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As binder aging plays a significant role in the durability and performance of asphalt pavements, it is important to understand and quantify the effects of aging. A first objective of this study is to compare accelerated aging versus aging under more realistic conditions. Bituminous binders were aged using various procedures, in a first procedure, binders were aged outdoors in such a way that a maximum exposure to direct sun radiation was obtained. In a second procedure, samples were also outdoor aged, but without direct exposure to sun radiation. In a third experiment binders were aged indoors at ambient conditions initially with exposure to sun radiation, and also without exposure to light (dark aging). Finally binders were aged in the pressure aging vessel(PAV) under standard conditions.
As expected, and as is known in literature for a long time, under field conditions bitumen ages more severe at the top surface compared to the bottom surface. The tests for the samples aged under ambient conditions show that bottom surfaces were almost unchanged, while top surfaces showed significant changes in the spectrum, with the formation of a lot of polar groups. On the other hand, for the samples aged in the PAV, the aging was rather homogeneous through the thickness of the binders and the changes in the spectrum due to aging were much smaller. The amount of carbonyl groups after PAV aging at 100°C, 20 hours, is identified on the surface of samples aged at ambient temperature already after a few days. The tests also show clear differences in the FT-IR spectra, depending on whether the binders were exposed or not exposed to sun radiation. The dark aged binder surface (no exposure to light, only to air) also changed with time. In this case, the formation of alcoholic functional groups was quite clear, with almost no formation of carboxylic groups.
Hilde Soenen, Serge Heyrman, Xiaohu Lu, Per Redelius
ISAP conference 2012