First Observation of Blending-Zone Morphology at Interface of Reclaimed Asphalt Binder and Virgin Bitumen

Abstract

One of the challenges in designing recycled asphalt mixtures with a high amount of reclaimed asphalt pavement (RAP) is estimating the blending degree between RAP binder and added virgin bitumen. The extent of blending is crucial because asphalt concrete response is influenced by the final binder properties. This paper focuses on the evaluation of interaction and extent of blending between RAP binder and virgin bitumen by studying the microstructures of the blending zone with atomic force microscopy (AFM). AFM is used to probe the change of microstructural properties from a RAP binder and virgin bitumen to the blending zone of these two. Averaged microstructural properties have been observed in thin-film blends of RAP binder and pure bitumen. The morphology of the blending zone (spatial extent of about 50 μm) exhibits domains of a wide range of microstructure sizes (160 nm to 2.07 μm) and can be considered to be a completely blended new material that has been observed directly for the first time. The fully blended binder properties are found to be between those of the two individual binders, as could be inferred from the averaged microstructural properties derived from AFM images of the blending zone. This finding is also consistent with the results of mechanical tests by dynamic shear rheometer on the same materials. Finally, a design formula is proposed that relates the spatial dimensions of the blending zone to temperature and mixing time, which will eventually allow the results of this study to be extended from small-length scales up to the engineering level.

Impact of maltene and asphaltene fraction on mechanical behavior and microstructure of bitumen

“…4b) Four micro-phases are evident from the bitumen microstructure. A typical domain phase with a wrinkling along the long axis, most often termed as bee structure or catana phase, is observed to be dispersed over a continuous matrix phase (perpetua phase) [44][45][46][47][48]. The domain phase with wrinkling and the matrix phase are often considered to be the characteristic features of the bitumen microstructure [44,[47][48][49][50].…”

Soft bitumen asphalt produced using RAP

“…More detailed aspects of old and new binder mixing, especially in the complex asphalt concrete mixture matrix were not studied. Interesting recent research includes studies on clustering effects [27] and atomic force microscopy of the old and new binder interface [28], among others.…”

Metoda Oceny Mieszalności Lepiszczy W Mieszankach Mineralno-Asfaltowych Z Destruktem

“…Atomic Force Microscope) służąca m.in. do oceny rozmieszczenia cząstek polimeru w mieszaninie asfaltów [8].…”