1. Introduction and Objective

Cementitious materials are being widely used as solidification/stabilisation and barrier materials for a variety of chemical and radioactive wastes, due to their favourable retention properties for metals and other inorganic contaminants. These result from mineral phases in hydrated cement that (i) possess a high density of sites for the fixation of contaminants through a variety of sorption and incorporation reactions and that (ii) buffer pH in the range 10–13, depending on composition, which tends to limit the solubility of many metal ions. The present book represents a state-of-the-art review and evaluation of the type and magnitude of the various sorption and incorporation processes in hydrated cement systems for twenty-five elements. It is aimed at describing the interaction of dissolved constituents with hydrated cementitious materials (i.e. already set or hardened). While the immobilisation of contaminants by mixing with dry cement clinker before hydration is not explicitly addressed, many underlying processes will be similar. On the basis of a consistent review and re-evaluation of the literature data, we established a quantitative database on the solid/liquid distribution behaviour (“sorption database”) for radionuclides and other elements in hydrated cement systems. This database is closely tied to the safety analysis of the near-surface disposal of radioactive waste in Belgium, which is reflected in the focus on radioelements. However, the book addresses also a number of stable elements and heavy metals, which makes it relevant for the interaction of conventional contaminants with cement-based barriers.