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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Investigating the Statewide Variability and Long Term Strength Deformation Characteristics of RAP and RAP-Soil Mixtures

Reclaimed Asphalt Pavement (RAP) usage is limited because tests on RAP and RAP-soil blends indicate that creep may pose a concern and the statewide variability of RAP has not been addressed. RAP was blended with A-3 sands and the results showed that the addition of 20% A-3 improved the gradation, density, and bearing strength of RAP. Conventional highway materials testing was performed. The one-dimensional creep behavior of RAP and RAP-soil blends was evaluated. Axial strains were analyzed using Singh and Mitchell's approach. Using the resulting strain rate equations, settlements versus time predicted correctly characterized the material behavior. The soil in the RAP-soil blends effectively lowers the asphalt content. Blends containing less than 3.5% asphalt produced substantially lower strain and were not influenced by the applied stress level. The backfill settlements increased exponentially with increasing wall height. The exponential growth was faster at higher RAP contents. Most settlement was predicted to occur during construction. Horizontal and vertical creep and pullout characteristics of reinforcement embedded in 100% RAP, 50/50% RAP-sand blends and 100% A-3 were evaluated. The 100% RAP consistently produced the lowest pullout capacity of the steel reinforcing strips and the greatest reinforcing strip displacement of the three materials during pullout testing. The 50/50% blend yielded the greatest pullout capacity, however this blend yielded a greater strip creep displacement than the A-3. The 100% RAP yielded the largest vertical creep displacement followed by the 50/50% blend and A-3. For alternating RAP and sand layers, placing the sand as the top layer substantially reduced the amount of vertical creep. As a result of this work, it is recommended that RAP and RAP-sand blends not be used in mechanically stabilized earth (MSE) wall applications. The statewide variability testing program was performed on milled or crushed RAP. The asphalt content of RAP can vary from 3.5% to 11.0%. Typically milled RAP varies between 5.5% and 8.0% asphalt while crushed RAP varies from 4.5% to 7.0% asphalt due to blending. RAP's moisture density behavior is non-Proctor like. No RAP materials tested in this study met the minimum Florida Department of Transportation (FDOT) base course unsoaked Limerock Bearing Ratio (LBR) value of 43. RAP should not be used as a base or subbase course material under highway pavements. Asphalt content is correlated to the engineering behavior of RAP. For every 1% increase in asphalt content, there is a decrease of 3.8 lb/cu ft in compacted density and a decrease of 4.5 in the LBR value. RAP materials with high asphalt content should not be used in earthwork applications where bearing strength is required.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 412p

Subject/Index Terms

Filing Info

  • Accession Number: 01101653
  • Record Type: Publication
  • Report/Paper Numbers: FL/DOT/RMC/06650-7754
  • Contract Numbers: BDB09
  • Files: TRIS, STATEDOT
  • Created Date: Jun 13 2008 4:14PM