Influence of the properties of granite and sandstone in the desalination process by electrokinetic technique

Soluble salts are considered a main cause of damage of porous building materials such as rocks, bricks or granites, which were commonly used in the building constructions of the architectural and archaeological heritage. Soluble salts are also responsible for various forms of deterioration such as sand disaggregation and superficial detachments. These problems can be solved by conservation technologies, which are aimed to decrease the salt concentration in rocks (desalination).The present study aimed to investigate the efficiency of electrokinetic techniques for desalination of two different kinds of rocks: granite and sandstone. These rocks were contaminated with NaCl solution, and samples with a thickness of 6 cm were used in the tests. This study compared the percentage of salt removal at different depths (efficacy) and the time needed to get the same percentage removal (effectiveness) achieved in both stones.From the results obtained, it was possible to find those inherent factors to each stone which could have an influence on the efficacy of the treatment. With this technique it was possible to reduce the salt concentration in the granite almost to 100%. However, in the sandstone samples the decreases were not equally high, mainly at the intermediate levels where slight enrichments were observed. The results indicate that although the used technique is efficient for salt removal regardless of the porosimetric distribution of the rock, the better interconnection between the pores in the granite samples (favored a faster desalination process).