The feasibility of using a solidified product of steel process residue in construction of a barrier system was investigated in the laboratory and in-situ. A solidified product of the dewatered sludge residue, filter cake, which exhibited high strength and low hydraulic conductivity was considered as a barrier cap for an existing lagoon. Variations in the placement and curing methods in the field, along with additive composition of the base mixture, influenced the strength development, hydraulic conductivity and durability of the resulting material. Strength of the material did not correlate well with hydraulic conductivity. However, high material strength appeared to increase resistance to freeze-thaw effects, thus demonstrating resistance to deterioration of the desired low permeability. Compositional variations such as proportion of surface reactive agents, water to cement ratio and the proportion of cement influenced strength as well as the measured hydraulic conductivity in the laboratory. Finally, a comparative analysis of fraction of three heavy metals removed by water permeation of three different composite samples demonstrated that chemical processes during the solidification may play an active role in the performance of the final product. Three slightly different composites of fairly high strength and low hydraulic conductivity showed selective release of cadmium from the solidified material.