This paper focuses on the characterization approach to evaluate the decay state of Pietra Serena of historic buildings in Florence (Italy). Pietra Serena is a Florentine sandstone largely used in the city especially during the Renaissance; it is a symbol of cultural heritage of Florence and constitutes a large part of the city center, which was named a World Heritage Site by UNESCO in 1982. Unfortunately, many environmental factors negatively affect the stone, increasing damage and the danger of falling material. Any detachment of stone fragments, in addition to constitute a loss in cultural heritage, can be dangerous for citizens and the many tourists that visit the city. The use of non-destructive techniques (NDTs) as ultrasonic and Schmidt hammer tests can quantitatively define some mechanical properties and help to monitor the decay degree of building stone. In this study, the NDTs were combined with mineralogical, petrographical, chemical and physical analyses to investigate the stone materials, in order to correlate their features with the characteristics of the different artefacts in Pietra Serena. Correlations between the NDTs results and the compositional characteristics of the on-site stone were carried out; such discussion allows to identify zones of weakness and dangerous unstable elements.
This paper investigates the influence of natural organic materials on the properties of traditional mortars. Mortar specimens produced with two binders (natural hydraulic lime and aged lime putty) with the same sand and three different organic additives (linseed oil, brown sugar and cow's milk, with different percentages) were created. The colour variations (colorimetry), waterproofing behaviour (water capillarity test), permeability (water vapour permeability test), mechanical properties (maximum resistance to compression test), mineralogical composition (X ray diffraction) and optical properties of mortars (transmitted light microscopy, UV fluorescence microscopy) and carbonation using a phenolphthalein indicator, were evaluated after 28 days, 3, 6, and 12 months.In this paper we highlighted a series of transformations induced by the additives: a strong modification of colorimetric parameters, a general hydrophobic effect of milk and oil not linked to a total occlusion of porosity, a decrease of mechanical parameters in the specimens prepared with hydraulic lime with respect to the specimen without additives, a different distribution and shape of macropores, a different level of carbonation.
3The paper also describes the role of the preparation methods in the influence of natural organic materials on the properties of traditional mortars.
The study of structural masonry joined to geohydrological hazards in cultural heritage represents a multidisciplinary theme, which requires consideration of several aspects, among them the characterization of the materials used. In this paper, a first complete chemical, minero-petrographic, and physico-mechanical characterization of core samples taken from the masonry of two Florence riverbanks (Lungarno degli Acciaiuoli and Lungarno delle Grazie) is performed in order to identify the raw materials, technologies, and state of conservation and to support the planning of maintenance and restoration interventions. The physico-mechanical characterization of the riverbanks allows their stability to be determined. Such investigations allow identification of the level of compactness and cohesion of masonry; this information is useful for planning emergency interventions and for supporting planned restoration activities. The results provide valid support for the design of riverbank safety projects, to mitigate the risk of their collapse and to decrease the flood risk in the historic center of Florence.
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