Characteristics of products made in the process solidification and stabilization of fly ash from combustion of sewage sludge

Piotr Wichowski, Marek Kalenik, Gabriela Rutkowska, Maciej Malarski, Justyna Czajkowska, Wojciech Franus

The article presents an analysis of the results of research on the composition of fly ash from the thermal processing of sewage sludge [SSA] collected from three incineration plants located in Warsaw, Cracow and Łódź. It determines the leaching values of selected heavy metals from the tested fly ash and ordinary class concrete C20/25 with partial replacement – up to 20% of cement with fly ash. The laboratory tests performed showed that they have a comparable granulometric composition. In contrast, the physico-chemical properties of the tested fly ashes differ from ashes from coal combustion traditionally used in concrete technology. SSA is characterized by an average lower content of silicon, iron, and aluminium oxides with a much higher content of phosphorus oxides. Leaching tests indicate low mobility of heavy metals, meeting Polish regulations regarding the possibility of using SSA in construction for specific applications. At the same time, they do not pose a significant threat to human health or the environment. Construction waste containing SSA may be disposed of in inert waste landfills.

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