Possibilities of structure stabilisation in saliniferous formations using salt grit as a filling material

The final disposal of high-active wastes in deep geological formations is an issue of great national and international import. On account of its good thermal conductivity and creep capability much research is currently focussed on sand as a host rock material. After the emplacement of wastes in abandoned mining cavities these must be sealed up to prevent fluids from coming into contact with the wastes. This must be done using materials that are either native or similar to the materials of the host formation. A particularly suitable material in the case of saliniferous formations is salt grit. Up to this point investigations have primarily been focused on preparing a suitable salt grit material and the rheological properties of the binding agent. This article presents and interprets the results of preliminary experiments on the miscibility of salt grit and binding agent suspensions. The MgO and CaSO4-based binding agent systems analysed proved to be suitable. Among the MgO binding agents a composition of 3:1:8 was found to be more suitable than one of 5:1:8 on account of its lower initial viscosity. This reduces the amount of mixing required for wetting the material across all grain sizes, improving the chances of success. In the case of the two semihydrates of CaSO4 both the α and the β semihydrate proved suitable. This is due to a low fluid content which still also allows for a sufficiently low viscosity of the binding agent suspensions.