Evaluation of degradation of polymer due to aging in asphalt binder using a novel and DSR-based extensional deformation test

Modification of asphalt binder is a must to improve the physical and rheological properties of asphalt binder and it is most commonly done by polymer addition. The objective of this study is to investigate the degradation of polymer in Polymer Modified Asphalt Binder (PMAB) due to aging by using a novel test method replacing force ductility test. PMAB PG 76–22 was artificially aged by Rolling Thin Film Oven (RTFO) for short term aging and Pressure Aging Vessel (PAV) for long term aging. Here, extensional deformation behavior of unaged PMAB, short term aged PMAB and long term aged PMAB were investigated through an extensional rheological approach using a DSR-based Sentmanat Extensional Rheometer (SER). Extensional tests were performed at three different temperatures: 0°C, 4°C and 12°C. The investigated parameters were first peak elongation force F₁, second peak elongation force F_2, ratio of second peak elongation force over first peak elongation force F₂/F₁. F₁ is not related to polymer property as it is observed for both unmodified and modified binders, rather it is a property of asphalt binder itself. F₂ is related to the polymer as it is observed for polymer modified binders only and it depends on the type and percentage of the polymer. It was found that F₁ increases after short term and long term aging. F₂/F₁ decreases after short term aging and it further decreases due to long term aging which is an indication that polymer in asphalt binder is degrading due to these aging processes.