Laboratory Assessment of Recycled Asphalt Pavement as Roadway Embankment Material

Rehabilitation or reconstruction of roadways produces a large amount of recycled asphalt pavement (RAP). Typically, RAP is often reused as a part of hot mix asphalt. However, the in situ utilization of RAP offers advantages such as reduction of construction cost and expedition of construction process. On the other hand, including considerable percentages of RAP as a fill material in the embankment of pavement structures may increase the risk of settlement. In this study the behavior of RAP samples from five sources in Illinois, two conventional soils, and a lab-produced mixture of soil and RAP is investigated. Gradations, moisture–density relationships, dynamic triaxial, direct shear and one-dimensional consolidation tests at various conditions were performed. Results show that an increase in the temperature of RAP during compaction significantly increased the maximum dry density (MDD). Also, the mixed sample of soil and RAP results in the highest standard Proctor MDD. Increase in temperature significantly increased the compression of RAP. Achieving good settlement performance for RAP is feasible if the RAP samples are screened to pass 1.5-in. sieve and if the compaction of the RAP samples reaches 100% of standard MDD. Based on the dynamic triaxial testing, deformation of RAP does not stabilize as soils do. To mitigate this issue, it is recommended not to use RAP within the influence zone of traffic load, specifically the top 5 ft of an embankment in a rigid pavement structure and within the top 8 ft of an embankment in a flexible pavement structure.