Abstract: The concentrated solution sludge (CSS) produced by submersion combustion process has special characteristics, such as high water content, low organic matter and heavy metals content and extremely high salinity. In this study, sulfoaluminate cement (SAC) was used as the main curing agent, and two kinds of waste incineration fly ash and bottom ash were added as auxiliary curing agents to quantificationally investigate the influence of different curing agents on the solidification effectiveness of CSS, and various solidified CSS samples with a variety of curing agent combinations were prepared for a series of unconfined compressive strength tests, water stability tests and microscopic observation tests. The results show that the strength of CSS solidified with 10% SAC can meet the strength requirement (50 kPa) of landfill under the condition of 7 d curing age; the 28 d strength of the cement solidified samples meet the requirement of water stability as the SAC content exceeds 50%. The optimal dosages of fly ash and bottom ash of 28 d solidified samples are 5% (SAC content <40%) and 10% (SAC content ≥40%). Bottom ash is more effective than fly ash for improving water stability of solidified samples. The SEM and XRD results show that the formation of interlocked structure composed of hydration product of cement and ettringite crystal generated from the interaction between SAC and fly ash or bottom ash, is the major factor improving the water stability of solidified samples with a certain dosage of fly ash or bottom ash.

Key words: concentrated solution sludge, extremely high salinity, solidification/stabilization, waste incineration by-products, water stability