Alteration of sidi ghanem mosque limestone. influence of the lithological nature and the environmental conditions

Abstract

Over time and under exposure to atmospheric agents,the monumental stone are exposed to physicochemical mechanismswhich generating alterations. These alterations destroy the monuments’ surfaces, and eventually may affect the supporting structure and its stability. In this article we studied:a) the influence of the sequence of humidification anddryingon the alteration of the Sidi Ghanem Mosque limestone;b) a morphological, petrographic, mineralogical, chemical and petrophysical characterisation on the stone; c) temperature and humidity measurements inside the mosque for one year by means of thermo-hygro-bottons followed by d) an aging test through cycles of humidification and drying on the unaltered stone. The results presents: a) the stratigraphic composition and the condensation of water on the surfaceof the stone andb) the diffusion through the porous network of the stone,as well as its drying have led to the formation of ferrichydratesFe2O3·H2O. This ferric hydrate is a complex form of iron oxide which represents rust of ocher color and that thickness of the altered part depends on the penetration depth of air and water