Chemical leaching assessment and durability evaluation of cement stabilized zinc contaminated kaolin clay

Sustainable redevelopment to meet increasing urban expansion has mandated the increased redevelopment of contaminated land. Current national / international environmental regulations, and increased disposal costs for landfilling, has necessitated a need for sustainable and cost efficient in situ remediation alternatives. Stabilization / Solidification (S/S) techniques offer a viable solution for the amelioration of unacceptable environmental risk, particularly effective in heavy metal remediation. However, uncertainties over long term effectiveness and durability, and previously low landfill disposal costs had limited its utilization. Effective characterization of the stabilized material and evaluation of its leaching and containment properties are required, to ensure long term effectiveness and improve design confidence. Zinc contaminated kaolin clay, stabilized with CEM II Portland Limestone cement, was tested using a suite of leaching tests designed for monolith specimens. Evaluations of leaching for zinc and selected master species (Al, Si and Ca) were undertaken, at different intervals of hydration (28, 150 and 300days). Results show that zinc is successfully contained and partitioned within the cement stabilized kaolin clay, but does not exhibit amphoteric leaching. Increased hydration time increases the stabilized materials chemical durability regardless of kaolin degradation, but does not modify pH dependent leaching trends.