Durability Issues for Concrete in a Deep Geologic Repository

Abstract

Concrete and cement-based materials are being considered in the design for sealing components in emplacement rooms, access tunnels, shafts and ramps and boreholes for deep geologic repositories. Cement-based materials are being considered as a grout material to isolate hydraulically active fractures and to fill interfaces between concrete and rock. Concrete may be used as a working surface floor in emplacement rooms and in access tunnels and as large structural seal components in composite seal systems. In some applications concrete may be used as a tunnel support in the form of shotcrete or rock bolt grout. Because of the potential for their wide use in various applications and locations, concrete and cement-based materials in a repository would experience different conditions at different times. These conditions would be related to the degree of saturation of the surrounding materials, the groundwater composition and movement, the rock type and character, and the extent of its exposure to either air or heat from containers. This paper reviews the potential mechanisms that could affect durability of concretes and grouts used in a repository.