Integrated performance evaluation of asphalt mixtures with very high reclaimed asphalt pavement (RAP) content

Abstract

• Asphalt mixtures with very high RAP content (>50 %) can outperform conventional mixtures with regard to different performance aspects. • Conventional volumetric-based mix design methods are not sufficient for asphalt mixtures containing very high RAP. • Restoration of gradation based upon Bailey method was found effective regarding performance. • An integrated performance-based index was introduced to rank asphalt mixtures with high RAP content. Conventional mix design methods are incapable of making the most of RAP, especially in very high content (>50 %). RAP is not the kind of waste to just get rid of, but it has the potential to build better asphalt pavements. Therefore, the aim of this research is to modify practices and criteria within mix design and develop a ranking system in order to better fabricate and evaluate asphalt mixtures containing very high RAP, respectively. The specific challenges of this mixture type including gradation, production, compaction, volumetric properties and optimal asphalt content (AOC) were handled in this study. Also, a general performance index integrating essential performance aspects including rutting, cracking, aging and moisture sensitivity was developed. It had been found that rejuvenation and aging potential are important in mixtures with very high RAP content, so rejuvenation was made based upon previous studies and aging potential was included in the performance evaluation. Paying more attention to gradation within mix design was proved very important and Bailey method was found impactful on improving aggregate structure of mixtures with high RAP content. It was observed that the target air void of 3 % leads to better coating of virgin aggregates of this mixture type.