Impact of Aging on Molecular Structure of Asphalts from Different Crude Oils

This research aimed to explore the impact of aging on the molecular structure of asphalts from different crude oils. The elemental composition of five types of original asphalts was measured. The structure changes of the asphalts were analyzed with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) before and after thin-film oven test, ultraviolet light (UV), and pressure aging vessel (PAV). The result of the elemental analysis showed that the hydrogen-carbon ratio (H/C) of asphalts ranges from 1.347 to 1.602 with different contents of sulfur, nitrogen, and oxygen. The FTIR indicated that asphalts with a low H/C had a low rate of change of carbonyl index after aging. Asphalts were more likely to produce an aromatic ring structure and sulfoxide group during the PAV aging process. The aliphatic structure was easier to reduce during the UV aging process. The 1H-NMR analysis showed that the content of aromatic hydrogen (Har) of asphalts is between 0.022 and 0.056, the content of Har decreased after aging, and the asphalt with a low Har content had a smaller change rate of hydrogen atom content. The outlined research results revealed that the asphalt with lower H/C and Har content was prone to have better aging resistance.