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Complex pore geometries in natural build ing stones: an experimental and theoretical approach for the modeling of porosity changes in natural, degraded and treated calcarenites
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Effectiveness, compatibility and durability of consolidants for marble: a review of the last ten year of researches
Full text linkThe choice of suitable consolidant treatment for cultural stones is one of the main challenging issue for conservation and protection of ancient masonry. Among building materials, marble is one of the most used for building and sculptures. Due to its low porosity, the assessment of suitable treatment for marble consolidation is not trivial; beside, the type of product, treatment methodology, effectiveness and compatibility investigation and durability monitoring have to be taken in great account. Recently, researchers have extensively tested and proposed new products for consolidating carbonate stones, including organic and inorganic products, nanoparticles, biological organisms (De Muynck et al., 2010). Nevertheless, no entirely satisfactory treatment is currently available for marble consolidation. At the same time, no unique evaluation criteria to use as laboratory estimators of consolidating performances have been assessed . The present paper aims to carry out a review of the state of art, based on the last ten years of researches, on consolidants for marble substrate. We summarize the different type of commercial and research products proposed for marble consolidation, by comparing also effectiveness, compatibility and durability of each proposed product, in function of consolidant features (i.e., product concentration, solvent type) and treatment methodology (application process, and contact time)
Visualization and quantification of weathering effects and water uptake processes in natural building stones by using neutron imaging
Full text linkCalcarenites are the most widely used natural building stones in Sicily. They are frequently subjected to very intense degradation due to salt growth [1, 2]. This process is often responsible for strong modifications of their pore network [3] and has a great influence in the mechanical properties and the durability of materials [4]. In addition, as water transport has a key role in the degradation processes, the quantification and visualization of fluidflow into the pore network of degraded stones represent useful tools in understanding the weathering process.
Classical approaches are usually performed by applying laboratory test routines for the determination of water absorption parameters. However, they cannot provide a description of the local distribution of water inside the stone. In this framework, neutron imaging has been demonstrated as a powerful technique for the visualization and quantification of the water distribution in partially saturated porous media [5]. Moreover, the possibility to perform dynamic measurements allowed monitoring the water uptake as function of time and to explore the complex processes involved in fluid transport [6-8].
In this study neutron radiography has been used with the aim of: a) monitoring and visualizing the fluidflow patterns inside porous structure of a local calcarenite widely used as building and replace stone in several Cultural Heritages, namely Sabucina Stone; b) quantifying the water distribution as function of time, in order to understand the effects of weathering on the behavior of the stone against water. In detail, samples of un-weathered and artificially weathered[9] Sabucina Stone have been scanned with neutron imaging technique at the IMAGINE beam line located at the Laboratoire Léon Brillouin (CEA/CNRS) in Saclay (France). Capillary water uptake has been monitored over time in samples subjected to different salt crystallization cycles.
Beside the qualitative data acquired from the raw neutron images (Figure 1(a)), quantitative results have been obtained thanks to the image processing of the radiographs (Figure 1(b)) [10]. First of all, the evolution of the wetting front position over time has been observed and the penetration coefficient has been determined. The results demonstrated that changes in the hydric properties of the stone occurred with the intensification of the degradation process. Even if a good agreement with standard capillary absorption test has been obtained [11], the non-perfect linearity of capillary uptake process has been evaluated, due to the evidence of preferential flow paths. Therefore, neutron images have been processed in order to obtain quantitative water distributions as function of time. The contour plot of the water content value highlighted that degraded stones absorbed greater volumes of water than the un-weathered ones, due to the strong modification of their pore structure. Moreover, in weathered samples the quicker and deeper vertical spreading of the water was associated with an intense horizontal migration through pores enlarged by the degradation mechanisms. Finally, side effects, probably due to the more intense action of the degradation process close to the sample surface, were evidenced, determining different capillarity absorption properties for the inner and surface regions. In conclusion, neutron radiography has allowed a better understanding of the deterioration mechanisms affecting physical properties of building stones, supplying relevant data for planning powerfully actions to improve their durability. References:
[1] M. Steiger, S. Asmussen. Geochimica et Cosmochimica Acta2008; 72: 4291.
[2] G.W. Scherer. Cement and Concrete Research1999; 29:1347.
[3]S. Raneri, V. Cnudde, T. De Kock, H. Derluyn, G. Barone, P. Mazzoleni. Europen Journal of Mineralogy2015; 27: 279
[4] S. Yu, C.T. Oguchi. Engineering Geology2010; 115: 226.
[5] E. Perfect, C.L.Cheng, M. Kanga, M.Z. Bilheux, J.M. Lamanna, M.J. Gragg, D.M. Wright. Earth-Science Reviews2014; 129:120.
[6] G. Barone G, V. Crupi, F. Longo, D. Majolino, P. Mazzoleni, S. Raneri, J. Teixeira, V. Venuti. Journal Instrumentation2014; 9: C05024.
[7] V. Cnudde, M. Dierick, J. Vlassenbroeck, B. Masschaele, E. Lehmann, P. Jacob, L. Van Hoorebeke. Nucl.Instrum. Methods Phys. Res. B 2008; 266:155.
[8] M. Dierick, J. Vlassenbroeck, B. Masschaele, V. Cnudde, L. van Hoorebeke, A. Hillenbach. Nucl.Instrum.Methods Phys. Res. A2005; 542:296.
[9] UNI EN 12370, Natural stones test methods: Determination of resistance to salt crystallisation, UNI ed., Milano, 2001.
[10] F.H. Kim, D. Penumadu, D.S. Hussey. J. Geotech. Geoenviron. Eng.2012; 138:147.G.
[11] G. Barone, P. Mazzoleni, G. Pappalardo, S. Raneri. Construction and Building Materials2015; 95:355
TOWARDS A TUSCANY ANCIENT CERAMIC DATABASE: THE "OPEN FABRICS" PROJECT
No full textThe identification of the provenance of ancient potteries as well the raw materials employed in different workshops is one of the main aim of the archeoceramic studies, involving both archaeology and archaeometry disciplines. In these framework, the correct evaluation of these aspects, cannot disregards the availability of reference groups having certain provenance and clays database; the experimental archaeology can also provide fundamental insights, producing laboratory samples by using known raw materials to verify feature of ceramics made with reference clayey sediments. The archaeological and archaeometric studies of ancient ceramics and laboratory samples provide, usually, a large number of dataset, including typological and stylistically analysis, as well the results of petrographic, mineralogical and chemical studies. However, all these dataare mostly published in single scientific contributes, sometime providing only some examples and/or partial results, so that the comparison between a new set of archaeological findings and already studied materials is quite difficult. In the last ten years, archaeologists and archaeometrists had proposed some tentative of centralization of the results, for a easy and quickly comparisons of ceramic materials on regional or national scale, by using geomatic tools [1-5]. In this streamline is framed the "Open Fabrics" Project [6], finalized to collect, for the first time, in a unique free and open database, a wide unpublished dataset about ancient ceramics from numerous archaeological sites in Tuscany with dating ranging from Late Antiquity to Middle Age; the database take also advantage from data about laboratory samples produced by experimental archaeology routines by using clays samples from the most suitable local geological sources to manufacture ceramic materials. The database, currently under construction, is managed by using Microsoft Access database and it is characterized by a great flexibility, being expandable for its implementation with multidisciplinary studies. Following the principle of GIS tools, the access to the database will allow to the usera easily comparison of studied ceramics by queries regarding both archaeological and archaeometric features. Each target (i.e. archaeological artifact) included in the database is geo-referenced, allowing a global overview on the distribution of a certain archaeological/fabric type over the regional context; it is also provided by both typological description and results of archaeometric analysis (fabric classification, mineralogical and chemical composition by X-ray fluorescence analysis). Apart from ceramic objects, the database includes as target also clays sources, each of them providing geological and geochemical characterization and geolocalized in respect to a geological map level. In this contribute, we propose the architecture of the database and its working principle, along with some data already loaded in.
REFERENCES:[1] A. Hein,V.Kilikoglou (2012) ceraDAT—PROTOTYPE OF A WEB-BASED RELATIONAL DATABASE FOR ARCHAEOLOGICAL CERAMICS, Archaeometry, 54, 230-243. [2] S. T. Levi, V. Cannavò, D. Brunelli, A. Di Renzoni (2015) Wikipottery: Archaeometric and archaeological catalogue and classification of Central Mediterranean Prehistoric Pottery, 2015. [3] J. B. Barreau, B. Gehres (2015) BasePetroCeram: a database for petrographic and geochemical analysis of archaeological ceramics, EMAC 2015 - 13th European Meeting on Ancient Ceramics, Athenes, Greece. [4] Facem Project, first release 2011, sixth release of FACEM of December 6th, 2016 (http://facem.at/). [5] Roman Amphorae: a digital resources (http://archaeologydataservice.ac.uk). [6] F. Cantini, B. Fatighenti, M. Gabriele (2015) O(pen) F(abrics): un portale di impasti on-line, in P. Arthur, M. L. Imperiale (2015) VII Congresso di Archeologia Medievale (Lecce, 9-12 settembre 2015)
Evaluation of the technological features of late roman cooking ware classes from Akrai (Syracuse, Sicily)
Full text linkIn this work, a provenance and technological investigation on cooking-ware potteries from the ancient
Greek -Roman town of Akrai (Palazzolo Acreide, Syracuse, Sicily) has proposed. A multi-methodological
approach have been used to study the manufacture quality of analysed materials; in detail, petrograp
hic, mineralogical, spectroscopic, chemical, porosimetric and micro-morphological analyses have been
applied. The study providesfundamental contribute in archeological issues related to circulation in Sicily of cooking
-ware productions during Late Roman Age; in fact, the obtained results allow to recognize in the site
the presence of different well-known cooking-ware Roman productions, highlighting interesting questions
about the technological and manufacture properties of this class of materials
Artificial neural network for the provenance study of archaeological ceramics using clay sediment database
Full text linkAn artificial neural network (ANN) for archaeometric studies was created to facilitate provenance attribution of archaeological ceramics. A multilayer perceptron model (MLP) was applied to construct the network, including only one hidden layer. Moreover, correction parameters based on historical and archaeological evidences were applied to Bayesian probability factor. The ANN was trained by using clays mixings mathematically constructed based on a reference chemical database of Sicilian sediments. The clay mixing takes in consideration compositional variability within the same geological site and the extent of the ceramic manufacture processes. Test was performed by querying the ANN with compositional data of ceramics found in archaeological sites coherent with clays sampling areas. Up to 88% correct attribution was verified, with good correspondence between geological and archaeological contexts. Finally, merits of ANN were highlighted by comparing the extent of successfully provisional attribution with classical statistical methods (PCA and LDA)
Archeometric study of the more ancient painted wall found in Sicily (Apaforte – Licata)
No full textIn the present work, an analytical study of painted plaster samples coming from an ancient crypt, dated back to 4th – 3rd cent B.C. and located in Licata (Sicily, Southern Italy), has been carried out. This crypt situated in the street called “c.daApaforte” is an interesting hypogeum composed of a single room made of stone blocks. The importance of this crypt is represented by the presence of the most ancient painted wall recovered in Sicilian hypogea structures.
In order to identify the pigmenting agents, the preparation layers and the deterioration processeswe carried out non-destructive micro-Raman spectroscopy and micro-destructive analyses through SEM-EDS. Preliminary characterization of samples was done by optical microscopy (OM).
The micro-Raman measurements have been performed in order to investigate the molecular nature of the used materials and obtain a preliminary characterization of the decorated surfaces. The quantitative analysis of the chemical composition of the different layers (pigments, preparation layers, deteriorated parts) has been obtained by SEM-EDS.
Finally, preliminary macroscopic and thin section analysis have been carried out with the aim at characterizing plaster features and degradation processes.
In order to establish the production technique used by the craftsmen, the results were compared with our recent data on Hellenistic plasters coming from an ancient buildings located in Licata and dated back 2ndcent B.C (Aquilia E. et al., 2012)
Building materials and cultural models in late Roman Tuscany: archaeometric studies on stones, mortars and vitreous tesserae from “Villa dell’Oratorio”(Capraia e Limite, Florence)
No full textConservation of cultural stones: relationship among texture, thermal ageing and consolidation strategies in white Apuan marbles
Full text linkA major problem in the conservation of stone materials concerns durability and the use of compatible and
efficacy conservation treatments. Among cultural stones, white Apuan marble stands out for its wide diffusion in built
environment; thus, the study of its decay and the recognition of smart solution for its conservation is a quite relevant
issue. In spite of an aesthetical homogeneity, white marbles exhibit a range of textural features able to influence their
durability. The aims of this study are therefore to evidence the relationship between decay and textural features in
marbles, and to test the efficacy of some innovative nanostructured products in comparison to ethyl-silicate. Ten white
marbles from different Apuan Alps quarrying areas, characterized by a range of textural features, were analyzed.
Preliminary, textural, mineralogical and chemical analysis have been performed by petrographic, XRD, and XRF
analyses; physical properties were determined by both capillarity and water absorption by total immersion tests on
specimens. After an initial drying at 60±5°C, specimens were artificially aged by thermal stresses (cycles at 110°C,
110°C and cooling in water, 250°C, and 550°C). The comparison of physical parameters before and after thermal
stresses allows evaluating the influence of some textural factors (especially grain boundaries and mean grain size) on
the decay. Artificially thermal damaged samples were subsequently treated with two nanostructured products, nano-lime
and nano-silica, and with ethyl-silicate, to compare the efficacy of innovative consolidants in respect to a traditional one.
The efficacy was evaluated on the basis of water absorption behavior of marbles before and after treatments. The study
evidenced better performances of nano-silica in respect to nano-lime, even ethyl-silicate confirmed its high effectiveness
in consolidating marbles regardless their textural features
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