Current Status of Reclaimed Asphalt PavementApplication in the United States

The use of reclaimed asphalt pavement (RAP) in the United States has continued to grow since it became more commonplace in asphalt mixtures in the 1980s. While originally, states highway agencies were concerned about mix design methodology and long-term performance, recent research has enhanced the state of the knowledge related to both of these topics. Best practices related to RAP sampling, testing, and material characterization have been developed to aid both contractors and departments of transportation in mix design and quality control. Additionally, recent research has suggested binder bumping is not necessary when using less than 25% RAP in a mix. Projects such as National Cooperative Highway Research Program Project 9-46 have also shown that volumetrics may not be sufficient for assessing mixture performance. Low-temperature testing, rutting susceptibility assessment, cracking resistance, moisture susceptibility, and mixture stiffness should be assessed based on regional requirements. The asphalt industry needs to continue to assess which performance tests will provide the best correlation to field performance.