Assessment of the properties of polycrystalline rock salt synthesized under nominally dry and wet conditions

Polycrystalline rock salt’s compression is a function of applied stresses, exposure duration to the applied stresses, ambient temperature, and water content. Rock salt’s compressional behavior under different conditions and its effects on the specimens’ mechanical properties have been investigated in the literature. However, the one-dimensional (1D) compression behavior of polycrystalline rock salt at various water contents and how the specimen’s compression at different water contents further affects its physical and mechanical properties are not fully understood yet. In this study, polycrystalline rock salt specimens were prepared under nominally dry and wet conditions and some of the dry and wet specimens were annealed after the preparation. The relationship between the porosity of the specimens and the logarithm of the applied axial stresses during the 1D compression was found to follow a linear relationship after reaching unique critical porosities of 32% and 37% for the dry and wet specimens, respectively. Unloading and reloading the specimens did not result in any major changes in the porosity of the specimens. The specimens compressed under wet condition showed an average final porosity of 2.6% compared to 6.9% for the dry specimens. The dry and wet specimens that were annealed after the compression exhibited a lower porosity in comparison to the dry and wet specimens, respectively. Unconfined compression experiments on the specimens showed dry and wet specimens possess averaged unconfined compressive strengths (σu) of 64.3 and 16.2 MPa, respectively. Annealing decreased σu of the dry specimens to 39.6 MPa and increased σu of the wet specimens to 41 MPa.