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1.
This study shows that the sandstone used in the construction of the Church of San Mateo in Tarifa (Cádiz, Spain) is highly sensitive to processes of decay because of a combination of factors that are intrinsic and extrinsic to the material. The mineralogy, texture and porous system of the sandstone and the proximity of the church to the sea all play a part in these processes. X-ray diffraction reveals that there are interstratified chlorite/smectite clays among the minerals that make up the rock. These mixed layer clays have been shown to undergo hydric expansion. This phenomenon may be accompanied and augmented by the presence of NaCl which acts as an electrolyte in osmotic swelling processes. Two varieties of sandstone were used in the construction of the church, namely grey sandstone and brown sandstone. The latter is more porous and undergoes greater hydric expansion, showing a higher degree of deterioration. Ultrasound analysis has demonstrated that both varieties are anisotropic because they contain bedding planes and are affected by the preferred orientation of the phyllosilicates in the rock. The anisotropic nature of these stones was confirmed by capillary suction tests. The capillary front reaches a relatively low height which means that when water is absorbed, the anisotropic textural properties combined with the presence of chlorite–smectite mixed layers in the sandstone result in mechanical (shear) stress between the first few centimetres of the wet stone and the dry area behind. The latter effect favours the development of flakes, so causing the decay of the ornamental stone and the church façade.  相似文献   

2.
The funeral monument of Maarten Tromp, in the Old Church of Delft (the Netherlands), is partially built with Tournai stone, a grey-blackish limestone from the Wallonia region (Belgium). This stone is suffering a severe delamination and scaling, which has, in the course of the centuries, led to a considerable material loss from the surface of some of the stone elements. In order to identify the damage process and define a sound basis for the conservation of the monument, a research plan was set-up including, next to the tests and analyses on the stone, a 1-year monitoring of the microclimate in the church and the investigation of the structure of the monument as well as its connections to the adjacent walls. First of all, the stone type was identified by macroscopic features and by thin section microscopy. The moisture distribution in the monument and in the adjacent walls was gravimetrically determined on samples taken at different height and depths. The content and type of salt in the Tournai stone from the monument were determined by X-ray diffraction and ion chromatography, and the results compared to those obtained for the fresh stone. The analyses showed the presence of considerable amount of gypsum, together with a low content of soluble salts (chlorides and nitrates). The SEM-EDS observations showed that gypsum is mainly crystallizing in cracks between the layers of the material. The damage mechanism and the influence of salt on the decay were further investigated by combining hygroscopic moisture uptake, hygric dilation (RH cycles between 50% and 95% RH) measurements and SEM-EDS observations; all measurements were performed both on stone sampled from the monument and, as comparison, on fresh stone specimens. The results show that gypsum is the main salt present, but its role in the damage is not significant. The naturally thin laminated structure of the stone together with the considerable hygric dilation seem to be the main causes of the delamination observed in this stone.  相似文献   

3.
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4.
This paper provides new insights into understanding the causes of deterioration of the Corbii de Piatra rupestrian church and shows the significance of studying the geological environment of historical rock-cut settlements when undertaking preservation and restoration actions. The Corbii de Piatra church is one of the few rupestrian churches remaining in Romania and is an important part of the country's heritage. The church is carved in a stratum of polymictic sandstone of Oligocene age, which is part of the Getic Depression, located in the southern part of the South Carpathians. In the 14th century the interior walls of the church were decorated with mural paintings of a high artistic value. Over the centuries, the church's walls and mural paintings have been negatively affected by a series of physicochemical processes. These processes were studied through field investigations and laboratory analyses carried out between October 2007 and November 2010. The investigations revealed that tectonic fissuring and the structural anisotropy of the rock facilitate the infiltration of meteoric water through the walls into the interior of the church, from north to south, maintaining a high-level of humidity in the northern wall and in the interior of the church. The most harmful effects observed were: (i) the partial hydrolysis of the feldspars through reaction with water from the pores, producing a friable mass of phyllosilicates which led to a superficial disaggregation of the rock and to a diminished cohesion between the rock and the mortar of the fresco, (ii) the reprecipitation of the gypsum as efflorescences on the northern wall and ceiling, covering the mural painting in localized areas, as a result of the transportation of the gypsum by water from the upper strata, (iii) the alteration of the cinnabar pigment, as a result of water penetration by diffusion through the fresco from the wet rock to the pictorial layer (the secondary effect observed being the formation of sulfuric acid, which further reacted with the carbonate from the fresco to form gypsum), (iv) the development of biotic crusts, predominately algal, on the interior wet walls, which, facilitated by the permanent high humidity and the semi-obscurity of the interior of the church, have covered large surfaces of the fresco. Compared to the interior, the exterior vertical walls have been exposed to prolonged daily and seasonal variations of temperature and humidity. These variations have caused repeated variations in the volume of the sandstone, leading to contraction fissuring and peeling of the vertical walls. Any future procedures that might be used to conserve the church should strive to reduce the humidity of the sandstone in the interior walls.  相似文献   

5.
Crystallization modifiers can significantly affect the capillary passage of dilute and concentrated solutions of sodium chloride and sodium sulfate through columns of limestone. In the absence of modifiers, sodium chloride passage through Monks Park limestone gave predominantly subflorescence with mild edge erosion while sodium sulfate mainly effloresced and severely damaged the stone column. With Texas Creme limestone, a stone of moderately higher porosity, essentially only efflorescence occurred with either salt and there was little or no stone damage. Uniquely, alkali ferrocyanides were found to impact significantly on the interaction of these solutions as they moved through the limestone. The addition of 0.10–1.00% of K4Fe(CN)6 to sodium chloride in Monks Park limestone experiments increased the flow rate of solutions through the stone, resulting in efflorescence in place of subflorescence, and yielded a massive formation of extended dendritic filaments without damaging the stone. This protection by additive was extended to sodium sulfate solutions, but only at lower salt concentrations. Results comparable to the effect of adding K4Fe(CN)6 to concentrated sodium chloride Monks Park limestone experiments were obtained with saturated sodium sulfate solutions without additives by conducting the experiments in a draft-free, high humidity environment—suggesting a potentially useful strategy for the conservation of fragile, salt-laden objects. These results are explained by factors causing evaporation of solution to occur either below or at the surface of the stone, and by the effect of modifiers on the crystal habit of the salts forming during evaporation in this region.  相似文献   

6.
基于历史档案资料,追述了伦敦大火后英国圣保罗大教堂重建时期石材采运的历史,揭示了各类石材的开采与运输方式、建造中引发的问题,并首次对石材的供应情况进行了定量分析,呈现了石材采运如何成为圣保罗大教堂的重建历时35年之久的主要原因之一。圣保罗大教堂的石材采运问题并非独特案例,同类型的石材在同时期其他建筑中曾被广泛运用,因此对研究那个时代的砖石建筑具有更普遍的参考意义。  相似文献   

7.
This study presents the results of the microclimate monitoring of the Arch of Augustus. This is a monument from the Roman era, situated in an urban area in the Western Alpine region of Aosta Valley, Italy. Measurements were carried out on different monument positions, corresponding to the four faces and below the vault. The measurements refer to air and surface temperature, air relative humidity, wind speed and direction. The environmental conditions are described in order to underline the differences among the four faces of the monument and to explain the nature of the decay observed on the monument. The damage risk, caused by the occurrence of phenomena like freezing-thawing cycles, thermal stress and water condensation, is estimated by relating microclimatic conditions to the stone damage processes. The results are compared to the decay map and the correlation between damage and microclimate are finally discussed.  相似文献   

8.
Limestone and marble, still frequently used as building materials are especially vulnerable to the destructive effects of efflorescence. The effect of interaction between five different calcareous stones and corrosive atmospheres has been investigated. A novel technique of stone degradation analysis has been used where thin sections of fresh stone materials were exposed in a corrosion chamber under controlled conditions (temperature, relative humidity (RH), SO2 and NO2 concentration). Following 1-week’s exposure; observations of the initial crystallisation were studied by light microscopy, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The results obtained from the surface analysis clearly showed sulphation of the samples and formation of gypsum. Observations of the initial corrosion indicated differences in the location of efflorescence and its shape among and within the samples. The mineralogy, grain shape and size, mineral defects and existence of cracks and pores, all influenced the substrate’s reactivity. The most vulnerable areas and the places where the corrosion started on the calcitic stones were the triple grain junctions followed by grain boundaries, and on the dolomitic marble cracks and pores.  相似文献   

9.
Short crystallisation and deliquescence cycles of mirabilite, epsomite and gypsum are identified by using an automated monitoring system on-site. It consists of digital cameras and RH/T sensors which are computer-controlled and connected to the Internet. Digital images are processed to form a time-lapse movie, so that surface alterations are easily recognised. High resolution imaging (6 mega pixels) in combination with various lenses (12–24 mm zoom, 28–105 mm zoom, 20 mm inversed) results in a wide range of precise observation from 7 to 500 mm width of image. That is essential for discriminating phase transitions of single crystals at the same time as monitoring the evolution of the efflorescence as a whole. Crystallisation-deliquescence cycles are induced by small temperature and humidity variations. Mirabilite and epsomite undergo phase changes from crystallisation to deliquescence and vice versa at about 83% RH (15–20 °C). These equilibrium relative humidities are considerably reduced compared to the pure salt systems as a consequence of mixed salt solutions. Observations confirm predictions by ECOS simulation based on chemical analyses of water extracts from the site. Dehydration of mirabilite is observed when the relative humidity drops below 65% RH. Mirabilite exhibits the most pronounced and rapid phase changes in response to indoor climate variations. As an example, whisker crystals of 1–3 mm length grow within one up to some days. Epsomite responds fainter and slower. Crystallisation of gypsum is distinguished by the growth of new crystals on the stone surface. They have a size of about 10 μ – which is close to the image resolution – when they appear on the image. Crystallisation is associated with an increased granular disaggregation of the stone surface. Rhythmical crystallisation of gypsum appears to correlate with small relative humidity variations of ±2–5% within a band from 65 to 75% RH in the room. However, this needs to be clarified in detail.  相似文献   

10.
In a parallel study, it has been shown by comparison of successive TV-holography campaigns that murals in the convent of Müstair (Switzerland) have progressively detached from their substrate over a time interval of 5 years (J Cult Herit 2009). Here, we focus on the dynamics of the ongoing detachment processes. In order to regularly measure small surface displacements in situ over a long duration of several years, a new method that we call Mirror Micrometry (MM) has been designed and implemented. This method monitors the reflection of a light beam by a mirror that is mounted to the surface of interest for the duration of the experiment. The mirror is designed to rotate about a pivot as small displacements in the detaching surface occur, thus deflecting the reflected light beam. Measurements over more than three years in the Convent Church and in the Holy Cross Chapel reveal various types of surface displacement perpendicular to the wall surface. These are correlated with relative humidity (RH) changes in the room climate. Reversible short-term variations of approximately ±5–10 μm occur with periods of one to several weeks and relate primarily to weather changes. Reversible long-term variations of ±5–10 μm correspond to averaged seasonal humidity changes. Irregular and irreversible movements in increments of 20–30 μm record very localised progressive detachment steps. A semi-quantitative correlation of approximately 1 μm surface displacement per 1% RH change is calculated. Based on the fact that nearby measuring points can simultaneously move in opposite directions, a geometric model is drawn to explain deformation by hygric swelling and shrinking of different shapes of detached layers.  相似文献   

11.
The impact of electric overhead radiant heaters on the microclimate, air flows, transport and deposition of suspended particulate matter (SPM) was monitored between March 2004 and March 2005 in the historic churches of Saint Michael Archangel in Szalowa and Saint Catherine in Cracow (Poland). The measurements show that although irradiation at the floor level increases temperature and reduces relative humidity in the interior of the church, the effect out of the heated zone and for the surfaces sheltered from irradiation is very limited, i.e. their extent is comparable with natural fluctuations inherent to the local climate of the church. The radiant heaters proved to generate little convectional flow of the air. Therefore, the heating system was not found to increase the concentration of SPM indoors; in particular, no re-suspension of particles already present in the church was observed. This work has demonstrated that the overhead radiant heaters are capable of providing localised heat to the areas where people congregate without adversely affecting painted walls and the works of arts displayed in churches. Care, however, should be taken that sensitive works of art are not exposed to the direct infrared radiation.  相似文献   

12.
Durability is one of the most important engineering properties of cultural heritage monuments. For the purpose of the preservation of structures for future generations, the causes of damage should be determined for the proper choice of type and location of strengthening. The condition of the foundation is difficult to determine without an extensive investigation which is critical because most often the cause of damage is found in such foundations. Geotechnical investigation techniques require the damage and destruction of a building's surroundings or the damage of a foundation with a boring device. Non-destructive methods, such as geophysical methods, are less reliable and the results of such investigations must be combined with the results of subsurface exploration. This paper is a presentation of results achieved through the monitoring of the activity of a number of joints on the Cathedral of St. Lawrence in Trogir, Croatia, which is a cultural heritage monument protected by UNESCO. Excavations for the purpose of flagging replacement in the zone around the east frontage were made in 1979. A probe beneath the main apse uncovered a water cistern where the connection between the mid and north apses is located, and instead of a staggered foundation, a wall with a depth of more than 2.2 m beneath the flagging was discovered. With respect to the given that churches were built on existing ones, it is possible to assume that this is a wall of the late-antiquity church described by Constantin Porfirogenet in the 10th century, built on and later adapted to the foundation for the new structure. The displacement in time of the construction elements of the cathedral were measured and recorded using non-destructive methods. Fissure displacement behaviour, air temperature and air humidity were monitored. The monitoring of the air humidity did not lead to any useful conclusion, so it was quickly dismissed. Observations of data were performed during two periods with an interruption between the two caused by insufficient monetary resources. Data from almost 8 years of continuous measuring are available. The aim of this paper is to present the data of the measured fissure displacements which were correlated with air temperature changes and mathematical models which were based on statistical analysis. Correlation coefficients show that the analysed fissures react to the air temperature changes with different intensities. The obtained data lead to the conclusion that the causes of the structural damage are not found within a displacement or failure of the foundations. Instead, the causes of the damage were found in other parts of the structure.  相似文献   

13.
Salt crystallization in porous materials constitutes one of the most frequent causes of decay of buildings in a wide range of environments. Up to now no definitive solution exists to limit salt crystallization damage, unless of removing either the salt or the moisture. The possibility of making the process of salt crystallization less harmful by means of crystallization inhibitors has only recently been considered. Crystallization inhibitors are known to delay nucleation and to modify the growth rate of the crystals in bulk solution, but their possible application for the prevention of salt decay in porous material is still controversial.The present paper reports a series of systematic investigations performed on three different materials (a limestone, a sandstone and a brick) contaminated with two types of salt (sodium chloride and sodium sulphate) and two types of inhibitors (sodium-ferrocyanide and diethylenetriaminepentakis methylphosphonic acid). Drying experiments have been performed to study the effect of the inhibitors on the salt solution transport. Accelerated crystallization experiments have investigated the possible consequences of the application of the inhibitor on salt crystallization damage (quantified as material loss).Environmental Scanning Electron Microscope (ESEM) has been used to study how the presence of inhibitors affects the crystallization morphology of salt in the material.The results show that the effect of the inhibitor strongly depends on the type of substrate. NaFeC, when applied on NaCl contaminated limestone and brick was able to enhance the drying and to favour the appearance of efflorescences, whereas the effect on the sandstone was very limited. DTPMP enhanced the drying of Na2SO4 laden sandstone, but had no influence on the drying of both brick and limestone. These different have been attributed to the properties of the materials, in particular pore size distribution and composition.The effects of the inhibitor on salt crystallization damage were less evident: no differences in surface damage, quantified as material loss, were observed between specimens with and without inhibitor.  相似文献   

14.
The utilization of laser light to produce fine and selective cleaning of superficial deposits and encrustation from stones was originally proposed more than 20 years ago by John Asmus who performed pioneering trials of laser cleaning on stone façades in Venice, Cremona and Padua. The opportunity to collect stone samples from these sites allowed us to carry out an original study aimed at evaluating the conservation state of stone surfaces cleaned 10–20 years ago by means of three different techniques: Nd:YAG laser radiation, micron sandblasting and chemical pads. Samples of various stone types, as Istria limestone, Botticino limestone and Nanto sandstone were collected and examined by means of optical and SEM microscopy, FT/IR, and EDAX analyses. The results provided preliminary indications that the state of conservation of stone surfaces previously subjected to laser cleaning is generally better in comparison with those which concurrently underwent mechanical and chemical cleaning.  相似文献   

15.
The chemical composition of 11 glass panes originating from two 13th century non-figurative windows were analyzed by means of Scanning Electron Microscopy–Energy Dispersive X-ray system (SEM-EDX). The windows were discovered in the back-wall of the triforium during the restoration of the choir of the cathedral St. Michael and St. Gudule in Brussels (Belgium). In order to determine if these windows were fabricated with glass of different origin or not, the compositional difference between the panes were compared with the variation in composition as a result of the following causes: (1) compositional fluctuation between panes cut from the same sheet of glass, (2) compositional fluctuation caused when panes are cut from different sheets that were made with the same batch, (3) compositional fluctuation caused when the glass is made from different batches at the same production center, and (4) compositional fluctuation as a result of glass produced at different fabrication centers.  相似文献   

16.
A life-size whitish marble statue of a “Virgin with Child” has been recently rediscovered in the St. Rosario church located in Ottaviano, a small town near Naples (southern Italy). This artwork shows stylistic features of the Tuscan-Roman school of the 16th century, and is framed in an intriguing historical context. Historical documents testify that the sculpture was a property of the cadet branch of noble Tuscan family of the Medici, the Medici of Ottaviano. A multianalytical approach has been used to try to indicate the supply area of the white marble of the studied sculpture. Considering the whole mineralogical, petrographic and geochemical data, the source rock can be possibly limited to the main classical white marbles of the Mediterranean district, as the classical marble of Aphrodisias. A reuse practice of a former artwork can be also hypothesized.  相似文献   

17.
Two multivariate statistical tools – principal components analysis and cluster analysis – were applied to aid in the interpretation of the historical development of St. John the Baptist's church (?i?e, Slovenia). With these methods it was possible to distinguish between the types of mortar used in the Romanesque and Gothic time periods. The investigated structure is a ruin with poorly preserved fragments of historical mortars, so tracing the individual stages of its construction proved to be a demanding task. Its chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS) and the results of the content of various oxides were statistically evaluated to interpret the age of the southern wall of the church.  相似文献   

18.
The scientific approach to the restoration and monitoring of mural paintings, at S. Girolamo Chapel – SS. Annunziata Church in Florence, is reported as a fruitful example of the synergic collaboration between restorers and scientists in the planning and development of conservative interventions. Before restoration, the painting technique and the state of preservation of the pictorial cycle have been investigated firstly by close examination of the painted surfaces and then by optical and/or SEM-EDS microscopy and μFT-IR spectroscopy on appropriately selected samples. In particular, the original constituent materials and those belonging to subsequent restorations were characterized together with those originating from decay processes. In this mural painting cycle, a peculiar “fresco” technique has been used although an auxiliary binder for pigment distemper has been also employed. The use of this technique, sometimes in an improper way together with uncorrected restoration interventions, are the main responsible of the unsatisfactory state of conservation of many painted areas. Preliminary conservation trials and scientific studies were carried out to design the most convenient restoration intervention and to verify the correctness and non-invasive of the necessary operations. Special attention was devoted to cleaning procedures, continuously monitored by a physico-chemical methodology, mainly based on microinvasive, microscopic and spectroscopic investigations, to evaluate the efficiency, advantages and drawbacks of the proposed cleaning procedures and define the most appropriate ones. Finally, specific decay markers have been recognized, by a comparison of the results obtained from the detached samples with those deriving from artificially aged models, to be used for a correct future monitoring and maintenance of the wall paintings.  相似文献   

19.
Monumental stone decay is a consequence of the weathering action of physical, chemical and biological factors, which induce a progressive increase in porosity. To cope this degradation, bacterial calcium carbonate mineralization has been proposed as a tool for the conservation of monumental calcareous stones. The advantage of this kind of treatment is to obtain a mineral product similar to the stone substrate, mimicking the natural process responsible for stone formation. In this work, the possibility to induce CaCO3 mineralization by a bacteria-mediated system in absence of viable cells was investigated and tested on stone. Our results showed that Bacillus subtilis dead cells as wells as its bacterial cell wall fraction (BCF) can act as calcite crystallization nuclei in solution. BCF consolidating capability was further tested in laboratory on slab stones, and in situ on the Angera Church, a valuable 6th century monumental site. New crystals formation was observed inside pores and significant decrease in water absorption (up to 16.7%) in BCF treated samples. A little cohesion increase was observed in the treated area of the Angera Church, showing the potential of this application, even though further improvements are needed.  相似文献   

20.
Piperno, a Late Quaternary magmatic rock cropping out on the eastern side of the Campi Flegrei (Italy), is probably the most important building stone of Naples, used over a time-span from at least the Roman age until the beginning of the 20th century. Despite its wide diffusion in the monumental architecture of Naples, very little is known about this rock, as regards its technical features, as well as the geological aspects. This paper aims at providing a first overall contribution towards a rediscovery of this long-time-used material, in view of careful restoration works, which nowadays at Naples only take into account the proper geological features of the stone in a few peculiar cases. Thus, it seems of extreme importance to understand the basic parameters of Piperno and, above all, its response to weathering agents. Main mineralogical, petrographical and engineering–geological properties are presented here for the first time, with specific reference to two sampling areas, located at Pianura and Soccavo, in the western sector of the Neapolitan urban area. As far as many of its physico–mechanical features are concerned, Piperno extends over a wide range of values, which allow different varieties of the rock to be identified. This preliminary result is seemingly in accordance with data from old historical literature, which stated the existence of six horizons in the Piperno formation.  相似文献   

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