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1.
Consolidants based on tetraethoxysilane (TEOS) have been widely used for the consolidation of decaying stone heritages. These products polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developed capillary force, which is typical for TEOS-based consolidants. We have prepared new consolidants TEOS-based consolidants containing flexible (3-glycidoxypropyl) trimethoxysilane (GPTMS) and silica nanoparticles in order to reduce capillary force development during gel drying, and have characterized them for the application of stone consolidants. Different sizes of silica nanoparticles were used, which were smaller than the pore size of the tested stone. The properties of the TEOS/GPTMS/nanoparticle composite solution were compared with those of the commercial products Wacker OH and Unil sandsteinfestiger OH 1:1. The gelation time was similar to that of commercial consolidants, and the TEOS/GPTMS/nanoparticle solution was stable over a period of up to six months. The contact angle of the surface increased with the addition of the nanoparticle, as well as with the addition the GPTMS, which is higher than that of commercial Wacker OH. The addition of a nanoparticle, as well as GPTMS having flexible segment, provided a crack-free material, while the gels obtained from the commercial consolidants exhibited cracking.  相似文献   

2.
For conservation of the built cultural heritage, the application of conservation products like consolidants or water repellents is often suggested. Their impregnation depth is a key factor for the assessment of the treatment efficiency. It will vary depending on the internal structure of the stone material and the properties of the conservation products. In this study a porous bioclastic limestone from Maastricht (the Netherlands) and a porous sandstone of Bray (Belgium) were selected for treatment with either ethylsilicate-based consolidant products or siloxane-based water repellents. We explore the potential of neutron radiography to visualize the conservation products after polymerization, since previous experiments already proved their detectability before polymerization. Additionally, water absorption by capillarity was monitored inside the samples. The experiments in this study illustrate that the ethylsilicate-based consolidants remained visible for neutrons even after the polymerization process, while the siloxane-based water repellents can only clearly be distinguished in the stone as long as they contain a certain amount of solvent. The study proves that neutron radiography can provide important additional information for the research in the built cultural heritage domain, especially as it allows to successfully visualize the impregnation depth of silicate-based consolidants inside natural building stones.  相似文献   

3.
Stone consolidation is one of the major restoration treatments used for historical monuments preservation. A natural stone is a complicated heterogeneous porous system making the process of consolidation dependent on many variables. In practical restoration aims, for a given stone type, the selection of a suitable consolidant and consolidation conditions therefore remains a complex issue. The impregnation depth is a key factor for the assessment of the treatment efficiency. The combination of state-of-the-art hybrid pixel semiconductor detectors with newly available micro-focus X-ray sources makes possible to apply X-ray radiography, an ideal non-destructive tool, for penetration depth monitoring. In this study, high-resolution X-ray radiography is used for monitoring the penetration depth of organosilicon consolidants in the Opuka stone. The penetration depth has been evaluated in relation to the time of consolidation, stone porosity and consolidation mixtures properties. The exact influence of the X-ray contrast agent on the consolidation depth has been investigated as well. The information obtained provides supplementary knowledge on the suitability of investigated products for the treatment of this type of stone. In our study, the capabilities of X-ray radiography have been demonstrated on X-ray radiography simple projections, high-resolution computed tomography (CT) as well as on the dynamic processes monitoring. The results thus can serve also as an instrumental and methodological example applicable for consolidation monitoring of other stone types.  相似文献   

4.
Stone consolidation: The role of treatment procedures   总被引：3，自引：0，他引：3  
Four types of carbonate stones and three consolidation products were used in a systematic study to assess the influence of the application procedures on the amount of product applied, as a primary step to evaluate consolidation treatments. Microdrilling, ultrasonic velocity and flexural resistance were used as performance indicators. The amount of product of a specific treatment and its action depend on the application procedures, both when the treatments are carried out in the laboratory and on site. The results are expected to contribute to the standardisation of testing protocols on stone consolidation.  相似文献   

5.
Epoxy resins, widely used in conservation, still remain controversial materials. Considering some of the drawbacks that currently limit the application of epoxy consolidants, we present the application of the cationic ring opening polymerization as a novel method to cure the epoxy monomer in the restoration field. The cationic polymerization was carried out through a redox system based on the reduction of the iodonium salt in the presence of ascorbic acid catalyzed by a copper salt. The use of this initiator system for carrying out a suitable consolidant for lime plaster is considered. First, the film properties of the cured films were investigated. Then, the formulation was applied on a sample of plaster and its compatibility was verified. Its effectiveness as a consolidant product is explored through the evaluation of chromatic changes, mechanical strength, morphology of the re-aggregated material, and changes of the surface properties.  相似文献   

6.
When timber elements in heritage buildings are moderately degraded by fungi and assuming underlying moisture problems have been solved, two actions can be taken: i) use a biocide to stop fungal activity; ii) consolidate the degraded elements so that the timber keeps on fulfilling its structural and decorative functions. The aim of this work is to investigate the mechanical performance of maritime pine wood degraded by fungi after being treated with a biocide followed by impregnation with a polymer product. Three commercially available products were used: a boron water-based biocide, an acrylic consolidant and an epoxy-based consolidant. Treated and consolidated specimens were subjected to mechanical tests: axial compression test (NP 618), static surface hardness (ISO 3350) and bending test (NP 619). Sets of replicates were subjected to an evaporation ageing test (EN 73) after application of the products and also tested for mechanical behaviour. An increase in mechanical strength was observed for both consolidants with no significant influence from the previous use of biocide product. The specimens subjected to ageing showed a slightly better general mechanical performance.  相似文献   

7.
An epoxy coating modified by PDMS hydroxyl terminated is presented in this paper in order to evaluate its potential use as a protective of a stone surface. With a view to its use in restoration sites, visible and long-wavelength photoinitiated cationic polymerization is proposed here. The system investigated is based on a crosslinking mechanism which shows remarkable advantages for stone protection, such as the low toxicity of the products and facility of mixture preparation. Furthermore, the visible light exploitation represents the most important advantage, because it is easy to apply in a restoration site, with or without irradiation instruments. Besides coating characterization through FT-IR, DMTA analyses and contact angle measurement on glass slides, analyses were also carried out on coated plaster samples. These analyses were performed in order to evaluate the effectiveness of the protective, in relationship to hydrophobicity (contact angle measurement, capillary water absorption) and morphology surface changing (SE/SEM observations, colorimetric measurements) before and after polymer application and UV aging test of coated samples. The overall characterization makes it possible to consider it a suitable coating for stone protection.  相似文献   

8.
The recent development of a new drilling machine in the framework of the EU project HARDROCK brought some interesting perspectives for the characterisation of decay profiles, for tracing old consolidating treatments and for evaluating new consolidants. The equipment executes a drill hole, typically 5 mm in diameter, down to 5 cm, under precisely defined and controlled drilling conditions. The output is a graph of force versus depth. The instrument can be transported and operated in situ. The operator defines the drilling rotation speed and the advancing rate and the instrument registers the force required for executing the hole under those strictly defined conditions. This paper presents some data taken from a laboratory study on consolidants which demonstrate that the equipment has a very high discriminating power for detecting the presence of consolidants. Clear differences among some typical consolidants were detected, both in the strength increase and in the penetration depth. They also show that the average drilling forces present a fairly good correlation with bending strength, in spite of the fact that full consolidation of the tested specimens was not possible with all consolidants. The in situ study of Porta Especiosa has shown that the instrument was able to identify the presence of decay events at several depths, in a way that no other known method can do. The identification of the presence of old treatments was demonstrated with total guarantee.  相似文献   

9.
Hybrid stone consolidants prepared from tetraethoxysilane (TEOS) and α,ω-hydroxyl-terminated polydimethylsiloxane (PDMS-OH) have been considered as one of the most promising approaches to improve the effectiveness of traditional alkoxysilane-based formulations. They have emerged as response to the negative reports commonly found in the literature: the resulting silica gel phase (SiO2) tends to develop fractures and fissures inside the stone as the gel shrinks during the drying stage. In this work, we employed SEM, solid-state 29Si NMR spectroscopy and compressive tests to characterize SiO2-PDMS hybrid gels. We report the morphological characteristics exhibited by gels prepared in vitro and in situ. It was found an appreciable reduction of gel fracture for hybrids prepared from 5% w/w of PDMS. As TEOS polycondenses, PDMS-OH is chemically incorporated into the gel matrix via Si-O-Si bonds. The inclusion of these elastic chains provides the necessary flexibility to resist the stress imposed by capillary pressure. Additionally, an important hydrophobic character is imparted to the stone.  相似文献   

10.
The influence of chemical treatments based on novel organic products on the consolidation of deteriorated wood by insect attack was evaluated on two hardwoods and one softwood: fir (Abies alba), beech (Fagus sylvatica) and deciduous oak (Quercus sp.). Degraded and intact specimens of the three wood species were impregnated with two different chemical treatments aimed to verify the potential synergic action of the novel products on wood. Then, the specimens were subjected to bending, compression parallel to the grain, impact, hardness and water absorption tests. Untreated specimens of the same botanical species, both degraded and non-degraded, were examined for comparison purposes. The experimental results showed a different effectiveness of the proposed chemical treatments to improve the mechanical and absorption properties of degraded wood. The most effective treatment was the one assuming the concurrent use of the studied novel consolidants. The species more susceptible of the enhancement in mechanical properties were fir and beech. The observed differentiations were most likely caused by the different structure of the botanical species considered, leading to a consequent different product penetration in the wood structure. The dimensional stability in terms of water repellent and antiswelling efficiency, after a three-month immersion in deionized water, was found to improve in all the treated wood specimens. Overall, experimental results showed that the impact of the chemical treatments was higher on degraded samples than on intact ones.  相似文献   

11.
Stained glass windows belong to the most precious pieces of art in many European countries. Examples of heavily endangered paint on glass are reported in the literature and mainly related to condensation effects and air pollution, as stained glass windows preferably remain in their original architectural surrounding. Several surface coatings and paint treatments have been proposed to consolidate and protect degraded paint. Very often, the selection of the materials is based more on practical aspects than on scientific research. This study concerns the comparison of some traditional, modern and newly developed consolidants for the preservation of historic glass paintings. Experiments have been carried out with model painted glass samples simulating weathering phenomena of originals. Traditional materials like Paraloid B72, modern ones like SZA (proposed by the Fraunhofer-Institut für Silicatforschung, ISC), and three new consolidants prepared by the sol–gel method and based on different hybrid organic–inorganic alkyl-alkoxysilane systems have been considered. The adhesion, penetration, stability, hydrophobicity, mechanical and chemical resistance are properties and requirements tested to prove their effectiveness and range of use. The three new materials developed in this study for the consolidation of paint on glass have the potential to offer alternatives to existing materials. Nevertheless, further research is necessary before their application in restoration workshops can be recommended. A strategic approach is requested to avoid risks for these valuable historical originals and to contribute to the long-term preservation of the paint on stained glass windows in their original sites.  相似文献   

12.
The feasibility and the effectiveness of using hydroxyapatite (HAP) formed by reacting limestone with a solution of diammonium hydrogen phosphate (DAP) in mild conditions, as a consolidant for carbonate stones were investigated. Firstly, a novel method for predamaging limestone was developed. Then, the effects of DAP solution concentration and reaction duration were evaluated to define the best treatment conditions, and the strengthening effect was evaluated on artificially damaged Indiana Limestone samples. Treated samples exhibit a significant increase in the dynamic elastic modulus and tensile strength, which is attributed to microcrack reduction and pore filling consequent to formation of calcium phosphate phases at grain boundaries, as assessed by SEM/EDS and ESEM/EBSD. Consequent to a slight reduction of coarser pores, as revealed by MIP, the sorptivity of treated samples is only slightly reduced, so that water and water vapor exchanges with the environment are not significantly blocked.  相似文献   

13.
The growing interest in the conservation of historic buildings encourages the development of water-repellent materials and methodologies to consolidate and/or protect stones. Recently, particular attention was devoted to composites of inorganic oxides nanoparticles and hybrid siloxane or silicone polymers. Here we present a study on the water repellence of a thin protective coating obtained through sol-gel process starting from Glymo and Dynasylan 40®, and loading the silicate matrix with nano-sized silica particles (Aeroxide LE1® -Degussa-Evonik). The coatings were applied to limestone, sandstone and granite samples. The silica nanoparticles have been characterized by XRD, the siloxane matrix through micro-Raman spectroscopy, while the surface morphology was examined by SEM. The efficacy of the treatments has been evaluated through static contact angle measurements and capillary water absorption. The optical appearance of the coatings was evaluated by colorimetric measurements. Nanoparticles at suitable concentration gave high values for the static contact angle (up to ∼ 150°), for all stone species even for four months exposure to atmospheric conditions. The coatings, in the water capillary absorption tests, however, behave as expected only for granite even if the long-term water direct contact reduces the hydrophobicity.  相似文献   

14.
Titanium dioxide (TiO2) can be used to realize transparent self-cleaning coatings on stone surfaces as an active and preventive protection system, limiting cleaning and maintenance actions, reducing their costs in Architectural Heritage. This self-cleaning ability is due to photo-induced hydrophilicity on treated surfaces. The aim of this investigation is to analyze this effect, since it could bring to a greater water absorption, a potential source of damage for stone surfaces. Titania sol, obtained by sol-gel and hydrothermal processes, was deposited on travertine by spray coating, in two different ways. Water absorption by capillarity, static contact angle and a specific surface water absorption analysis were assessed before and after the TiO2 treatments. The effects of deposited amount of titania on the characteristics of treated surfaces were evaluated. It was shown that there were no evident changes in the substrate reactivity without ultraviolet (UV) light exposure, while it seems that hydrophilicity due to UV light does not lead to higher water absorption, thus encouraging the use of TiO2 coatings in the field of Architectural Heritage. However, before widely applying this conservative treatment, some further researches are recommended in order to better assess its durability and sustainability.  相似文献   

15.
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.  相似文献   

16.
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   

17.
This paper aims at proposing a new calibration material for microdrilling resistance measurements. Microdrilling resistance is a microdestructive method mainly used in built heritage in order to determine the strength profile in depth. This method is suitable to detect changes in the material cohesion, either due to a different state of preservation or to the action of a consolidant. Calibration materials are often used in microdrilling measurements in order to characterise the drill bit initial value and to correct the variations existing within the initial values of a set of drill bits. Calibration materials are also useful to detect the wear effect on a drill bit due to an abrasive stone. Moreover, such materials can be used for comparing results obtained with different microdrilling machines. In this work, halite was chosen to be tested as a calibration material due to its properties, as low hardness and isotropy. Halite single crystals and halite salt stone from different provenances were tested in order to evaluate the suitability of this material to the requests of a calibration material for microdrilling resistance applications, as for instance being homogeneous, non-abrasive, sensitive and available worldwide. Experimental results show that halite from different provenances is very homogeneous, especially in the crystalline form. This form of halite is slightly more expensive than stone halite; however its costs are comparable to ARS and significantly lower than Macor (other calibration materials commonly used for microdrilling resistance measurements). Due to the advantages of halite for calibration purposes, this material should be further tested by other authors in order to validate our conclusions.  相似文献   

18.
The diversity of volcanic tuff buildings standing in Western Mexico is large, therefore, it was considered relevant to evaluate and synthetize different stone consolidants that could be applied in the regional weather conditions and renew the stability of those buildings; since the commercial products are developed and tested in foreign countries, and in some cases, when applied under the weather conditions of Mexico, the results differ from those reported. For the altered tuffs from Santa Mónica's Church in Guadalajara, Mexico, the deterioration mechanism of the local tuff was determined, thus a silicate and aluminosilicate consolidants were synthesized by the sol-gel method and applied to altered tuffs in order to evaluate their performance from structural to macroscopic level.  相似文献   

19.
The protective performances of two new fluorinated acrylic copolymers (based on the monomers 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDM) and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIM) are evaluated and compared with Paraloid B72, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA) and its partially fluorinated homologous 2,2,2-trifluoroethyl methacrylate/MA (TFEM/MA). The polymeric materials have been tested on Candoglia marble, a very low open porosity stone (<1%) used in Italian historical architecture (Milan Cathedral). The copolymers were tested according to UNI-Normal protocol. Measurements of capillary water absorption, static contact angles, colour variation and water vapour permeability were made before and after accelerated photo-ageing. FTIR spectroscopy and size exclusion chromatography (SEC) analyses were carried out on samples aged on inert substrate to assess the photostability of the copolymers themselves. The relationship between the protection efficacy and the fluorine content and distribution has been investigated. The results obtained show that the addition of a partially fluorinated co-monomer to the Paraloid B72 copolymer structure did not result in the expected improvement of the coating properties, while the fluorination of the copolymer side chain gave rise to encouraging performance.  相似文献   

20.
This study aims to introduce a new spectral imaging methodology that can be used to monitor on-line, non-destructively and in situ the cleaning level of pollution encrustation on stonework. The suggested technique is based on the optical properties of monochromatic light penetration in matter. The calculated differences of images, obtained at two different spectral bands, could reliably map the depth of cleaning. This novel approach was tested in the laboratory during laser cleaning trials on polluted stonework enabling high accuracy measurements (such as the detection of thin crust layers remaining on the under-cleaned marble surfaces). However, it may also apply for the monitoring of any other cleaning technique (micro air-abrasive, etc). A detailed presentation of the results will be demonstrated while the potential of its wide application on everyday conservation practice on stonework will be discussed.  相似文献   

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