In a laboratory study, 15% (w/w) of ordinary portland cement (OPC), black portland cement (BPC) and puculanic cement (PC) combined with various cement additives were used for solidification/stabilization (S/S) of Cd, Pb, Zn, Cu, Ni and As contaminated soils from the former industrial site. Soil formed solid monoliths with all cements and cement additives. S/S effectiveness was assessed by measuring the mechanical strength of the monoliths, concentrations of metals in deionised water and TCLP (Toxicity Characteristic Leaching Procedure) soil extracts, and mass transfer of metals. Concentrations of Cd, Pb, Zn and Ni in water extracts from S/S soils generally decreased, while concentrations of As and Cu increased. Concentrations of Cd, Pb, Zn, Cu and Ni in the TCLP extracts from S/S mixes were lower than from original soil, while the extractability of As from S/S mixes increased. Overall, the concentration of metals in TCLP solution, obtained after extraction of the S/S mixes, was below the regulatory limits. S/S greatly reduced the mass transfer of Cd (up to 21.5-times), Pb (up to 114-times) and Zn (up to 999-times). Mass transfer of Ni was generally also reduced, while that of Cu and As increased in some S/S mixes. In general, monoliths made with OPC present higher cumulative mass of PTMs leached than those with BPC and PC.

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