Identification on blending zone and qualitative analysis of blending degree in Recycled Asphalt based on ESEM-EDX analysis

Abstract

Recycled Asphalt (RA) offers economic and environmental benefits in pavement construction in Netherlands, but also faces a high potential for premature cracking, especially when it is used in porous asphalt. The RA production process, due to the incorporation of Reclaimed Asphalt Pavement (RAP), exhibits a higher tendency to form heterogeneous blending zones, which are often regarded as weak areas susceptible to cracking. However, preliminary research was not systematically describing blending zones at the microscale. To develop a reliable method for characterizing the blending degree in RA, this research employed the ESEM-EDX microscopic testing method to analyze its internal structure, with a particular focus on the distribution of different components. Based on the varying Ti tracer content in fresh and aged mastic, an identification method was developed and validated for its feasibility in distinguishing four RA components: aggregate, fresh mastic, blended mastic, and aged mastic. By appling this identification method, qualitative analysis of the blending degree revealed that fresh aggregates achieve a more thorough blending state than RAP aggregates. This research advances the understanding of RA's internal structure and blending behavior, providing another characterization choice for quantitative analysis of blending degrees in RA.