Electrokinetic desalination of protruded areas of stone avoiding the direct contact with electrodes

Abstract

Soluble salts are considered one of the main deterioration factors of porous building materials such as rocks, bricks or granites. The desalination treatments currently used in order to mitigate this alteration process are usually applied directly on the affected areas, which have often a low degree of cohesion precisely due to the deteriorating effect of the salts. The present study aimed to investigate the evaluation of a new approach based on electrokinetic techniques to desalinate rocks in monuments, specifically to desalinate carved reliefs. The procedure avoids the direct contact with the areas highly affected by salts, which usually show loss of cohesion due to salt crystallization processes, by placing the electrodes on adjacent areas less contaminated with salts. This fact represents another difficulty in the desalination process because the electric field must be adapted to the shape of the sculptural motif. An ashlar of sandstone highly contaminated with salts in a protruded area located in its central part was used for this purpose. The results showed that the electrokinetic setup proposed allowed to achieve high percentages of salt content reduction (above 80 %) in the protruded area of the sandstone highly contaminated with salts. Therefore, these results confirmed that it was possible to desalinate the sandstone using electrokinetic methods without the need to put in contact the affected areas with the equipment, reducing the possibility of altering it by manipulation.