Environmental Impact Assessment On The PorousStone Masonries Of The Rethymnon Fortress

Abstract

The weathering of monuments, considered as interaction between building materials and environmental factors, presents specific interest in the case of the marine environment in the mild climatic conditions of the Mediterranean. An extended monument, like the Fortress of Rethymnon could well serve as an example. It is constructed by a susceptible to salt decay biocalcareous porous stone and suffers mainly from salt crystallization and hard carbonate crust formation. The research program develops on various masonry surfaces, as far as position and exposure orientation to various environmental factors are concerned mainly regarding humidity sources like groundwater's capillary rise and marine salt spray. Stone specimens from various positions along the Fortress, characteristic of the various decay patterns, underwent mineralogical and microstructural examination. Digital image processing is performed on characteristic surface images from the Fortifications, acquired from photograms and restituted in false colors, in order to assess and evaluate the environmental impact to the masonries according to the physicochemical criteria employed for the weathering classification (microstructure, texture and composition). Digital image processing is proved to be a reliable automatic mapping method for environmental impact assessment on extended masonry surfaces, when the conversion of the varying surface energy contents renders and distinguishes the microstructural and textural characteristics of weathered stones. Hence, a sound basis for interdisciplinary scientific conservation planning is provided.