Conserving Scotland’s Built Heritage: A Petrographic Investigation on the Effects of Deicing Salts on Scottish Sandstones

In an attempt to understand the effects of high levels of de-icing salt deposition on sandstone masonry structures, samples of six blonde and two red sandstones were subject to salt crystallisation tests using three different de-icing salts. The impact of these salts on stone mass and integrity was initially evaluated by quantifying the mass gain/loss of samples via weighing and photography; subsequently Scanning Electron Microscopy (SEM), laser scanning and X-ray computed tomography scanning (CT scanning) were used to assess internal salt distributions and salt decay mechanisms across each stone type. Preliminary results indicate that both the salt type and microscopic texture of the stones play a significant role in salt accumulation within the pore structure and on observed decay characteristics. Samples immersed in CaCl2 show the greatest percentage of weight increase but with little observable decay. The red Locharbriggs samples on the other hand demonstrate the greatest percentage of weight change and decay across each salt type. This decay is related to the microscopic texture of the stone, specifically in relation to microscopic anisotropy at the pore scale.