Asphalt Binder Laboratory Short-Term Aging: Effective Parameters and New Protocol for Testing

Abstract

This work addresses the effect of time, temperature, airflow rate, and weight of asphalt binder on the laboratory short-term aging of asphalt binders and proposes an alternative protocol that can reduce the aging time and resolve some of the current short-term aging protocol shortcomings. In the first part of this study, two asphalt binders from different sources were examined in a rolling thin-film oven at different combinations of the aforementioned test parameters. The high-end continuous performance grading temperature and carbonyl index were considered as the two responses for quantification and qualification of laboratory aging. The statistical analysis showed that the first-order terms of time, temperature, and weight as well as their interactive terms were statistically significant. However, the effect of airflow rate within the studied range was insignificant. Based on the findings of the first part of study, an alternative protocol was proposed for the study of short-term aging in a rolling thin-film oven. One unmodified and three highly modified binders were aged in a rolling thin-film oven under the current and proposed aging conditions for comparative purposes. According to the obtained rheological properties (high- and low-end continuous performance grading temperature and viscosity) as well as the chemical characteristics (carbonyl index, saturate-aromatic-resin-asphaltene fractions, and oxygen content), it was shown that the proposed laboratory short-term aging protocol not only can reduce the aging time of the conventional protocol, but also that it is applicable to both unmodified and polymer-modified asphalt binders.