NATURAL CLAY SHREDDED TIRE MIXTURES AS LANDFILL BARRIER MATERIALS

A natural overconsolidated fissured clay, Keuper Marl, was mixed with shredded tire, 1-4 and 4-8 mm angular size particles, in weight percen tages between 6 and 15%, and examined for use as a constituent in a la ndfill liner in terms of compaction, unconfined compressive strength, stress-strain behavior, permeability to water and paraffin, leachabili ty, free swell behavior and swelling pressure. The results showed that the compacted dry density reduced solely due to the lighter weight of the tire and the unconfined compressive strength of the mixture was a s low a 40% of the strength of the clay alone. In stress-strain behavi or the clay-tin mixtures produced a prolonged strain range at failure of roughly double that observed for the clay alone. The permeability t o paraffin was reduced by more than 50 times compared to that of water . The leachability results showed different leached levels of copper a nd nickel from the NRA and TCLP leaching tests which will need to be a ssessed in relation to appropriate standards. Paraffin caused consider able swelling of the clay-tire mixtures compared to the clay alone and caused the development of swelling pressures of up to 600 kPa. Combin ations of the various test results will need to be assessed in relatio n to the design requirement of the specific landfill liner being desig ned. (C) 1998 Elsevier Science Ltd. All rights reserved.