Quantification of oxygen uptake enabled by temperature- and pressure-corrected oxidation stability tests — Application to assessment of aging susceptibility of bitumen

Abstract

Oxygen uptake of materials, such as e.g. during the aging of process bitumen at environmental conditions, effects the mechanical properties and, hence, technical usability. For assessing the kinetics of such processes and finally predicting the serviceability of materials, quantitative experimental methods are required for identifying the underlying kinetic behavior. In the present contribution, an oxidation stability test device enabling the continuous measurement of the oxygen uptake by the considered material sample is employed. This method allows to expose material samples to certain gas pressures and temperatures for artificial acceleration of the oxygen uptake, simultaneously accessed by recording the decrease of pressure. Even though this method has already been successfully employed for analyzing the oxidation stability of various materials, its application to quantitative analysis on a wider time scale comprising short-term as well as long-term behavior requires correction procedures for the temperature and pressure history, which are outlined in the present paper. The method is applied to bitumen samples at different temperatures, providing quantitative access to the underlying aging kinetics, with respective changes within the sample materials being complementarily assessed by Fourier-transform infrared spectroscopy (FTIR). Finally, options and limits for simplified data-analysis procedures for oxidation stability test results are discussed.