Influence of Residue Fillers and Fine Particles on Extracted and Recovered Bitumen Binders

Abstract

Accurate extraction and recovery of bitumen from reclaimed asphalt pavement (RAP) is essential for evaluating binder aging and ensuring reliable mix design. Current standards, such as EN 12697-1, prescribe sieving and centrifugation to remove aggregates and fillers, yet it remains unclear to what extent residual particles persist and how strongly they affect binder properties. In this study, unmodified and polymer-modified binders were recovered from mastics, laboratory-aged mixtures, and RAP, with and without additional filtration. Rheological testing and darkfield microscopy were used to assess the influence of residual particles. Results showed that the EN 12697-1 procedure did not fully remove fillers and aggregate fines, which significantly increased binder stiffness. A comparison of 8 mm and 4 mm mixtures further indicated that aggregate fines contributed more strongly than mineral filler. Fine filtration (≤2–1 μm) reduced residues and lowered stiffness indices close to those of the original binder. These findings highlight the limitations of current standards and the need to refine EN 12697-1 procedures for accurate binder characterization.