The mechanical behaviour of salt concrete with special consideration of its use in dam construction in a repository for nuclear waste in a mine

In consideration of its use in an ultimate repository for nuclear waste in a mine, the mechanical properties of salt concrete are of particular importance, but so are its gas permeability and structure after stress. The investigations were carried out not only on salt concrete samples which hydratised under normal conditions, but also on sample blocks which had been subjected to deformation prestressing after hydratisation, in order to create pronounced flow structures. This was intended as a simulation of in-situ deformation resulting from extreme strain. The cement matrix and the rock salt additive show marked creep and indicate similarities with rock salt. The binding agent/additive compound is maintained intact, and the two components remain firmly bonded together even after major deformation, cracking only when rupture mechanics set in. Higher strain leading to slip and deformation of the additive shows that the cement matrix follows the distortion of the salt grains. The monoaxial compression strengths between rock salt and salt concrete are very similar, although salt concrete achieves higher values. The permeability of salt concrete is lower but comes close to that of rock salt when compacted. The results show that salt concrete appears to be a suitable construction material for the buttress of a dam structure in a nuclear waste repository. (orig./MM)