Influence of a Pre-consolidation Treatment on the Desalination Effectiveness of a Highly Deteriorated Granite Façade of Medieval Age

Abstract

ABSTRACT In this study, the pre-consolidation of the granite used in the north façade of St. Martin’s Cathedral in Ourense, of Romanesque style (S. XII–XIII), and its influence on the effectiveness of a subsequent desalination treatment using poultices of different composition is presented. The need for both treatments lay in the high degree of deterioration of the granite of the façade, which suffers an intense sand disaggregation associated with salt crystallization. The effectiveness and harmful effects of the pre-consolidation using a conventional TEOS (Estel 1000) and a nanoconsolidant based on silicon oligomers (UCAD-2o), initially under laboratory conditions and later on site, were evaluated. In situ desalination was performed applying different types of poultices chosen taking into account the pore distribution of the pre-treated granite. The obtained results, both in the laboratory and on-site, show that the pre-treatment of the deteriorated granite with UCAD-2o restores the necessary cohesion to the rock to be subsequently desalinated, increasing—compared to the other consolidant—the efficiency of desalination through the higher reduction in the granite’s pore volume with capillary access diameter. This research contributes new data to improve the most serious conservation problems that affect granitic monuments affected by soluble salts, when the intense sand disaggregation process complicates the desalination due to the risk of loss of surface material.