Assessment of the impacts of sample preparation on the use of EDS for analysing recycled asphalt blending

Abstract

Several past studies have demonstrated merit to using tracer‐based energy dispersive X‐ray spectroscopy (EDS) analysis to investigate blending between virgin and recycled materials in asphalt mixtures. However, these past studies have focused on proof of concept and did not establish robust fabrication and microscopy procedures. This study rigorously evaluates the ability to form a stable blend between the tracer and virgin asphalt binder, and the potential for tracer smearing during the preparation of EDS specimens. The results demonstrate that a high shear mixer can be used to prepare homogeneous, stable blends of a titanium dioxide tracer and virgin binder. A critical evaluation of an asphalt mixture specimen prepared to contain specific areas with and without the tracer demonstrates no evidence of tracer smearing due to sample preparation. The results demonstrate that tracer‐based EDS analysis of asphalt mixtures can measure local recycled material availability.

Application of Sieve Analysis to Estimate Recycled Binder Availability

“…The addition of the titanium dioxide tracer to the virgin binder to distinguish it from the RAP binder turns the virgin binder brown, as noted in Pape and Castorena (14,15). Consequently, regions in asphalt mixtures containing only virgin binder or a combination of recycled and virgin binders appear brown.…”

“…The tracer used in this work was a titanium dioxide microparticle powder, with an average size of 0.2 microns. Specimens for EDS analysis were prepared using tracer-modified virgin binder with a tracer dosage of 10%, as recommended in Pape and Castorena ( 14 ). Details on the recycled binder contents and virgin binders, including input parameters needed for quantitative EDS analysis, are summarized in Table 2; explanation of these input parameters is provided in the following section.…”

“…The gyratory specimens were reduced to 25 × 25 × 12 mm prisms, following the same procedure as Castorena et al ( 11 ). The specimens were polished using the procedure outlined in Pape and Castorena ( 14 ).…”

“…However, the limitations of EDS detectors in the 1980s made further investigation impractical. Rinaldini et al revived the idea (9), inspiring other researchers to build on their proof-of-concept study (10)(11)(12)(13)(14)(15). Through these additional research initiatives, the concepts underpinning tracer-based EDS analysis and questions surrounding the use of a tracer and the impact of specimen fabrication and preparation on inferences of recycled binder availability have been thoroughly explored and addressed (14).…”

“…Rinaldini et al revived the idea (9), inspiring other researchers to build on their proof-of-concept study (10)(11)(12)(13)(14)(15). Through these additional research initiatives, the concepts underpinning tracer-based EDS analysis and questions surrounding the use of a tracer and the impact of specimen fabrication and preparation on inferences of recycled binder availability have been thoroughly explored and addressed (14). Earlier studies focused on qualitative observations of the uniformity of tracer dispersion within the binder matrix of mixtures (9,10).…”