Quantitative characterize binder blending and diffusion in recycled asphalt mixture: An environmental-friendly solution using wooden cube and 3D fluorescence image technology

Abstract

Due to the undetermined extent of blending phenomena between virgin and reclaimed asphalt, the use of reclaimed asphalt pavement (RAP) is limited. Currently, there is no universally accepted method and uniform terms for the quantification of blending phenomena. To this end, this paper proposed a new method based on 3D fluorescence image technology (3D-FIT) by using laser scanning confocal microscope. Natural asphalt and wooden cube were used to prepare RAP under laboratory aging for specific needs, styrene-butadiene-styrene (SBS) as fluorescent particles from SBS modified asphalt were employed to trace and quantify the blending phenomena. Subsequently, the steps of standardized pretreatment on wooden cube were developed, such as correction of asphalt content, autofluorescence elimination, attenuation correction etc. Under this new method, two suggested parameters including degree of blending, homogenization coefficient were proposed, both of which depends on the fluorescence intensity decay function, homogenization coefficient was defined to describe the homogenization of virgin and reclaimed asphalt. Moreover, the concepts on degree of blending and degree of RAP binder mobilization were distinguished. Compared with existing methods, the combination of fluorescent particles and laser scanning confocal microscope (LSCM) can perform three-dimensional observation and quantitative characterization for blending phenomena. It also provides a new attempt to analyze and evaluate blending and diffusion on the interface between asphalt and aggregate.