Performance of cementitious systems in the repository

The behaviour and performance of cement barriers in the repository have been modeled. Since the models employ thermodynamic calculations, an important task is the development of a validated database. This must include phases and aqueous species appropriate to cement and modified cements, containing fly ash and slag. Closed system mineralogy and chemistry are explored as a function of cure duration and thermal excursions. Work has only just begun on open system behaviour: some aspects of reactions with chloride, sulfate and carbonate are described. Future progress depends on database extensions, validation experiments and the coupling of equilibrium and kinetic aspects of reaction