Influence of thermal aging and long term-aging on Ni and V content in asphalt fractions and their determination in air particulate matter from asphalt mixing plants

Abstract

Ni and V can contribute to the deterioration of asphalt pavement by catalyzing the oxidation of some organic molecules present in the binder structure. In this work, the influence of the aging process on Ni and V compounds was studied by comparing the concentration of these two metals in the maltenic and asphaltenic fractions of virgin and aged asphalts. Long-term aging process was simulated by the combination of the rolling thin film oven test (RTFOT) and the SUNTEST method. The results showed that up to 56% of Ni and 53% of V were lost after aging. The greatest changes were observed for the acidic subfraction of both maltenes and asphaltenes. RTFOT/SUNTEST process was also compared to thermal aging using an extraction and collection device (DEC). All V losses were due to the emission of its volatile compounds during thermal aging. Ni losses were attributed to both UV–VIS radiation and sample heating. The presented results help to understand the behavior of both metals during asphalt aging, which has important economic value and can be useful to find solutions that delay the aging process. Ni and V were also determined in the organic fraction of air particulate matter from two asphalt mixing plants. Concentrations of Ni and V ranged from 0.42 to 0.84 ng m−3 h−1 and from 0.08 to 1.79 ng m−3 h−1, respectively, showing that the production of asphalt mixtures can contribute to the air pollution through the emission of Ni and V compounds.