions

Abstract

The chemical properties and microstructural features of two straight-run virgin asphalt binders (PG 52-34 and 58-28) and a reclaimed asphalt pavement (RAP) binder as well as their corresponding saturate, aromatic, resin, and asphaltene (SARA) fractions were examined. Additionally, the properties of the binders with laboratory and plant mixture blending were also observed. Examining the corresponding SARA fractions revealed that the increases in the carbonyl index of RAP relative to the virgin binders were mainly found in the resin and asphaltene fractions, while the increase in the sulfoxide index is mainly found in the asphaltene fraction. The chemical properties were examined using Fourier transform infrared spectrometry. The RAP binder showed a significant increase in the indices of the carbonyl (I_C=O) and sulfoxide (I_S=O) functional groups compared to the virgin binders. The plant blended binders showed that additional silo storage at the plant increases the carbonyl index. The microstructural features of the binders were examined using environmental scanning electron microscopy (ESEM). The fibril microstructure of the virgin binders was found to be relatively sparse. On the other hand, this microstructure was not visible in the RAP binder, possibly as a result of the severity of the aging, with a severly aged blended binder structure only becoming visible at higher irradiation intensity. The ESEM observation of the resin and naphthene aromatic fractions did not reveal a fibril microstructure as it did in the binders.