Deconvoluting the Mechanisms of Thermal Degradation and Oxidation during the Aging Simulation of Elastomeric Modified Asphalt Binders

Abstract

Developing new and efficient methods to simulate the aging of asphalt binders and mixtures continues to be an important area of research for the asphalt community around the world. Temperatures exceeding pavement service temperatures are typically used to accelerate and simulate long-term aging in laboratory settings. However, it is unclear whether the use of such higher temperatures would have an adverse influence when simulating the aging of typical polymer modified binders. Specifically, the influence of thermal degradation of polymers at elevated temperatures and the resulting deterioration of the aging-related properties of the asphalt binder could be unrealistic when considering polymer degradation in the field. This study explores the use of an oxidative and nonoxidative environment to deconvolute the different aging characteristics of unmodified and styrene butadiene styrene (SBS) modified asphalt binders. Six binders, including two unmodified binders and four SBS-modified binders with two polymer contents (3% and 4.5% binder weight), were aged in two different aging conditions, i.e., under an air blanket and nitrogen blanket, at a temperature of 100°C. The resulting changes in material behavior were investigated using thin film poker-chip testing, dynamic shear rheometer testing, and Fourier transform infrared spectroscopy. Overall, the results from this investigation suggest that long-term aging of asphalt binders or mixtures conducted using temperatures not exceeding 100°C does not result in any significant degradation of polymers in modified asphalt binders.