How not to bother salts while grouting

Abstract

The objective of this research work was to assess if the injection of water-reduced grouts (water-ethanol-based) mobilises soluble salts to a lesser extent compared to the injection of conventional water-based grouts. Ethanol was used as a partial substitute for water in grouts preparation, being a poorer solvent for soluble salts when compared to water. Three injection grouts were evaluated; for each grout individually, the performance of mixtures prepared with 100% water was compared to the performance of the same grout prepared with water-ethanol. To assess the different performance in a salt loaded system, the grouts were tested into replicas of delaminated plaster intentionally contaminated with NaCl. The salt movement was followed by evanescent field dielectrometry using the SUSI© instrument. Grouts with reduced water content were also tested on site, at the San Vincenzo Oratory in Pazzallo, Tessin (CH), on decorated plasters afflicted by severe delamination associated with high amounts of soluble salts. Two adjoining areas, comparable in condition and in salt content, were stabilised with the same grout differing only in the nature of the suspension medium used (water-ethanol vs. water). Both in the laboratory and on site, it was experimentally verified that water-ethanol-based grouts caused a significant reduction of salts mobilisation, bothering salts to a lower extent compared to a typical water-based grouting intervention.