Scanning Electron Microscopy (SEM) measurements were performed on dry salt samples using a FEI Quanta 200F electron microscope, equipped with an Apollo X silicon drift Detector (EDS) from EDAX. Measurements were undertaken using a back scattered electron (BSE) detector in low vacuum mode (60 Pa) at an accelerating voltage of 20 kV and a working distance of 11.5 mm for the Na 2 SO 4 and 9.4 mm for the NaCl (Fig. ). SEM images were then used for estimating the pore size distribution using ImageJ . First, the local contrast was adjusted using the CLAHE tool. Then the data was binarized and filtered using a morph open operation. On this basis, distance maps were calculated and quantified by frequency distributions of pore radii.