INFLUENCE OF VOID CHANGE, CRACKING, AND BITUMEN AGING ON DIFFUSIONAL LEACHING BEHAVIOR OF PAVEMENT MONOLITHS CONSTRUCTED WITH MSW COMBUSTION BOTTOM ASH

The evaluation of leaching behavior of monolithic forms containing waste materials requires the use of leaching tests that evaluate diffusional release mechanisms. This can be coupled to procedures that accelerate the aging of the monolith to better predict long-term leaching behavior. As part of a comprehensive demonstration project examining the use of municipal solid waste combustion bottom ash as an aggregate substitute in bituminous binder course, the diffusional leaching behavior of ash constituents was assessed as a function of pavement voids level (5, 7.5, 10%), bitumen aging (none, medium, high), and monolith cracking (none, medium, high). Effective diffusion coefficients were determined for some ash constituents that leach; values ranged from "10 to the -12 power" to "10 to the -16 power" sq m/sec. These values are typical for ion diffusion in polymer systems. Species with small ionic radii (e.g., Na, Cl) were more diffusive than those with large ionic radii (e.g., Si, Zn). Monolith tortuosity values were found to be influenced only by monolith cracking. Diffusing specie chemical retention values and effective diffusion coefficients were not influenced by voids, cracking, or aging. Bituminous pavement monoliths release ash constituents at very low fluxes. Modeled releases of chloride for 10% wetting ranged from 1.7 g Cl/sq m/1.5 years to 54.9 g Cl/sq m/100 years. These fluxes are considerably smaller than fluxes associated with road salting during a single snowfall. The tortuous, hydrophobic nature of the monolith system controls diffusion.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 42-48
  • Monograph Title: Environmental testing and evaluation of stabilized wastes, performance of stabilized materials, and new aggregate tests
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00713586
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Nov 22 1995 12:00AM