Author(s)

M. Radeka, J. Kiurski, S. Markov, R. Marinković-Nedučin & J. Ranogajec

Abstract

The study illustrates both the biodeterioration and biomineralization actions of two fungus species (Aspergillus niger and Cladosporium sp.) and two organic acids (oxalic and acetic) and the action of the frost (frost dilatation studies in laboratory conditions) as the main factors of the process of ageing of clay roofing tiles. The nano-crystalline products, formed in this way, contribute to the abundant reactive surface area of the existing and new filled pores (due to the fungus hyphen penetration into the ceramic support) deepening the ageing processes of the clay roofing tiles. A relationship between the textural and microstructural characteristics of the studied systems and the formation of the specific crystal forms, developed after the actions of fungus, and oxalic/acetic acids was set up. Keywords: biodeterioration, lichen, fungi, oxalic acid, acetic acid, clay roofing tiles. 1 Introduction Cultural heritage objects were made with almost all type of materials produced by nature and used by men to realize several types of artefacts of very simple mono-components and of complex structure, integrating inorganic and organic matter. These objects, even if they were made of more \“resistant” stones, mortars and ceramic materials, are influenced by the environmental parameters, which can modify their structure and composition. Furthermore, inserted into the \“biosphere” they can be decayed by biological mechanisms. Clay roofing tiles, as a part of this world, support large and diverse communities of microorganisms that colonize both the tile surface and the porous interior. Their weathering, as a result of organic acid exudation by lichens, fungi and bacteria, is recognized as a

Keywords

biodeterioration, lichen, fungi, oxalic acid, acetic acid, clay roofing tiles.