Stabilization of sulfide-rich sediments with industrial side streams

The dredged spoils in the coastal areas of Finland are very likely potential
acid sulfate soils that, when spread on land, begin to oxidize and form sulfuric
acid. The drop in pH dissolves harmful elements from the clay that are
transferred to the environment with the runoff water.
Chemical analyses were performed to determine the pre-incubation
characteristics of the fresh sample and the sample after 19 weeks of
incubation. The total concentration of the elements in the spoil was analyzed
after digestion in aqua regia. The leaching of metals and metalloids was
determined by using the two-stage shaking test method.
Seven recipes with industrial side stream (ash, blast furnace slag and lime
residues) additions were developed, with an emphasis on reducing the amount
of cement needed for clay stabilization. Both laboratory and field tests were
performed. The unconfined compression strength (UCS) was determined after
7, 28 and 91 days. The leaching of elements from the stabilized samples was
determined.
The measured strength development and successful immobilization of
harmful elements suggest that sulfate-rich sediments can be used as building
ground materials. Industrial side streams can substitute part of the cement
traditionally used for stabilization. Accordingly, a significant reduction in
carbon footprint, calculated as CO2 emissions, can be achieved.