Abstract
Observing the microstructure of bituminous binders with an environmental scanning electron microscope (ESEM) can contribute significantly to reveal the underlying rejuvenation mechanism. In this study, three rejuvenators were selected to regenerate the aged SBS modified binders at five dosages, and their rheology was evaluated using a dynamic shear rheometer. ESEM was employed to examine the microstructure of binders as well, and a series of microstructure parameters were quantified with image analysis. The results demonstrated that the chemical composition changes correspond to the evolution of microstructure morphological and rheological properties. Moreover, the rheological and microstructure characteristics were analyzed with Principal Component Analysis (PCA) and regression analysis. Based on PCA results, the microstructure of rejuvenated binders has shown a good correlation with stiffness after combining various principal components. According to regression analysis, the distance between adjacent fibrils exhibited a significant correlation with Jnr3.2 and the complex modulus index. Overall, the results of this study strengthen the hypothesis that the ESEM microstructure is intimately correlated with chemical composition and rheological properties, rather than with irrelevant surface phenomena.Bitumen, polymer modified bitumen, rejuvenator, microstructure, rheology, environmental scanning electron microscopy.
Highlights
Asphalt binder is the main construction material for flexible pavements, and the worldwide production of asphalt materials is estimated to be more than a billion tons in 2019 [1,2]
The viscoelastic properties of the original, aged and rejuvenated binders were characterized with master curves of complex modulus and phase angle
The short-term aging mainly led to a modulus increase of polymer modified bitumen (PMB) at the high frequency range
Summary
Asphalt binder is the main construction material for flexible pavements, and the worldwide production of asphalt materials is estimated to be more than a billion tons in 2019 [1,2]. The physical and rheological properties of bitumen [5,6]. In the recycling of RAP, the addition of the rejuvenator is an important way to recover the physical and rheological properties of aged binders [7,8,9,10,11]. There are plenty of studies about the effect of rejuvenators on binder rheology. Recent investigations have shown a close relationship of microstructure with chemical composition and rheological properties of bitumen [19,20,21,22,23], assisting on understanding the rejuvenation mechanism. The rejuvenator's effect on the microstructure of aged bitumen is not well understood yet
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