Influence of reactive oxygen species and humidity on binder aging under direct and indirect exposure

Abstract

The aging of bituminous binders is a complex process that is influenced by a number of environmental factors including temperature, sunlight, humidity and reactive oxygen species (ROS) found in the troposphere. The effect of two of these factors, humidity and reactive oxygen species (ROS), are investigated in an environmental aging setup called the Viennese Binder Aging (VBA) method. Three unmodified and one polymer modified binder (PmB) were aged under conditions of varying duration (2 and 3 days), water exposure modes (direct versus indirect) and humidity levels. Additionally, experiments were conducted without the incorporation of ROS. Fourier transform infrared (FTIR) spectroscopy and Dynamic Shear Rheometer (DSR) were used for analysis. One binder showed accelerated aging due to the combination of ROS and humidity. Furthermore, a marginal increase in polybutadiene degradation due to humidity was detectable. However, when ROS were removed from the test setup, increasing the humidity levels did not increase the aging of any of the binders. The fact that the synergistic effects of humidity and ROS only affected the aging of one of the binders shows the complexity of this matter and highlights the importance of incorporating environmental factors into laboratory aging.