Excimer laser removal of beeswax from galician granite monuments

The paper presents the use of laser radiation for cleaning of beeswax treated granite stone. In the early sixties, prestigious restorers decided to apply molten beeswax on the granite surface of valuable monuments with the aim of preventing the erosive action of atmospheric agents. An interesting example of this treatment is the Renaissance Frieze in the Cloister of the Cathedral of Santiago de Compostela in Galicia (Northwest Spain). With time, salt accumulation beneath the beeswax layer has caused an intense surface disintegration of granite. Conventional cleaning methods can destroy sculptured details of these emblematic monuments. For this reason, excimer laser cleaning has been chosen as a promising non contact, selective and environmentally friendly cleaning technique to be studied.The cleaning tests have been carried out using an excimer laser (ArF, 193 nm), with fluences between 0.5 and 2 J cm⁻² pulse⁻¹ and a spot area of 0.025 cm². Samples representing beeswax films over Roan granite have been irradiated and their degree of cleaning has been studied as a function of the number of pulses and the laser fluence.Cleaning efficiency has been evaluated by FT-Raman Spectroscopy, allowing to establish the beeswax ablation threshold and the ablation rate.Excimer laser cleaning allows a progressive and controlled removal of a few tenths of micrometers of beeswax per pulse without damaging the underlying granite stone.     

Validation of non-destructive characterization of the structure and seismic damage propagation of plaster and texture in multi-leaf stone masonry walls of cultural-artistic value

Assessment of multi-leaf stone masonry in earthquake-prone areas is mostly related to the evaluation of its texture, morphology, leaf detachment and structural cracking due to previous seismic activity, as well as disintegration due to material deterioration. For the plastered masonry with heritage or artistic value (paintings, frescoes etc.), both the type of structure and the extent of damage should be characterized with minimal interference to the structure, which could be overcome solely by non-destructive testing (NDT). However, due to the complexity of plastered multi-leaf masonry structure, the performance of well-known NDT methods could be significantly worsened. Therefore, as a prerequisite for applying NDT on multi-leaf stone masonry in practice, a validation process should be carried out. In this study, complementary ground penetrating radar (GPR) and infrared (IR) thermography measurements on plastered laboratory three-leaf stone masonry walls were performed. Apart from assessing the wall texture and morphology with the type of connection between the leaves, detection of gradual plaster delamination and crack propagation while subjecting the walls to an in-plane cyclic shear test was taken into account. The results showed that GPR could successfully visualize header stones passing through the whole depth of the specimen. The masonry texture behind the plaster could be well resolved by both methods, although GPR near-field effects worsened its localisation. For the detection of plaster delamination, IR thermography outperformed GPR by detecting delamination as small as 2 mm as well as structural crack patterns, whereas GPR only detected delamination larger than 8 mm. It was shown that the performance of both methods for defect detection could be further improved by image fusion based on unsupervised clustering methods.     

A qualitative method for combining thermal imprints to emerging weak points of ancient wall structures by passive infrared thermography – A case study

The significant number of buildings constructed in the world before the appearance of compulsory earthquake projecting norms, as well as the subsequent construction in the safe seismic zones, requires a constant re-evaluation of the strength of the structures. For example, the 2009 earthquake happened in L’Aquila city (Italy), killed about 300 people. Furthermore, many old buildings, seriously damaged, were considered as historical monuments and their importance is still critical both from a cultural standpoint and for the city itself. On the basis of the surveys carried out by the Las.e.r. Laboratory (university of L’Aquila) before and after 2009 earthquake, this paper introduces the infrared thermography (IRT) as a mean to characterize particular thermal imprints that appear on ancient facades, employing the passive thermography, discussing the infrared images collected during several years, and analyzing their relationship with all kinds of influence factors, in order to validate the effectiveness of the technique and its role in preventive diagnosis.     

Microfacies analysis and endogenic decay causes of carbonate building stones at the Asklepieion Epidaurus monuments of Peloponnessos,Greece

The carbonate building stones from the Asklepeion, Epidaurus, used to construct the monuments of Gymnasium, Tholos and Avaton can be grouped into 12 microfacies types, according to their microfacies characteristics such as the type of groundmass, the different kinds of particles, the facies-diagnostic fossils, the depositional and solution textures. Two of them, oocalcarenite (MF type I) and biocalcarenite (MF type II) belong to the marine Plio-Pleistocene carbonate sediments from Korinthos (ancient quarries in Kechries) and the northern part of the island of Aegina, respectively. Most of them, calcrete (MF type III), red biomicrites (MF type IV and V), oolitic grainstone (MF type VI), bio-grainstone (MF type VII), boundstone (MF type VIII), intrabreccia limestone (MF type IX), cherty biomicrite (MF type X) belong to the sedimentary carbonate formations of Mesozoic age of the adjacent areas in Argolis peninsula. The black lime-biomicrite (MF type XI) comes from a more distant sedimentary lithological formation, most probably from Dervenakia area (Tripolis zone). Finally, one belongs to the metamorphic carbonates (marbles of Naxos?). The endogenic decay causes are controlled by both sedimentary and diagenetic processes reflected in the microfacies type. So, the main endogenic factors of the oocalcarenite and biocalcarenite facies, which were used for the upper architectural members, are high porosity and the quantitative–qualitative mineralogical composition of the insoluble residue, which is mainly composed of swelling clay minerals (smectites). The calcrete facies, which was used in the foundations of all monuments, shows the heaviest decay problems which are related to the high structural irregularities, the high porosity and the quantitative–qualitative mineralogical composition of the non-carbonate minerals. The other facies appear with a weaker degree of decay whose endogenic causes are also investigated.     

Assessment of synthetic polymeric coatings for the protection and preservation of stone monuments

The performance of five synthetic coatings for the protection of stone monuments of Hellenistic and Byzantine period has been evaluated. The selected coatings included four commercially available siloxane-, siloxane/acrylic- and perfluoroether-based compositions, as well as a new composition based on newly synthesized fluoro-organosilane. The coatings were applied onto petrologically different stone substrates, such as marble, travertine, sandstone and a newly baked brick compatible with Roman period bricks, used for the restoration processes in Galerius Palace, Thessaloniki, Greece. The coatings' protective efficiency was investigated by measurement of water–stone contact angles, water vapor permeability, and water absorption by capillarity. The optical properties of the applied coatings were also investigated and they were also ranked with regard to their optical characteristics.     

A color image segmentation method as used in the study of ancient monument decay

In the cultural heritage area, it is of fundamental importance to characterize and classify the conservation state of the materials constituting ancient monuments, in order to study and monitor their decay. Generally, the decay diagnosis is provided by “naked eye” analysis done by expert scientists “walking around” the artifact and recording the conservation state of each individual element they observe. In this paper, a color image segmentation approach, based on histogram threshold and edge detection techniques is presented, to extract degradation regions, characterized by holes or cavities, from color images of stone-materials. The goal is to provide an aid to the decay diagnosis by segmenting degraded regions from color images, computing quantitative data, such as the area and perimeter of the extracted zones, and processing qualitative information, such as various levels of depth detected into the same zones. Since color is a powerful tool in the distinction between objects, a segmentation technique based on color, instead of intensity only, has been used to provide a clearer discrimination between regions. The study case concerns the impressive remains of the Roman Theatre in the city of Aosta (Italy). In particular, we have processed and analyzed some color images of the theatre puddingstones, acquired by a camera.     

Fluorescence lidar technique for the remote sensing of stone monuments

This paper presents the first investigation on the remote sensing of stone monuments by fluorescence lidar. The advantages of this technique are manifold and can lead to a fast, extensive and inexpensive control of the stone cultural heritage. The experiments were carried out in both the laboratory and the field, and include the survey of stones coming from different quarries, of epilithic photosynthetic biodeteriogens and of a monument, the Parma Baptistery. The results constitute a first step towards a non-destructive spectral analysis of stone monument surfaces.     

Environmental conditions controlling the chemical weathering of the Madara Horseman monument,NE Bulgaria

The conditions that led to the deterioration of the Madara Horseman sculpture, a relief carved in a sandy limestone cliff in north-east Bulgaria, were studied, with most emphasis on the chemical weathering at the stone–atmosphere interface. Total deposition sampled close to the monument contains high concentrations of NH₄⁺ and K⁺, which shows the influence of the dense vegetation in the area, and Ca²⁺, which reflects the cliffˈs weathering products. Ca²⁺ is also one of the most important constituents (next to aluminosilicates) of the atmospheric particulate collected at the monument. S-rich particles are the most abundant particles in the size range < 0.5 μm. High amounts of biogenic particles (K-P-S-rich) were found, especially for particles < 1.0 μm. The chemical, mineralogical and petrographic characteristics of the stratum that holds the monument were studied down to a depth of 20 cm. Two distinctive processes are active at the stone–atmosphere interface. Firstly, a weathering crust (ca. 2 mm thickness), consisting mainly of calcite and gypsum and enriched with Cl^–, K⁺ and NO₃^–, is formed in the rain-sheltered areas of the monument. Secondly, karstic dissolution in the interior of the rock substrate leads to the formation of a hard carbonate crust at the surface of the sculpture. This natural surface hardening leads to a state of ‘auto-conservationˈ of the monument. The atmospheric composition seems to have only a limited influence on the deterioration of the Madara Horseman. Far more important are the micro-climatic conditions and the action of lichens.     

长三角一体化背景下开发区发展研究--以苏州工业园区为例

长三角地区是我国开发区发展的密集区。作为微观的区域发展模式,开发区的发展历程研究对于开发区自身转型升级和健康发展、区域一体化高质量发展具有重要的启示意义。以苏州工业园区为例,通过经济社会发展定量化评价,探究开发区发展的规律性特征,将园区发展划分为三个阶段:①经济社会波动增长阶段(2004年以前);②经济社会同步提升阶段(2005-2011年);③社会持续提升、经济稳定阶段(2012年以后),认为苏州工业园区经济社会健康发展得益于根据外部政策要求和自身发展阶段坚持了有力的空间规划引导、保持了经济社会发展的均衡性,并通过不断调整空间规划和策略实现了区域协调融合发展。     

Contact sponge method: Performance of a promising tool for measuring the initial water absorption

Porous limestone and mortar are able to absorb large quantities of water. This phenomenon will accelerate the deterioration of the material. In such cases, the material might be treated with a hydrophobic product, which creates a superficial layer that hampers the penetration of water. In order to decide if such a treatment should be applied or not, the water absorbing behaviour of the material should be measured. With the same measuring technique the efficiency of the hydrophobic barrier can be evaluated. Moreover, it allows the monitoring of such barriers as a function of time. At the same time, the water absorption of porous stone material is an indication of the degree of deterioration and its sensitivity to future deterioration. Up to now, two different measuring techniques exist, but one can only be used in laboratory and the other, which can be operated in laboratory as well as in situ, is not always reliable for in situ analyses. This article proposes an alternative method: the contact sponge method. This recently developed method was tested on non-treated porous stone materials in a laboratory environment in order to evaluate its performance in comparison with the two existing methods.     

How wet are these walls? Testing a novel technique for measuring moisture in ruined walls

Moisture in walls provides a key control on decay processes, but has proved difficult to measure. As part of a larger study investigating the ability of soft wall capping (soil and vegetation) to help conserve ruined monuments we have investigated moisture contents of walls at two ruined abbeys. Two methods of moisture measurement were used, i.e. a novel adaptation of 2D electrical resistivity surveys and the well-established wooden dowel method. Medical ECG electrodes were utilised to provide a completely non-destructive resistivity measurement. At Hailes Abbey wooden dowel and 2D resistivity measurements were made of soft capped vs. uncapped wall sections. The wooden dowels showed drier conditions in the core of the capped sections, although the resistivity surveys were influenced by a different stone structure in the wall core. At Byland Abbey, resistivity surveys indicated drier stone blocks and wetter mortar in the near-surface zone, and illustrated the success of the soft-capping technique in reducing water contents in the core of the wall in comparison with hard-capping with mortar. The 2D resistivity technique is shown to be a useful and fast non-destructive technique with the capacity to provide good spatial and temporal resolution information on moisture distribution in walls.     

Damage on hydraulic mortars: the Venice Arsenal

Very few scientific studies have been performed so far on ancient and modern hydraulic mortars. The effects of atmospheric multi-pollutants on hydraulic mortars used in monuments and historic buildings in urban areas, especially those linked to dry and wet carbon and sulphur deposition, remain in need of thorough investigation. In the literature, studies on damage typology identification, composition and origin and relative quantitative data are both scarce and rather poor in quality. While the sulphate source from marine spray deposition and water capillary rising are known, atmospheric sulphur effects on mortars still require elucidation. Ancient and modern hydraulic mortars have been collected from the Arsenal of Venice. The original material characterisation and the evaluation of the surface damage due to atmospheric pollution are presented along with a comparison of the data obtained for the cement and cocciopesto mortars.     

Protective effect of endolithic fungal hyphae on oolitic limestone buildings

This study presents characterizations of weathering forms of the same oolitic limestone from four quarries and eight monuments exposed on various environmental conditions focusing on the waterproofing effect of endolithic organic matter. Patinas were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX), capillarity coefficient through weathered and unweathered sides, gypsum content and porous network morphology by epoxy resin molding. Study of weathering forms on old quarries indicates that lichens colonization (Verrucaria nigrescens and Caloplaca aurantia) can fill the superficial porous network with a dense network of lichenised fungal hyphae. Capillary coefficient measurement on natural and calcinated samples showed that endolithic organic matter can waterproof the stone and could act as a sulfate contamination barrier. Similar endolithic organic layer due to ancient lichens growth are found on some antique monuments of the Nîmes downtown and could explain their well-preserved state, unlike decayed 19th century churches that were never colonized by lichens.     

An integrated and automated segmentation approach to deteriorated regions recognition on 3D reality-based models of cultural heritage artifacts

In the field of Cultural Heritage, image analysis represents an indispensable practice for restorers to collect information about the state of preservation of monuments and artifacts and plan restoration interventions. In addition, during the last two decades, the wide spread of remote sensing technologies and the possibility to build 3D reality-based models of artifacts allow the extension of image analysis to 3D environments. In this context, the purpose of this contribution is to show the results of investigations held in order to provide a methodology for the automatic detection of deteriorated areas within architectures and artifacts using colour images as a field of examination. Using both 2D and 3D segmentation approaches, our methodology aims at speeding and efficiently performing the automatic detection of deteriorated zones within Cultural Heritage and therefore segment 3D digital models acquired using different survey technologies. Within our investigations, we selected case studies concerning recurrent deteriorations, such as, for example, detachments, cracks and chromatic alterations; we run them both to manual and to automatic recognition and selection tests, in order to compare the results obtained using these approaches and evaluate the reliability of the automatic one. Results comparison included computational and user time, quantification of the deteriorated area error between manual and automatically detected zones. Additional parameters characterizing the specific type of deteriorations were also computed for each case study. Comparison between the automatic and the manual procedure showed that the automatic detection is faster and reliable in all our selected case studies, with evident improvements in the efficient evaluation of the entity and extension of deteriorated areas on 3D geometry.     

Decay regions segmentation from color images of ancient monuments using fast marching method

This work faces the problem of detecting decay zones from color images of stone materials. In Cultural Heritage, the extraction of degradation regions from images of ancient monuments represents an important step forward in studying and analyzing the state of preservation of historical buildings. Generally the decay diagnosis is provided by “naked eye” analysis done by expert scientists “walking around” the artifact and recording the conservation state of each individual element they observe. In addition to this kind of investigation, the application of an image segmentation strategy to color images of stony materials can be used in order to extract regions characterized by a visible chromatic alteration, changes in color, for example, as oxidation or concretion. This paper features a color image segmentation approach founded on the fast marching numerical method. We have applied this technique for its possibility to work locally, that is, only the contour of the region under study is processed. In addition to this method, we present a global approach, that is, the possibility to extract decay regions from the entire image; these regions are spatially disconnected but with similar colorimeter value. The main aim of the present work is to provide a tool that helps the expert to contour the degraded regions. In this sense even if the results of the proposed procedure depend on the expert evaluation, the approach can be a contribution to improve the efficiency of the boundary detection process. The study case concerns the impressive remains of the Roman Theatre in the city of Aosta (Italy). In the image segmentation process the color space L*a*b* is utilized.     

The origin of syngenite in black crusts on the limestone monument King's Gate (Belgrade Fortress,Serbia) – the role of agriculture fertiliser

Black crusts formed on limestone built into the King's Gate represent the most important process in stone deterioration that is occurring in this part of the monumental complex of the Belgrade Fortress (Serbia). Of special importance is the association of salts (namely gypsum and syngenite). Syngenite is a common secondary deposit on granite monuments and on medieval stained glass (i.e., on K-containing materials). However, its appearance over calcareous substrates is not apparent, particularly in cases where cement mortar was not used for bounding. The origins of the potassium and sulphate ions required for syngenite formation are related to meteoritic water, which penetrates the soil above the arch of King's Gate. Water dissolves some soil components and becomes enriched with various ions before coming into contact with the limestone blocks. Enriched water contains two times more K⁺ and SO₄^2? ions than pristine meteoritic water does. The source of the required ions is potassium-sulphate that is present in agricultural fertilisers that are used above the monument. The proposed mechanism for syngenite formation was additionally supported with laboratory experiment. The results of X-ray diffractometry and SEM-EDS analyses of limestone treated with potassium-sulphate solution and sulphuric acid suggest the possibility that the syngenite was formed over calcite:CaCO₃ + K₂SO₄ + H₂SO₄ → K₂Ca(SO₄)₂ H₂O + CO₂↑However, the complex mechanisms of gypsum and syngenite formation under natural conditions (variable concentration of potassium and sulphate ions, intermediates phases, temperature changes, humidity, the amount of disposable water etc.) do not exclude the possibility of syngenite formation over gypsum.     

First results of using combined mass and temperature measurements to study the water flow at the rock–atmosphere interface

The preservation of historical monuments requires both a detailed understanding of water circulation inside construction materials, and a deep comprehension of the associated physical and chemical effects on building structure. Combining mass and temperature measurements may be a new powerful tool to achieve this purpose, as first results obtained on a wall of the Saint-Gatien cathedral in Tours, France, indicate. The proposed method has been evaluated with dedicated experiments in a climatic chamber, regulated in both temperature and humidity, using three types of stones: Tours tuffeau, Baumberg limy sandstone, and Rüthen sandstone. Climatic chamber data indicate that temperature gradients between rock surface and atmosphere provide a meaningful and practical estimate of the water flow, which controls the heat exchange between rock and atmosphere because of the high enthalpy of vaporisation of water. Continuous measurements of the mass of a sample confirm this assumption and allow the calibration of temperature data with respect to water flow estimations. Temperature gradients between points on the stone surface are also dominated by changes in the water flux, and they provide a sensitive estimate of local variations in the heat and water transport properties of non-saturated stones. Combined mass and temperature measurements therefore appear as a promising method to estimate in situ the global and local water flow between the rock and the atmosphere and thus to diagnose the state of stone degradation, or to estimate quantitatively the efficiency of treatment processes, both in the field and in the laboratory.     

Efflorescence on thin sections of calcareous stones

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.