科研之友
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摘要
In this work, studies were performed in Brazilian asphaltic cements by separating fractions of maltenes and asphaltenes using nonaqueous ion exchange liquid chromatography (NIELC). Initially, three different aging processes (RTFOT, PAV, and SUNTEST) were applied to 23 different asphaltic cements for evaluating the changing of asphaltenic (12.7 +/- 2.5%) and maltenic (90.6 +/- 5.0%) compounds. The RTFOT+SUNTEST process was studied in a comparative way for 5 asphalt cements samples, since it caused the more pronounced changes in maltenes and asphaltenes among the asphaltic cements supplied by different Brazilian refineries. Asphaltenes presented the highest amount of polar compounds in all the studied samples, herein attributed to compounds of acidic and basic character that contain sulfur. It was also found that the aging of asphalt cement leads to an increase of the more reactive acidic (9.5-18.9%) and basic (14.6-30.9%) fraction in both asphaltenes and maltenes. As a result, a reactivity index (Ir) for asphaltic cements was calculated and proposed for classifying the studied samples regarding their aging susceptibility. It was also observed that the less reactive asphaltic cement presented the highest amount (>80%) of neutral sulfur compounds in maltenic fraction. Lastly, it was concluded that a higher content of total sulfur in asphalts does not imply necessarily in a higher chemical reactivity (susceptibility to aging) of the cement, as observed for 5 studied samples having total sulfur ranging from 1.8 to 3.4% (w/w). The presence of functional groups related to their specific heteroatoms, such as sulfur, suggest a possible way to explain a greater or lesser susceptibility of asphalts to aging.
- 出版日期2015-3
