The design and use of antioxidant additives to reduce or slow down the aging of asphalt binders can bring about tremendous benefits to the asphalt industry. Despite many isolated and scattered research efforts showing mixed results, the application of this science to engineering-based solutions has been limited due to variability in results and conflicting data available. This work presents the results from a global interlaboratory study to test the effectiveness of promising antioxidant additives, namely kraft lignin, calcium hydroxide, zinc diethyldithiocarbamate and phenothiazine to increase the resilience of asphalt binders and provide insights towards understanding the complex intricacies between chemistry and rheology. Specifically, seven different binders from various geographical regions in the world i.e., Texas (USA), Vienna (Austria), Illinois (USA), Antwerp (Belgium), and Delft (Netherlands) were blended with the antioxidants at two proportions. Subsequently, the chemical and rheological properties of the blends were evaluated using Fourier transform infrared (FTIR) spectroscopy and dynamic shear rheometer (DSR). The results indicate that although some antioxidants may reduce oxidation based chemical indices, their effect on rheology is more complicated and possibly related to unique physicochemical interactions in each binder. From a macro-perspective, zinc diethyldithiocarbamate showed promising results with a good correlation between rheology and chemistry for the majority of the binders. These additives or other additives with the same working principles should be investigated further. Additionally, significant research efforts must also be directed towards approaches aimed at understanding mechanisms of interaction and relating results with specific binder compositions.@en

With the effort to precisely predict the lifetime of asphalt binders and subsequently optimize their utilization in a more economical way, the objective of this study was to introduce a new methodology to improve the fatigue characterization of asphalt binders through a new dynamic shear rheometer (DSR) sample testing geometry. Initially, numerical analyses were performed to study the geometry-related issues of a standard DSR sample on time sweep tests, and to assist in the effort to increase understanding of the DSR damage phenomena of asphalt samples. On the basis of these numerical analyses, a new testing geometry, the parallel hollow plate, was developed and its test results compared with the standard sample testing geometry. A single type of asphalt binder was assessed using amplitude sweep tests. The obtained results demonstrated a significant difference between the fatigue of the two sets of DSR sample geometries. On the basis of these, time sweep tests were conducted for the same sample geometries and the results demonstrated that the new testing geometry yields material response consistency under different loading conditions. The lifetime prediction of the standard parallel plates showed a significant difference with the newly developed DSR sample testing geometry by overestimating the total number of cycles until asphalt binder failure. The new testing geometry allowed the isolation of the damaged area of asphalt binder by localizing the shear stresses in the samples’ periphery.

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