Urban demand has increased the need to redevelop contaminated land. New legislation for land management has actively discouraged previously acceptable dig and dump practices. This has encouraged in-situ remediation approaches, for which stabilisation / solidification (S/S) is particularly suitable for treating metal contamination. However, concerns over long-term effectiveness and durability of S/S needs to addressed, because contamination is contained but not removed. This requires effective chemical assessments to inform design. This study aims to design a suitable method for assessing S/S effectiveness, using a holistic risk based approach, for use during performance based S/S design. The processes that induce containment were evaluated, by assessing the solubility controlling mechanisms, and undertaking geochemical speciation modelling, to determine solubility controlling minerals. These findings can be used at the design stage to engineer S/S application to particular sites, and ensure long-term performance with minimal risk. Evaluations for structural master species (Al, Si, and Ca) and contaminants (Zn\(^2\)\(^+\), Cr\(^3\)\(^+\)) in cement stabilised contaminated kaolin were undertaken. The influences of common soil components (Humic acid and sodium sulphate), and increasing hydration durations were also assessed, to inform containment effectiveness and chemical durability. Findings showed that the assessment method was suitable for chemical characterisation of stabilised matrices, as a tool for informing design and application.