Consolidation of Soft Sandstones Used in Historical Constructions. Application to a Case Study

The use of natural stone consolidators in historic buildings, when applicable, makes it possible to improve the internal cohesion of the stones and restore or improve the original mechanical properties that the material once had. This paper describes the in situ and lab tests on the characterization of a very porous natural sandstone used in the construction of a late 17th century Fort, located near Sines, on the south-western coast of Portugal, classified as a Property of Public Interest. Given its location, in a most aggressive environment, this construction has suffered severe degradation. A representative number of samples (stones) were taken from the somewhat degraded surrounding structures attached to the Fort. Part of these samples were subjected to a consolidation process using a commercial ethyl silicate and then submitted to physical and mechanical tests with the purpose of evaluating the consolidation action. The remaining (unconsolidated) part of the samples were subjected to the same characterization tests, for comparison. The work carried out showed the effectiveness of the consolidation treatment in reinforcing the mechanical strength of the sandstone.