The role of promising antioxidants in the chemomechanics of asphalt binders

Abstract

Oxidative aging of asphalt binder, is a well-recognized and omnipresent phenomenon that leads to several distress types. As an effective way to tackle it, antioxidants have been introduced in asphalt binders. Although it is well documented that certain antioxidants are effective in preventing the deleterious impact of aging on the physical and mechanical properties of asphalt binders, an in-depth investigation of their impacts on meaningful viscoelastic parameters is yet missing. Therefore, this paper examines two promising antioxidants, namely kraft lignin and zinc diethyldithiocarbamate at two different contents of 3% and 5% binder enhancement, utilizing distress-related rheological indicators. Among others, master curves, the Glover-Rowe and ΔΤc parameters were extracted from Dynamic Shear Rheometer, supporting in general a softening effect for zinc and a stiffening effect for lignin. Ultimately, this work seeks to shed light on the functionality of these antioxidants at the virgin asphalt binder state as well as to comprehensively assess their efficiency after laboratory short- and long-term aging compared to their unmodified counterparts. As such, a Relative Aging Index is introduced to fairly compare the aging capacity of the two antioxidants in all blends. Additionally, the rheological investigation is contrasted with aging-related functional groups via Fourier-Transform Infrared spectroscopy, and the findings indicate that there is sufficient basis for supporting a satisfying correlation between the Glover-Rowe parameter and the carbonyl index. Overall, this study dives into a detailed analysis of the rheological behavior of antioxidant-enhanced binders and provides confidence for the application of zinc on a wide scale.