Cement formulations that have been developed in the United Kingdom (UK) for treating radioactive wastes are described. Primarily, blends of ordinary Portland cement with ground granulated blast furnace slag or pulverized fuel ash have been shown to possess adequate processing performance and product properties when used to encapsulate a wide range of radioactive wastes. The versatility of these formulations is demonstrated by reference to the key process and product properties necessary to meet identified criteria for disposal of radioactive wastes. In particular, the development of the strength, structure, and the solid and liquid phases with time is discussed. An illustration is given of the selection and development of a cementation process for immobilization of Winfrith reactor waste sludges.