Environmental suitability of recycled concrete aggregate in highways.

Details

• Creators:
  Aydilek, Ahmet H.
• Corporate Creators:
  University of Maryland (College Park, Md.)
• Subject/TRT Terms:
  • Pavement design
  • Aggregate gradation
  • Concrete aggregates
  • Recycled materials
  • Laboratory tests
  • Modulus of resilience
  • Deformation
  • Durability
  • California bearing ratio
  • Freeze thaw tests
  More +
• Publication/ Report Number:
  MD-15-SP109B4G-2
• Resource Type:
  Tech Report
• Geographical Coverage:
  Maryland
• Corporate Publisher:
  Maryland. State Highway Administration. Office of Policy & Research
• Abstract:
  The use of recycled concrete aggregate materials in highway constructions as compared to the use of virgin ; materials reduces virgin natural resource demands on the environment. In order to evaluate their potential use of ; recycle materials in highway construction, two different recycled concrete aggregate (RCA) materials and two ; conventional graded aggregate base (GAB) materials and the mixtures of RCA-GAB materials were tested in the ; laboratory for their strength (California Bearing Ratio), resilient modulus, permanent deformation, and durability. In ; addition, laboratory water leach tests (WLTs), and pH-dependent leaching tests were conducted to determine the ; environmental suitability of RCA materials. The leaching behavior of Ca, Cr, Cu, Fe, and Zn from RCAs and the ; effects of pH, curing time, freeze/thaw cycles, liquid-to-solid ratio, and particle size on leaching of these metals were ; investigated. The summary resilient moduli (SMR) of RCAs were 2.6 and 2 times higher than that of the natural ; GAB material and their stiffness increased when subjected to freezing and thawing cycles. Consistent trend could ; not be observed with CBR and SMR values and percent RCA addition. Overall, GAB yielded lower permanent ; deformations compared to the RCA materials. In pH-dependent leaching tests, Ca showed cationic leaching patterns, ; while Cr, Cu, Zn, and Fe showed amphoteric leaching patterns. Leaching tests results indicated that leached Zn ; concentrations were below the detection limits at pH>5. Increasing curing time caused rehydration of cement ; particles and generally yielded a decrease in pH and leached concentrations of metals. Freezing and thawing of ; RCA also led to self-cementing and decreased pH, Ca concentrations while no consistent trends were found between ; the leaching of Cr, Cu, and Fe concentration and freeze-thaw cycles. Increasing the liquid-to-solid ratio decreased ; leaching of elements significantly due to the dilution of leached elements in the aqueous solutions.
  More +
• Format:
  PDF
• Funding:
  SP109B4G
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/28447/dot_28447_DS1.pdf
• File Type:
  [PDF - 331.95 KB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:07cd91baab80e5b17fc8c1e3a8a633a8741d8c40af0fee095f9c8e8b5500c647