1,721,005 research outputs found
L’architetto restauratore e l’esperto dei materiali. Esperienze didattiche come occasione di riflessione su interazioni, competenze e ruoli
No full textThe joint teaching experience in the Architecture MSc courses, focusing on the reuse and functionalization of built heritage in historic context, constitute an important occasion to reflect about the relationship between architect restorers and material experts. The topic of interdisciplinary teaching and proposed contents is currently under discussion on the international scene. The integration of the disciplines related to the project with STEM disciplines, is a rather new argument. The Italian academic scientific sector “Material Science and technology” looks at the materials’ behav- iour under different stresses and the interaction with the environment. Interdisciplinary knowledge should find a syn- thesis in the questions of the conservation and reuse project. The experience of a MSc level course at Politecnico di Milano, is described and discussed as a paradigm of a fruitful and innovative collaboration able to train good and aware professionals for the intervention in historical contexts
Artificial ageing of photocatalytic nanocomposites for the protection of natural stones
Full text linkDuring the last ten years, photocatalytic nanocomposites combining titania nanoparticles with silicon-based matrices have received increasing attention in the stone conservation research field, because they oer an eective multifunctional approach to the issue of stone protection. However, much work still has to be done in studying the behaviour of these nanocomposites in real environmental conditions and understanding to what extent they are able to retain their eectiveness and compatibility once applied on outdoor surfaces. The latter is a key information that should lie at the basis of any successful conservation and maintenance campaign. The present study provides insight into this relevant topic trough laboratory testing by assessing the artificial ageing of two silane-based photocatalytic nanocomposites, previously selected through an accurate testing on dierent natural stones. Three accelerated ageing procedures, based on artificial solar irradiation, heating and rain wash-out, allowed simulating about two years of outdoor exposure to some of the weathering factors to which stones are normally subjected. The results provided quite accurate information about the long-term behaviour of the products and on the role that the stone properties play therein. It was shown that, when the products are able to penetrate deeply enough inside the stone pores, they retain much of their hydrophobising and photocatalytic properties and maintain a good compatibility with the stone substrates, even after partial chemical degradation of the alkyl-silica matrices has occurred on the very stone surface
Study of "green" inhibitors on copper alloy artefacts
No full textIn order to preserve the surfaces of the metallic artworks from corrosion and degradation, protective systems containing corrosion inhibitors are often applied. These systems must fulfil strict requirements of non-invasiveness from the aesthetic point of view, and shouldn't be dangerous for humans and environment. Benzotriazole (BTA) is the inhibitor usually employed for copper alloys, however it is suspected to be harmful for humans and environment. For this reason, in the last years several "green" alternatives were proposed. In this work, the performances of a selection of green inhibitors have been evaluated. They were applied on polished and artificially patinated copper, an on bronze with natural and artistic artificial patinas, in consideration of the large variability of surface conditions that can be found in cultural heritage field. Their inhibition efficiency was evaluated with electrochemical techniques, while their influence on the surfaces appearance was assessed by means of spectrophotometry in visible light
Optimisation of the setup of LPR and EIS measurements for the onsite, non-invasive study of metallic artefacts
No full textElectrochemical techniques have been successfully applied in the past as non-destructive techniques to the cultural heritage field. In particular, linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS) have been employed for the onsite monitoring of corrosion on metallic works of art, providing valuable results. Such techniques have been successfully adapted from the industrial field for this particular kind of application, but a systematic evaluation of the influence of all experimental settings on the obtained results is still lacking: several factors and parameters can affect the results, and it is important to properly consider their influence for a reliable interpretation of data. Therefore, in this work, the influence of a series of experimental parameters was evaluated in order to obtain a reliable and time-effective setup by performing a series of tests on a bronze artefact. Several variables were considered, with particular attention to those affecting the reproducibility and reliability of the measurements, as well as the duration of each single acquisition. It was demonstrated, in fact, that an optimised experimental setup from the point of view of the duration could improve also reproducibility and reliability of the measurements. The optimised protocol was then adopted in the framework of a diagnostic campaign of the Monumento ai Caduti (War Memorial) of Lecco (IT
Methodological challenges for the investigation of the dual role of biofilms on outdoor heritage
No full text: Biofilm deterioration and biofilm protection should be considered as different aspects of the complex interactions between microbes and the surfaces of outdoor heritage (e.g. stones, bricks, mortar and plaster). Thus, it is urgent to verify and quantify to what extent the biofilm can protect from different weathering processes, to eventually determine the advisability of biofilm removal from the heritage surfaces. On one hand, it is necessary to more precisely describe the decaying processes caused by the microorganisms and to quantify the extent, severity, and rate at which the microorganisms are causing the decay. On the other hand, it is necessary to define methodologies to comprehensively study the bioprotection phenomena. So far, no decision-making tool is available to guide heritage professionals in deciding whether to remove or keep biofilms on heritage surfaces, and aesthetical alteration and discoloration is often the only criterion considered. In this work the different available approaches for the study of the dual role of biofilms on outdoor heritage have been critically reviewed. The open challenges and questions are also summarised
Effects of cleaning procedures on the long-term corrosion behavior of bronze artifacts of the cultural heritage in outdoor environment
Full text linkThe cleaning of metallic artworks is a crucial step for their preservation. Cleaning operations generally aim at removing deposits and corrosion layers, and all the non-stable and potentially reactive phases formed as a consequence of the interaction of the metal with the environment. Thus, all secondary-formed compounds and layers that can undermine the overall preservation of the artwork, both from the esthetic and the corrosion point of view, should be removed. On the other hand, superficial stable patinas contributing to the artistic and historic value of the objects and that may provide protection to the metallic surface should be preserved. The optimal cleaning procedure should be able to promote a long-term improvement of the corrosion resistance of the surfaces. Therefore, the long-term monitoring of the corrosion behavior of the cleaned surfaces with electrochemical techniques could provide valuable information for the selection of the optimal methodology. In this work, five cleaning procedures have been applied to five bronze sculptures. The cleaned surfaces have been characterized following a multi-analytical and non-invasive approach, and the long-term evolution of their corrosion behavior has been monitored by means of on-site non-invasive linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements for more than 2 years
Preliminary approach to protect Street Art from environmental agents and gaseous pollutants
No full textCorrosion-induced release of Cu and Zn into rainwater from brass, bronze and their pure metals. A 2-year field study
No full textA 2-year field study has been conducted in an urban environment to provide annual release rates of copper and zinc from brass (20 wt% Zn) and copper and tin from bronze (6 wt% Sn) compared to sheets of their pure alloy constituents, copper and zinc. Despite relatively low nominal bulk alloy content, substantially more zinc was released from brass compared to copper. Both metals were released at a significantly slower rate from the brass alloy, compared to the pure metals. The proportion of release rates of copper and zinc from the alloy differed significantly from their proportions in the bulk alloy.
Bronze showed relatively constant release rates of copper, being similar to that of pure copper sheet. The release of tin from bronze was negligible. The results clearly show that alloys and the pure metals behave very differently when exposed to rainwater. Accordingly, release rates from pure metals cannot be used to predict release rates of individual constituents from their alloys. Generated data are of importance within REACH, the new chemical policy of the European commission, where metal alloys erroneously are being treated as mixtures of chemical substances
Semi-empirical models to describe the absorption of liquid water in natural stones employed in built heritage before and after the application of water repellent treatments
Full text linkThis study aims at validating an easily implementable and effective methodology to simulate the capillary imbibition rate of porous building materials, with special attention to stones employed in historical architecture. Two models selected from the literature are discussed from both a theoretical and practical viewpoint and their effectiveness in describing the imbibition process is evaluated on a large set of water absorption data of four different natural stones. It is shown that these models can be used in a predictive way to calculate the sorptivity of stones with fairly good approximation. Furthermore, they may represent a useful tool for the study of porous materials of built heritage, since, contrary to standard tests for sorptivity determination, they only require small samples to determine the pore size distribution and the maximum water saturation of the investigated materials. Finally, it is shown that the same models can also be used to simulate the reduction in water absorption after the application of water-repellent products, affording some insight into the protection mechanism and the criteria that determine the performance of protective treatments
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