Performance in use and conservation
Published:January 01, 2007
The petrophysical characteristics of a building stone used in the city of Pavia, northern Italy, are analysed in the light of stone conservation through the application of water repellent and consolidant products. The research focuses on the modification of petrophysical properties as a function of the applied products, and on the critical assessment of the performances of fluorinated and siloxane resins as a function of the variable nature of the same lithotype. The studied material is a calcareous sandstone (Mt Arzolo Sandstone), Late Miocene–Early Pliocene in age, extensively employed as a building material during the 11th and 12th centuries. Experimental investigations on samples from historic quarries were performed before and after application of treatments: i.e. petrographical and fabric analyses; ultrasonic measurements; mercury porosimetry; abrasion resistance measurements; contact angle measurements; capillary and low-pressure water absorptions; water vapour permeability; and colour measurements. Two main lithotypes of Mt Arzolo Sandstone were recognized according to their petrophysical features: the open porosity being similar, differences exist concerning their fabric. These differences influence the physical–mechanical properties of the material and consequently the performances of the applied products. In particular, the difficulties in penetration of products when sandstone of smaller pore size is treated can lead to a significant reduction of the overall performances, which is more evident for products containing organic solvent with high molecular weight.
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Building Stone Decay: From Diagnosis to Conservation
Stone buildings and monuments from the cultural centres of many of the world's urban areas. Frequently these areas are prone to high levels of atmospheric pollution that promote a variety of aggressive stone decay processes. Because of this, stone decay is now widely recognized as a severe threat to much of our cultural heritage. If this threat is to be successfully addressed it is essential that the symptoms of decay are clearly identified, that appropriate stone properties are accurately characterized and that decay processes are precisely identified. It is undoubtedly the case that successful conservation has to be underpinned by a comprehensive understanding of the causes of decay and the factors that control them. The accomplishment of these demanding goals requires an interdisciplinary approach based on co-operation between geologists, environmental scientists, chemists, material scientists, civil engineers, restorers and architects. In pursuit of this collaboration, this volume aims to strengthen the knowledge base dealing with the causes, consequences, prevention and solution of stone decay problems.