Use of sedondary construction material in landfill cover liners

The applicability of fly ash - sewage sludge and steel slag mixtures in landfill cover liners was investigated putting special emphasis on the hydraulic conductivity (HC) of the materials. The objective was to identify the factors significantly affecting the HC of the materials and to quantify their effects using multiple linear regression (MLR). It was discussed what impact low-HC liners might have on the landfill system and the environment. Although mainly affected by the COMPACTION ENERGY used, the HC of the fly ash - sewage sludge samples were also affected by DRYING and the factor interactions MATERIAL×ASH RATIO and ASH RATIO×COMPACTION ENERGY. The models derived using multiple linear regression could be used to predict an HC between 1.7×10-11 m s-1 and 9.5×10-10 m s-1, if a compaction energy of 2.4 J cm-3 was applied and no drying occurred. TIME between the addition of water and compaction mainly affected the HC of the steel slag samples. The HC of the steel slag mixtures was between 10-8 and 10-12 m s-1 if they were compacted immediately after water addition. The HC showed a decreasing trend during the measurement period of 53±1 days. It was suspected that cement reactions in the material influenced HC. Low-HC liners are a potential environmental hazard. Monitoring of landfill emissions is prescribed for about 30 years though contaminated landfill leachate is generated for at least one human generation. As the failing of the liner can go along with a sudden increase of leachate release from the landfill and thus with severe environmental pollution, the concept of applying low-HC liners needs to be reconsidered.<p>Godkänd; 2006; 20070109 (mlk)