Impact of aging protocols on asphalt binder behavior: A laboratory and field study

Abstract

In this study, the focus was on the analysis of asphalt binder aging, a complex process that induces physical, chemical, and rheological changes in these materials, affecting the performance of asphalt mixtures over time. While thermal-oxidative aging is well-documented, the aspects of photo-oxidative aging and the influence of moisture are frequently overlooked. The investigation assessed 50/70 asphalt binder that underwent short-term and long-term aging in both laboratory and field climatic conditions in Brazil. Initially, these binders underwent short-term aging using the Rolling Thin-Film Oven (RTFO) method. Subsequently, the binders were subjected to prolonged aging, exposing them to heat, oxygen, UV radiation, and moisture. The chemical results unveiled distinct reaction mechanisms during thermal and photochemical aging processes. Greater oxidation was observed when binders were exposed to UV radiation, while the oven protocol resulted in increased binder stiffness. Following prolonged aging, a noticeable increase in binder stiffness was observed, particularly when exposed to a temperature of 85 °C. Concurrently, a decrease in fatigue resistance at high strains and a reduction in permanent deformations were identified after aging. The effects of UV radiation were less pronounced than anticipated, mainly due to the lower chamber temperature (60 °C). Nevertheless, the applied stimuli expedited the aging process, underscoring the significance of including UV radiation and moisture in laboratory aging studies. Additionally, it was observed that the aging protocol at 85 °C yielded results analogous to those observed under field conditions over a six-month period in the northeastern region of Brazil.