Investigating the effect of using unclassified fractionated reclaimed asphalt pavement materials on the properties of hot mix asphalt

Abstract

Reclaimed Asphalt Pavement (RAP) incorporation is bounded by many specifications that limit its increased utilization. One of them, which many road agencies adopt, is the allowance of RAP from known single origin “classified RAP” only to be utilized in new mixtures. A lot of asphalt plants cannot afford space for multiple small RAP stockpiles in their yards and are forced to accumulate “unclassified” RAP materials collected from several projects into a single zone, hence, the “classified RAP” specification restricts the benefits of their utilization. In this context, this study aimed to investigate the pros and cons of using unclassified fractionated RAP with 15%, 25% and 45% percentages in Superpave asphalt mixtures. Complex modulus testing was performed on three replicates of each asphalt concrete (AC) mixture to evaluate the dynamic modulus |E*| and phase angle Φ properties over a range of temperatures and loading frequencies. As well, Flow number (FN) test was conducted to assess the rutting potential of the mixtures. The results showed that no significant difference existed between |E*| and Φ values of conventional hot asphalt mixture (HMA) and other RAP mixtures over the full analyzed range of frequency which indicates that the utilization of low, medium or high percentages of unclassified RAP materials may be indeed appropriate. Finally, the results of the flow number test and the simple performance indicator were compared and used to rank the rutting resistance of the assessed mixtures.