Chemical and mechanical analysis of VAPro-aged asphalt binders from different crude oil sources

Abstract

Asphalt binders change their properties over time under natural and anthropogenic influences since they are of organic origin. This leads to a deterioration of the mechanical behavior and, thus to higher stiffness and brittleness of the binder. This phenomenon is commonly known as “aging.” As a consequence, these changes have a negative impact on the low temperature and fatigue behavior of asphalt mix layers. The standardized RTFOT for STA and PAV for LTA are used to simulate aging in the laboratory on the bitumen scale. On the asphalt mix scale, various methods have been developed for either loose material or compacted specimens. This paper presents a recently developed conditioning method called the “Viennese Aging Procedure” (VAPro) for long-term aging of compacted HMA specimens at close-to-field conditions (T = 60°C and p ≤ 1 bar). Air enriched with traces of highly oxidizing gases (ozone and nitrogen oxides) is passed through the specimens to enhance the oxidation reaction. The chemical reactions triggered by VAPro are expected to be similar to field aging. The applicability of the method is demonstrated. Mixtures containing four binders of the same grade were aged. Significant differences in aging behavior can be observed. The VAPro-aging is about 1.2 to 2.6 times stronger than that of PAV in terms of stiffness increase on the binder level. The mechanical analysis is extended with FTIR measurements. It is shown that this method is of great use in evaluating aging behavior and detecting poorly performing binders.