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 percentages between 6 and 15%, and examined for use as a constituent in a landfill liner in terms of compaction, unconfined compressive strength, stress-strain behavior, permeability to water and paraffin, leachability, 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 as low a 40% of the strength of the clay alone. In stress-strain behavior the clay-tin mixtures produced a prolonged strain range at failure of roughly double that observed for the clay alone. The permeability to paraffin was reduced by more than 50 times compared to that of water. The leachability results showed different leached levels of copper and nickel from the NRA and TCLP leaching tests which will need to be assessed in relation to appropriate standards. Paraffin caused considerable swelling of the clay-tire mixtures compared to the clay alone and caused the development of swelling pressures of up to 600 kPa. Combinations of the various test results will need to be assessed in relation to the design requirement of the specific landfill liner being designed. (C) 1998 Elsevier Science Ltd. All rights reserved.