Effect of Curing Temperature on the Geotechnical Behavior of Solidified Sludge in Landfill Temporary Cover Applications

Elevated temperature in municipal solid waste will affect the performance of earthen materials in a landfill cover liner system. Soda residue (SR), ground granulated blast furnace slag, and quicklime were utilized as solidifiers in sewage sludge, and the curing temperature effect on geotechnical behavior of solidified sludge in landfill temporary cove applications was investigated. The unconfined compressive strength, yield stress, coefficient of compressibility, hydraulic conductivity, and microstructural and mineralogical characteristics of solidified sludge at various curing temperatures were measured. Hydration products including ettringite crystals and calcium-silicate-hydrates (C-S-H) were observed in the samples. An increase in temperature from 12 to 40°C improved the solidified sludge strength, but a further increase to 60°C decreased the strength. The lowest coefficient of compressibility and the lowest hydraulic conductivity were observed at 40°C. The pore volume or pore size of the solidified sludge decreased with the increase in temperature. However, the geotechnical performance was improved due to the increase in C-S-H and decrease in ettringite in 40°C sample. 50% SR content was optimum for solidified sludge temporary cover due to its relatively high strength, high yield stress, low compressibility, moderate hydraulic conductivity, and good pollution stabilization capability at different curing temperatures.