Abstract
The pathologies formed in slate roofs are mainly due to the presence of potentially unstable minerals (iron sulfides, carbonates and organic matter). These minerals may become altered by the effect of environmental agents, once the slate roof is finished. The pathologies are mainly associated with oxidation and gypsification processes of the cited mineral phases. In this work, the potential pathologies of several Spanish roofing slates are identified, using the tests defined in the European Norms EN 12326:2005, 14147:2004 and 11597:2007.
Highlights
As a building material, there are several different pathologies that may affect roofing slate, among which the most important, in terms of their negative impact (*) Universidad de Oviedo. (**) Universidade de Santiago de Compostela (A Coruña, España).and frequency, are oxidation and gypsification
Frequency, are oxidation and gypsification. Both pathologies are closely related to the presence of minerals prone to chemical alteration, such as iron sulfides and organic matter, and carbonates, which may react with environmental elements once a slate roofing tile has been put in place
The oxidation of iron sulfides (1, 2) produces reddish rust marks on the surface of the slate; as such, slates that contain these minerals cannot be classified as top quality commercial products, even if the rest of their physical and mechanical properties are optimal
Summary
There are several different pathologies that may affect roofing slate, among which the most important, in terms of their negative impact (*) Universidad de Oviedo. Both pathologies are closely related to the presence of minerals prone to chemical alteration, such as iron sulfides and organic matter (oxidation), and carbonates (gypsification), which may react with environmental elements (sun, rain, atmospheric pollutants, etc.) once a slate roofing tile has been put in place. Gypsification, on the other hand, may affect the inner cohesion of the slate tiles, due to the growth of gypsum crystals between the phyllosilicate sheets that make up the slate, making it more harmful than oxidation. During the quarrying process, levels with high concentrations of alterable minerals are dumped directly into the tailings, which substantially hinders the performance ratio, and sharply worsens the environmental impact of slate mine tailings (4, 5)
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