Laboratory and field evaluation of plant produced asphalt mixtures containing RAP in hot climate: A case study from Phoenix, Arizona

The use of Reclaimed Asphalt Pavement (RAP) in asphalt mixtures has been gaining wide attention over the past four decades. However, the use of RAP in asphalt mixtures in harsh hot climate areas such as Phoenix, Arizona has been slowly and cautiously addressed due to the aged characteristics of the RAP and lack of performance data. This study aimed at evaluating such RAP mixtures in the laboratory using field produced Hot Mix Asphalt Mixtures (HMA). Based on detailed mix design efforts, three test sections were constructed in Phoenix: the first being a control (0% RAP), the second and the third sections with 15% and 25% RAP contents, respectively. During construction, loose HMA mixtures were sampled for advanced laboratory material characterization tests. The testing program included stiffness, permanent deformation, cracking potential, and moisture damage resistance. In addition, asphalt binder testing was performed on extracted and recovered binders. The laboratory results on the RAP mixtures indicated that adding 15% and 25% RAP to the mix did not have significant effect on increasing stiffness, but improved the rutting resistance, had comparable cracking performance, and had acceptable moisture damage resistance. The binder testing that was performed on the extracted and recovered binders yielded results that supported the asphalt mixtures’ testing analysis. The field performance monitoring of the three test sections showed similar performance. Based on the results of this study, it was recommended to incorporate RAP as a sustainable paving activity up to the percentages used in this study.