Use of Raw Chat in Hot-Mix Asphalt Surface: Environmental and Engineering Characterization

Over 35 million cubic meters of mine chat, a waste material from abandoned lead and zinc mining operations, are presently stockpiled in large piles on the surface of the Tar Creek Superfund Site. Currently, the Oklahoma Department of Transportation (ODOT) uses a rather small percentage (about 20%) of washed (not raw) chat in surface and base mixes. There is a pressing need to significantly increase the use of raw chat in hot mix asphalt (HMA) by ODOT and other DOTs in the region. No systematic bench-scale tests have been performed previously for characterization and use of raw chat in HMA in an environmentally responsible manner. This study reveals that raw chat is an excellent aggregate in HMA. As much as 80% raw chat can be used in a S5-type Superpave surface mix. Chat is an excellent source of enhancing voids in minerals aggregates (VMA) in HMA. Even a relatively small percentage (40%) of raw chat produces high VMA (15% or more), and it increases with an increase in chat percent. Relatively high optimum binder contents are required in chat-asphalt. A systematic analysis of different volumetric parameters is presented. Chat-asphalt mixes also did well in performance tests, namely moisture susceptibility, APA rut, and permeability. In addition, a suite of environmental tests was performed to examine the leaching potential of heavy metals (lead, zinc, and cadmium) in chat due to dry and wet rut tests, and simulated milling. Environmental tests indicate that chat-asphalt can be used safely as a roadway surface.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 15p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01046294
  • Record Type: Publication
  • Report/Paper Numbers: 07-3193
  • Files: PRP, TRIS, TRB
  • Created Date: Feb 8 2007 7:54PM