Evaluation of Recycled Shingles as Structural Fill

The objective of this research was to evaluate the geotechnical properties of recycled asphalt shingles (RAS) as structural fill material in highway embankments or backfill material behind retaining structures and to provide relevant design guidelines. The research addressed the following hypotheses: 1- RAS as a granular material has sufficient shear strength and drainage capacity to qualify as a structural fill. Since RAS contains asphalt cement and cellulose felt, the material may exhibit higher compressibility compared to traditional fill material. 2- Addition of less compressible materials to RAS or stabilization of RAS can reduce the compressibility and increase shear strength and drainage capacity of RAS. 3- Since RAS contains asphalt cement, temperature variation affects its engineering properties. 4- Since RAS contains asphalt cement, time-dependent shear or volumetric strain under sustained deviatoric stress may be significant. The main chapters (Chapter 2, 3, and 4) are written as individual self-contained technical articles. In Chapter 2 entitled “Recycled Asphalt Shingles Mixed with Granular Byproducts as Structural Fill”, physical and mechanical properties of RAS and RAS mixed with granular industrial byproducts including bottom ash (BA) and foundry slag (FS) are evaluated in a systematic manner. Results show that although pure RAS has suitable drainage capacity and shear strength as structural fill, compressibility of RAS is significant compared to natural soils. Systematic addition of BA and FS to RAS reduced the compressibility and increased shear strength and drainage capacity of RAS:BA and RAS:FS mixtures. Design graphs were developed to estimate geotechnical properties of RAS:BA and RAS:FS mixtures for a given RAS content and stress level. In Chapter 3 entitled “Evaluation of Fly Ash Stabilization of Recycled Asphalt Shingles for Use in Structural Fills”, self-cementing (Class C) fly ash was used to stabilize RAS. Results show that stabilization remarkably reduces compressibility and increases the shear strength of RAS. However, stabilization also reduces the drainage capacity of RAS to that of silty sand or silty clay soil. Chapter 4 entitled “Effect of Temperature on Geotechnical Properties of Recycled Asphalt Shingles Mixtures” evaluates the effect of temperature change on geotechnical properties of compacted RAS:BA mixture and stabilized RAS. The development of a thermomechanical system and test procedures at elevated temperature are described. Systematic mechanical tests at elevated temperatures were conducted on RAS:BA and stabilized RAS specimens. The results show that when temperature increases, the shear strength decreases but compressibility and hydraulic conductivity increases. The shear strength and hydraulic conductivity of RAS containing embankments or stabilized RAS are sufficient to provide stability and drainage capacity of road embankments at different climates in North America. However; to minimize long-term settlement, compaction and construction of RAS embankments are recommended in warm season of the year. Chapter 5 contains summary and conclusion of the research conducted on RAS. Appendix I includes a paper that investigates geotechnical properties of RAS mixed with foundry slag in greater detail as well as the practical implications for estimation of settlement of typical highway embankment constructed with RAS:FS mixture.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 200p

Subject/Index Terms

Filing Info

  • Accession Number: 01531729
  • Record Type: Publication
  • Files: TRIS, ATRI, USDOT
  • Created Date: Jul 17 2014 12:04PM