Comportamento da Migração de Íons Cloreto do Substrato para Argamassa de Saneamento, Desenvolvida para Recuperação de Prédios Históricos

Abstract

The deterioration of civil construction materials, in aggressive environments, as is the case in the extreme south of the country, is intense due to the coastal and port region, in addition to industrial operations, strong winds and a severely maritime environment. Soluble salts and moisture are the main causes of degradation in masonry structures in this type of environment. Sanitation mortar, not commonly used in Brazil, but quite widespread in Germany, is a material that has been showing relevant and satisfactory results in civil construction. This highly porous material allows the migration of saline contamination from the masonry to the sanitation mortar and its consequent crystallization without damaging the coating. In Brazil, it is still precarious to determine techniques capable of dealing with the migration and crystallization of soluble salts in mortar coatings in masonry and structures. In Rio Grande, in the state of Rio Grande do Sul, deterioration of mortar coatings and the emergence of other pathological manifestations resulting from the characteristics of the environment in relation to salinity and humidity is common. Therefore, an attempt was made to apply a sanitation mortar, used for the recovery of historic buildings in the city of Rio Grande, to conventional masonry completely saturated with soluble salts and to observe the behavior of chloride ions along the depth of penetration of the microstructure of the coatings in three, five and seven centimeters thick. Thus, to analyze whether the sanitation mortar coating, in different thicknesses, used on conventional masonry substrates, highly contaminated with these ions, has the behavior of final recovery plaster. The methodology for contamination, curing, substrate coating, sample extraction, sample treatment and analysis of the migration of chloride ions from the substrate to the sanitation mortar followed the few existing bibliographic references in Brazil and the recommendations of the German WTA. The obtained results showed the main characteristics of the sanitation mortar in relation to its fresh and hardened state and several behavioral profiles of the migration of chloride ions from the substrate to the sanitation mortar in its different coating thicknesses. It was concluded that the sanitation mortar needs certain care in its use due to its low tensile strength in flexion and compression. However, it showed excellent results in terms of application in environments with a marine atmosphere for thicknesses of three and five centimeters, fulfilling its role in retaining chloride ions, preventing deterioration due to moisture and salts. Initially, the seven centimeter-thick coatings did not perform well, not being indicated for recovery renders. The good performance of the coating will depend on the thickness and its ability to retain soluble salts in coastal, coastal and port environments.