Antonia Moropoulou

Abstract: In this work several specimens of mortars were prepared with the addition of 5% fly ash and 5% perlite and their mechanical properties and porosity were tested and compared to those of mortars with no additives (reference sample). Specifically, it was studied the influence that these additives have on the elastic modulus and porosity of the mortars. After conducting chemical, mineralogical and granulometric analysis of additives, a series of measurements were made in fresh and hardened mortars. In fresh mortars, measurements were conducted according to the EN1015-2/3/8 Standards concerning flow value, wet bulk density, air content, water demand and water retention. In hardened mortars, the measurements were made in the age of 28 days. The rate of carbonation and the formation of hydraulic phases were investigated using XRD, scanning electron microscopy (SEM) and thermal analysis (DTA-TGA). Porosity and pore size distribution of mortars were investigated by mercury intrusion porosimetry. Compressive and bending strength and adhesion were measured according to the EN1015-11/12 Standards. Finally, the Young's elastic modulus was measured in cylindrical specimens sized 50/100 mm (diameter/height) according to ASTM C469-02 Standard. The results of the present study indicated a differentiation in the microstructure of the mortars that can be contributed to the use of different additives, such as fly ash and perlite. The three materials proved to be compatible in their mechanical behavior and appropriate for construction use. The modulus of elasticity value is related to the ratio of compressive to flexural strength and in particular, with the increase of the value of the ratio, the value of the Young's modulus of elasticity increases. The development of the microstructure represents a major parameter to improve existing mortars and to formulate new mortars. © 2008 Elsevier Ltd. All rights reserved.

Abstract: The quantification of black crust formation on exposed stone has been carried out in this work with the aid of non-destructive analytical techniques. The proposed non-destructive Morphologically Fused Detection (MFD) approach, quantifies the deterioration effects encountered on marble surfaces by providing the number, location and shape of deterioration spots. According to this approach, a weighted difference of Gaussians filter determines the exact locations of deterioration patterns, a morphological detector provides the shape of such patterns and finally a conditional thickening operator combines location and shape information from the previous stages. The detected decay areas are segmented and distinguished into white and black spots according to their chemical composition. Besides applications in assessing deterioration and monitoring the decay rate of exposed stone with time, MFD can be further employed for evaluating the efficiency of cleaning methods. The algorithm is tested on a large set of images depicting a variety of degradation effects. The derived results are in accordance with assessments obtained by chemical analyses. © 2006 Elsevier Ltd. All rights reserved.

Abstract: Ceramic powder has been used as an artificial pozzolanic addition, in preparing pozzolanic mortars for the historic/traditional structures' construction. In order to evaluate the pozzolanic activity of ceramic powder, several pastes were prepared, by mixing it with hydrated lime, in different ratios. The pastes were stored in standard conditions (RH=99±1%, T=25±1°C) and evaluated using thermal analysis (DTA/TG), X-ray diffraction (XRD), compressive strength tests and mercury intrusion porosimetry (MIP), in time. The obtained results revealed that the compounds formed were CSH and C₄ACH₁₁ (monocarboaluminate) after 270 days of curing. The calcium hydroxide consumption increases as the initial amount of the ceramic powder in the paste augments. The maximum strength development is obtained for ceramic powder/hydrated lime ratio 3:1. © 2008 Springer Science+Business Media, LLC.

Abstract: In the present paper, the potential of the Greek building sector is examined using the energy and exergy analysis methodology. The building sector can play a crucial role in the efforts towards sustainable development. The building sector plays a significant role in the Greek economy as it engages more than 310,000 employees and 32,500 engineers (2003). The building sector has been one of the most rapidly developing sectors of the Greek economy in the last few years. The construction sector contributes significantly to the gross national product in 2005 (10%), notably higher when compared to 1997 (6.4%). Continuously increased energy consumption in the construction sector over the past 40 years (1961-2001) shows that this industry remains steadily in the ascendant. The aim of the present study is to analyse the energy and exergy utilisation in the Greek building sector in order to gain awareness of the sector's efficiency. © 2008 Inderscience Enterprises Ltd.

Abstract: In this work, several non-destructive testing and evaluation (NDT&E) techniques along with scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS) were applied on Pentelic marble surfaces. The investigated Pentelic marble surface disclosed a representative decay pattern that usually develops in polluted urban atmosphere such as the Athens centre. The applied techniques aimed to collate as much as possible evidence about the physico-chemical and aesthetical characteristics of the examined surfaces before and after the pilot cleaning treatments, in an attempt to configure an effective assessment methodology of cleaning interventions. The applied NDT&E techniques were fibre-optic microscopy, colourimetry and laser profilometry. The results were encouraging enough to propose the use of these NDT&E techniques along with SEM-EDS as an everyday assessment tool of cleaning conservation interventions on Pentelic marble. Copyright © 2008 John Wiley & Sons, Ltd.

Abstract: This paper examines a novel approach of corrosion damage analysis based on image processing for quantitative and qualitative evaluation of degradation effects on stone surfaces. This methodology can be applied in situ in association with a variety of non-destructive monitoring schemes, and on images acquired from several imaging modalities, capturing from micro- to macro-scale characteristics. Our analysis methodology was evaluated on three non-destructive monitoring techniques of cleaned and not cleaned stone surfaces, namely on digital camera, reflectography and fiber optic microscope images. Further to validating the potential of the various imaging modalities, the paper also assesses the corrosion rate and the efficiency of the recruited cleaning methods. The derived results are in accordance with chemical analyses revealing the deterioration patterns of the studied surfaces. © 2006 Elsevier Ltd. All rights reserved.

Abstract: The seasonal moisture transfer to and from the walls of a building is the most important factor concerning the deteriorating effect of moisture in buildings envelopes. The presented simulator takes into account the (a) moisture transfer mechanisms to and from the building (capillary rise, drying, etc.), (b) wall configuration (materials and size), (c) construction materials properties, (d) seasonal region meteorological data (air temperature, humidity and velocity) and calculates the (a) seasonal wall moisture content along with the corresponding equilibrium moisture height, (b) capillary rising water flow rate, (c) wall drying flow rate, etc. The simulator has been developed in an Excel platform in a user-friendly environment and consists of four units: (a) process model, (b) problem solution algorithms, (c) database and (d) graphics interface. The proposed simulator is a powerful tool in decision-making concerning the building deteriorating evolution and the selection of appropriate protecting strategy, e.g., the plaster selection (material, size, replacing time), contributing to the sustainability of masonries. © 2005 Elsevier Ltd. All rights reserved.

Abstract: Moisture transfer is one of the most important factors related to the energy performance, indoor quality, and maintenance of buildings. HygroScope is a simulator that takes into account the moisture transfer mechanisms, the wall configuration, the construction materials properties, and seasonal meteorological data for the region and calculates the seasonal wall moisture content along with the corresponded equilibrium moisture height. HygroScope is an application developed under Visual Studio 2005 using the C# programming language and consists of three units: the database, the mathematical model library, and the graphical user interface.

Abstract: In this work, digital processing of scanning-electron-microscopy images utilized to assess cleaning interventions applied on the Pentelic marble surfaces of the National Archaeological Museum and National Library in Athens, Greece. Beside mineralogical and chemical characterization that took place by scanning-electron-microscopy with Energy Dispersive X-ray Spectroscopy, the image-analysis program EDGE was applied for estimating three evaluation indexes of the marble micro-structure. The EDGE program was developed by the U.S. Geological Survey for the evaluation of cleaning interventions applied on Philadelphia City Hall. This computer program analyzes scanning-electron-microscopy images of stone specimens cut in cross-section for measuring the fractal dimension of the exposed surfaces, the stone near-surface fracture density, the shape factor (a surface roughness factor) and the friability index which represents the physico-chemical and physico-mechanical stability of the stone surface. The results indicated that the evaluation of the marble surface micro-structure before and after cleaning is achieved by the suggested indexes, while the performance of cleaning interventions on the marble surfaces can be assessed. © 2007 Elsevier Inc. All rights reserved.

Abstract: In order to evaluate the pozzolanic activity of metakaolin, several pastes were prepared, by mixing metakaolin with hydrated lime, in different ratios. The pastes were stored in standard conditions (RH=99±1%, T=25±1°C) and evaluated using thermal analysis (DTA/TG), X-ray diffraction (XRD), compressive strength tests and mercury intrusion porosimetry (MIP), in time. The obtained results revealed that the compounds formed are CSH, C₂ASH₈ and C₄ Ä€CH₁₁ while C₄AH₁₃ was not detected up to 270 days of curing. The calcium hydroxide consumption increases as the initial amount of the metakaolin in the paste augments. The maximum strength development is obtained for metakaolin/lime ratio:1. © 2006 Akadémiai Kiadó.

Abstract: In this work, active infrared thermography was employed in the investigation of various building materials. Different types of building materials were assessed: three types of porous stone (from Rhodes, Cyprus and Rethymno-Crete) and one type of marble (Dionysus). The investigated samples contained self-induced discontinuities of known dimensions and depths. During the investigation, the specimens were heated externally (thermal excitation) and thermograms were recorded continuously at the transient phase. Mathematical thermal modeling enabling the modeling of the investigated subsurface discontinuities, using 3D software, was also implemented. Then, quantification analysis (that is, temperature versus time plots, as well as thermal contrast curves) from the experimental tests, as well as from the use of thermal modeling runs took place, indicating the thermal behavior of building materials containing such discontinuities.

Abstract: The presence of water in masonry is one of the main factors in deterioration. Capillary rise is the most usual mechanism of water penetration into building materials. In this study the kinetics of the capillary rise phenomenon was studied for various building materials: four stones, two bricks, and six plasters. A first-order kinetic model was proposed, in which the equilibrium moisture height derived from Darcy law. The capillary height time constant found to be strongly affected by the material characteristics. Moreover, the capillary height time constant can be predicted if the average pore radius of the materials is known. © 2004 Elsevier Inc. All rights reserved.

Abstract: In this research, restoration mortars with analogous chemical composition of binders, aggregates and mineral additions, as they derive from the study of historic mortars, were evaluated regarding the strength development and the lime reaction, up to 15 months of curing. For this purpose several mixtures were tested in laboratory regarding their chemical and mechanical characteristics. The obtained results show that most of them present a slow rate of chemical and mechanical evolution, with the exception of hydraulic lime mortar and mortar with lime putty-natural pozzolanic addition. The best mechanical behavior was observed in mortars with lime powder and lime powder-artificial pozzolanic addition. These materials present also a low ratio of compressive to flexural strength (f_c/f_f). Further investigations on these materials would determine the time where their chemical and mechanical characteristics become stable. Only at that time, it would be possible to compare the compatibility characteristics of the restoration mortars with those employed in the past. © 2004 Elsevier Ltd. All rights reserved.

Abstract: Moisture is one of the most deteriorating factors of buildings. The deteriorating effect of moisture occurs mainly during the drying phase, and not in the wetting phase. Appropriate parameters of the drying kinetics are required for the building materials. Environmental factors, such as air temperature, air humidity, and air velocity affect drying. An experimental air dryer of controlled drying air conditions was used to investigate the drying performance of 4 stone materials, 2 bricks and 7 plasters. Drying kinetics was examined at 4 air temperatures, 6 air humidities, and 3 air velocities. A first-order kinetics model was obtained, in which the drying time constant was a function of the drying conditions, and the equilibrium material moisture content was described by the Oswin equation. The parameters of the proposed model were found to be affected strongly by the material and the drying air conditions. The results obtained are very useful in selecting the appropriate plaster to protect existing historic buildings.

Abstract: Mortars and concretes employed in ancient structures concern composite materials which have exhibited excellent durability through time. They were used as lining materials in cisterns, wells, aqueducts, shafts and duct drains, as supporting materials for pavements and mosaics, as plasters on external and internal walls, as supporting materials for frescoes and as joint mortars on masonry structures. They were comprised of various binding materials (or mix of them) and natural or artificial aggregates, along with natural or artificial pozzolanic additions, primarily of volcanic origin, that improved their performance and prolonged their longevity. Moreover, various types of organic substances were employed to increase plasticity and regulate setting rates, while fibrous materials were commonly used to obtain greater strengths or to avoid cracks due to the shrinkage during setting. The comprehension of the production procedures employed and of the physico-chemical and mechanical characteristics of such composite materials can be achieved by integrating properly the results of various analyses. Data obtained from tests performed on a large number of historic composites sampled from ancient structures in the Mediterranean Basin permitted the identification of physico-chemical and mechanical characteristics of the most typical mortars encountered in ancient structures. © 2004 Elsevier Ltd. All rights reserved.

Abstract: Moisture is one of the most deteriorating factors of buildings. The deteriorating effect of moisture occurs mainly during the drying phase, not in the wetting phase. Environmental factors, such as air temperature, air humidity, and air velocity affect drying. An experimental air dryer of controlled drying air conditions was used to investigate the drying performance of 4 stone materials, 2 bricks, and 6 plasters. Drying kinetics was examined at 3 air temperatures, 5 air humidities, and 3 air velocities. A first-order kinetics model was obtained in which the drying time constant was a function of the drying conditions, and the equilibrium material moisture content was described by the modified Oswin equation. The parameters of the proposed model were found to be affected strongly by the material characteristics. Copyright © 2005 Taylor & Francis, Inc.

Abstract: In this paper, we propose a new kinetic model that describes the depolymerization of pure cotton cellulose, applicable to ageing experiments in sealed vessels. By recording the pH of the salt solutions used for controlling the relative humidity inside the vessels, we demonstrate that volatile acidic species are produced during the ageing of pure cellulose. Based on the proposition that the acids produced must have an autocatalytic effect on the depolymerization of cellulose, we theoretically developed equations describing the time dependence of the percentage of the broken glycosidic bonds, the folding endurance, tensile strength, tensile energy absorption, stretch at break and the L* and b* coordinates of the CIEL*a*b* color system. The experimentally determined values of these pure cellulose paper properties were fit into the model equations by use of a computer statistical package. The very high values of the regression coefficients indicate that the model equations work quite well. The experimental data and the model equations indicate that for long ageing times (up to 150 days at 80 °C), the deterioration of the sample properties accelerates and finally brings about an abrupt breakdown of the samples. Under the light of these findings, we believe that the useful life of the historical paper stored in archives and libraries is less than predicted by the existing models, and steps for its preservation should be taken immediately. As an additional preservation measure, we propose the ventilation of the storage areas so that the volatile acidic products of paper deterioration that accelerate its ageing are removed. © Springer 2005.

Abstract: Moisture is one of the most deteriorating factors of buildings. The masonry moisture content depends on hygroscopic equilibrium between building materials and environment. Moisture sorption (adsorption and desorption) isotherms of 4 sandstones, 2 bricks, and 6 plasters were determined at 15, 25, and 35°C. A modified Oswin equation was used to predict experimental data for water activity in the range between 0.03 and 0.90. The hysteresis phenomenon between adsorption and desorption was observed for all the examined materials and classified at various isotherm types. A correlation of the hysteresis type with the microstructural characteristics of the materials was attempted. Copyright © 2005 Taylor & Francis, Inc.

Abstract: Traditional pozzolanic mortars such as those from Rhodes, Greece, or Hagia Sophia, Turkey, revealed the presence of a calcium-silicate-hydrate (C-S-H) binding phase. This phase, which is similar to that found in ordinary Portland cement (OPC), is produced under the pozzolanic reaction of slaked lime with fine reactive siliceous sources at temperatures <100 °C. The traditional siliceous sources were replaced by fumed silica or tetraethyl orthosilicate (TEOS). A microstructural analysis revealed an enhanced reaction rate but similar morphologies of the resultant C-S-H phases, confirming that the reaction-limiting factor is the dissolution of the siliceous sources. © 2003 Elsevier Ltd. All rights reserved.

Abstract: Infrared thermography has been used to monitor various porous materials in the laboratory during capillary rise tests, with the intention of evaluating non-destructively the presence of moisture. Supplementary techniques for investigating the porous materials in terms of their microstructure (mercury intrusion porosimetry) and isothermic behaviour (water sorption) were also used. Also, outdoor thermographic surveys were performed on historic structures in order to assess conservation treatments such as stones' consolidation. Finally, the emissivity values of the investigated materials were considered, as determined in the laboratory on collected samples.

Abstract: Three dimensional (3D) laser profilometry (LP) and pulsed thermography (PT) were used in the inspection of Pentelic marble. Quarry Pentelic marble samples, after processed with different roughness treatments (i.e. 60, 80, 100, 220, 400 and 600 mesh), were evaluated in the laboratory. Furthermore, different surface cleaning treatments were applied to a Pentelic marble surface in situ and then representative samples were collected and evaluated in the laboratory by the means of these two non-destructive techniques. Quantitative analysis of all samples was performed. The surface roughness parameter Rq at a specific length scale was estimated by the use of the LP scanning approach. Furthermore, 3D micro-topography plots from the laser scans were attained. PT, through the formation of temperature - time plots that display the intensity of pixels as a function of time on the obtained thermal images, was able to distinguish the influence of the applied roughness treatments. Results indicate that these two non-contact and non-destructive techniques can be used for the assessment of surface roughness. © 2004 Elsevier Ltd. All rights reserved.

Abstract: In this research, the pozzolanic activity of natural and artificial pozzolan used for preparation of restoration mortars was evaluated. For this purpose, several pastes were prepared, by mixing two artificial pozzolans and a natural one with commercial hydrated lime, in different ratios. The pastes were cured in standard conditions (RH = 98%, T = 25°C). The pozzolanic activity was evaluated by using simultaneous differential thermal and thermogravimetric analysis (DTA/TG) after curing for 3, 7, 14, 28 days. The obtained results revealed that the various lime/pozzolan pastes displayed different reaction kinetics and therefore the various pozzolans present different reactivity, in proportion to its mineralogical, physical and chemical characteristics. © 2004 Elsevier B.V. All rights reserved.

Abstract: The evaluation of consolidation treatment efficiency in terms of improving the resistance of treated lithotypes to deterioration phenomena caused by soluble salts crystallisation, is taking place through dynamic artificial weathering accelerated tests of marine salt spray. Quarried biocalcarenites from Greece and Cyprus have been treated with four consolidation materials (diversified according to their deposition mechanism). The materials applied are colloidal dispersion of silica, pre-hydrolysed ethyl silicate with amorphous silica, ethyl silicate in ethanol and acryl-siliconic resin in organic solvents. The treated stone samples are placed in an artificial weathering chamber, where they remain for nearly two months, being attacked by severe quantities of marine salt spray. The application of non-destructive techniques (weight and ultra sonic velocity measurements, deteriorated surface analysis by a camera-laser scanning system) during the salt spray simulations verified the improvements presented to the consolidated biocalcarenite samples in comparison to the untreated ones. Consolidated samples present weight stability during the tests, increase in ultra sonic velocity and minor fluctuations on it, and less roughness increase and grain detachment during the simulations. Deductions among the consolidants are made indicating the superiority of ethyl silicate as an appropriate consolidant for those biocalcarenites, as it has arisen from these certain tests.

Abstract: Nowadays, composite components and reinforcements are widely used in aircraft repair technology, since they present more efficient performance than conventional repairs. Composite patches (carbon or boron fibres) have been used for many years, mainly for research purposes, in aircraft maintenance. This move towards composites is mainly because of the increased mechanical performance, less corrosion and fatigue problems, allowing for longer service life of the aircraft. In this work, the technology and use of composite patching was described and reviewed. Furthermore, since the detection of structures integrity under patch, during the service life of aircraft, by non-destructive means is considered of great importance, infrared thermography was used for the detection of simulated artificially introduced damages - cracks, on the surface of Al 2024-T3 aircraft skin panels under composite patching or simulated delaminations between two plies of composite patches. Finally, real-time monitoring of damage during fatigue loading using thermography was also discussed and attempted in the laboratory on aircraft repaired panels. © 2003 Elsevier Science Ltd. All rights reserved.

Abstract: Salt weathering can be a hazard with significant cultural and economic implications. Salt-induced deterioration of architectural heritage is considered to be accelerated drastically in marine environments. This article investigates the weathering mechanisms and weathering forms in two calcareous stone types used in monuments and buildings on the SW coast of France. The mineralogical, chemical, textural and pore-system characteristics of freshly quarried and decayed stones from quarry, monuments and buildings were determined, and salts loading identified. The stones' resistance against salt weathering was estimated by comparing calculated crystallisation pressures, which are function of the pore size distribution, with the tensile strengths measured by Auger [Alteration des roches sous influence marine; degradation des pierres en oeuvre et simulation acceleree en laboratoir. These Doctorat d'Etat es Siences. Universite de Poitiers, France (1987)]. Results show that Crazannes sparite and La Pallice micrite behave differently with respect to water and salt-spray absorption and local salt precipitation since their pore networks, which control hydric properties, are different. Therefore, diverse weathering patterns due to salt crystallisation pressures were identified in the stones as influenced largely by their pore size distribution: alveolar weathering and granular disintegration in the sparite vs. flaking and micro-fissuring in the micrite. These mechanisms operate in response to salt inputs from a variety of sources - mainly marine aerosols and atmospheric pollution - as corroborated by the so-called enrichment factors (EFs). Wind is believed to trigger alveolar weathering in the heterogeneous sparite. Short-term observations in La Pallice micrite show rapid salt-induced breakdown through 'fatigue' effects. Determining factors involved in stone deterioration is important in the design of proper interventions for protecting historic buildings. © 2003 Elsevier Science Ltd. All rights reserved.

Abstract: A saline-spray artificial ageing test was used to simulate the effects produced in granites and sedimentary rocks (calcarenites, micrites and breccia) under conditions in coastal environments. Three main points were addressed in this study: the durability of the different kinds of rock to salt decay, the resulting weathering forms and the rock properties involved in the weathering processes. For this, mineralogical and textural characterization of each of the different rocks was carried out before and after the test. The soluble salt content at different depths from the exposed surfaces was also determined. Two different weathering mechanisms were observed in the granite and calcareous rocks. Physical processes were involved in the weathering of granite samples, whereas dissolution of calcite was also involved in the deterioration of the calcareous rocks. We also showed that microstructural characteristics (e.g. pore size distribution), play a key role in salt damage, because of their influence on saline solution transport and on the pressures developed within rocks during crystallization. Copyright © 2003 John Wiley & Sons, Ltd.

Abstract: Mortars from monuments of various periods in Crete, from Minoan up to now, have been studied (concerning mineralogical and chemical composition, grain size distribution, raw materials, tensile strength) in order to assess their durability in a marine and humid environment. The lime technology and raw materials, irrespective of the various historic periods, diversify the final composites into mortars, such as: (a) lime, (b) hydraulic lime, (c) lime with crushed brick, and (d) lime with pozzolanic material. These present binders in quantities ranging from 22% (pozzolanic mortars) to 29% (lime mortars). Hydraulic compounds, such as calcium silicate/aluminate hydrates, and tensile strength are higher in the pozzolanic mortars followed by crushed brick lime, hydraulic lime, and lime mortars. High quantities of water-soluble salts identified in the lime mortars indicate their risk of disintegration. A calculation procedure is presented herein, based on the combination of mineralogical and chemical analyses that allows the determination of the binder/aggregate proportion. © 2002 Elsevier Science Ltd. All rights reserved.

Abstract: In the last 25 years, there have been considerable efforts put into the use and development of infrared thermography on buildings and large structures. As a result, nowadays, there are systems that can be used effectively in outdoor and/or indoor building surveys; indication and monitoring of problems such as voids, detached areas, deposits of humidity, etc. However, the principal problem where infrared thermographic measurements are concerned is the emissivity - emittance of the material(s). Given that an infrared camera detects the radiation emitted by a material under investigation and renders this energy to a temperature - thermal image, the feature that describes the relation between the emitted radiation and the material's temperature, is termed as emissivity. Emissivity is actually a surface property that states the ability of the investigated material to emit energy. Correct emissivity values could provide valuable information concerning the interpretation of thermal images obtained from thermographic surveys. There is a considerable amount of work that has been published on emissivity of different materials and under various circumstances (i.e. temperature, surface condition, wavelength). In this work, a review on emissivity measurement techniques and the importance of emissivity values on building diagnostics was materialised. Furthermore, the emissivity of selected building materials were determined at a variety of temperatures, in the mid and long wavelength regions of the infrared spectrum, using different approaches and were discussed and explained in terms of the approach used, the wavelength and temperature effects, as well as the materials surface state. © 2002 Elsevier Science B.V. All rights reserved.

Abstract: This work uses multivariate statistics in an attempt to classify historical mortars in more or less distinct groups, depending on their physicochemical characteristics. Four types of mortars are studied: "typical lime," "cementitious," "crushed brick" and Portland cement. Fifty samples in total were analysed by thermal analyses (differential thermal analysis [DTA] and thermogravimetric analysis [TGA]), mercury intrusion porosimetry and mechanical strength tests. The results give us useful information on the understanding of the technology of historical mortars and planning syntheses for restoration ones. The inverse hydraulicity ratio (CO₂/structurally bound water, SBW) is correlated to CO₂ content (%) as measured by thermal analysis. The tensile strength increases with the amount of hydrated phases and the mechanical properties of the aggregate and the binder. Medians, ranges and extremely rare values were determined for each property showing compact groups. These groups were discriminated by principal component analysis (PCA) giving a tool for characterisation of historical mortars. © 2003 Elsevier Science Ltd. All rights reserved.

Abstract: Susceptibility of stone to salt decay is directly related to its microstructural and mechanical characteristics. In the present work, a porous stone from a quarry in Cyprus was examined. Samples of this stone were consolidated and protected with certain conservation materials. The modification of microstructural characteristics of the stone was evaluated by mercury intrusion porosimetry, while its mechanical characteristics were measured by compressive and bending strength tests. From these data, the susceptibility of Cyprus stone to salt (NaCl) decay was estimated. The values of crystallization pressure of NaCl were calculated and compared to the experimentally measured compressive and tensile strength of the stone, in order to examine the probability of stone disruption due to salt crystallization. The development of the phenomenon after coarse pores' filling with crystals, i.e. crystallization of salts in capillaries or mechanical failure of the stone, was determined by thermodynamic analysis. Additionally, artificial weathering tests of marine salt spray were performed for the evaluation of stone's durability after the conservation. The treated stone proved to be resistant to salt decay, as it presented ameliorated microstructural and mechanical characteristics, concerning decay due to soluble salt crystallization. The most possible thermodynamic scenario was small pores repletion with crystals, avoiding mechanical failure of the stone. © 2003 Elsevier B.V. All rights reserved.

Abstract: The objective of the study was to present the effectiveness of infrared thermography to a selection of applications. From the diagnostic studies that were performed, it was shown that infrared thermography could provide important information for the assessment of materials and structures.

Abstract: Since a large amount of damage in porous materials arises as a direct or indirect consequence of moisture (static and dynamic phenomena), detection and monitoring of moisture in porous materials is important, in an attempt to determine the actual damage, as well as the deterioration rate. The most common methodology to assess the moisture content in porous materials is to collect representative samples from the sites investigated and then weigh them before and after drying. In this research, infrared thermography, an indirect moisture assessment technique, was used in the investigation of various porous stones in the laboratory during capillary rise tests. Supplementary investigation of the stones in terms of their microstructure (mercury intrusion porosimetry) and isothermic behaviour (water sorption) was also performed. Finally, an in field diagnostic survey on historic structures was carried out. The results of this study indicate that infrared imaging provides significant information in the study of moisture in porous materials. © 2002 Elsevier Science B.V. All rights reserved.

Abstract: Bricks from the Agia Sophia in Istanbul, Turkey, were investigated to better formulate a plan for restoration. According to an ancient text, these bricks are extremely light and were manufactured on the island of Rhodes. Results of neutron activation analysis, grouped by multivariate statistics, show that the brick samples do not correlate with clays thought to be local and used in contemporary churches in Istanbul. The bricks are similar to those used in the Great Basilica of Rhodes. However, the Agia Sophia bricks are lighter (45% porosity) than the bricks from the other churches (35% porosity). The Agia Sophia bricks are made of a noncalcareous, fine paste with quartz temper, fired at low temperature (∼750°C). The exceptional characteristic is their homogeneity and small pore-size distribution (0.3-0.8 μm). The tensile strength of the dome bricks is unexpectedly high (up to 1.3 MPa), even though the bricks have high porosity.

Abstract: The main purpose of this research work was to determine the limits for the detection of defects on aircrafts components using thermographic techniques. Several notched (cracked) aluminium panels, repaired with defective or adequate composite patches, were assessed in the laboratory by active thermography with a view to detecting and identifying such imperfections. The patches applied on the aircraft panels were constructed of numerous plies of either boron epoxy or carbon epoxy composite materials. For the infrared thermographic investigation, the dual-wavelength active approach (3-5.4 μm and 8-12 μm) was employed, using either an external heating or cooling source. Moreover, thermographic image analysis, using histograms, was applied on a choice of thermal images for a two-dimensional measurement of the located deficiencies. The results obtained from this work demonstrate that thermography can be considered as a powerful non-destructive tool for the assessment of defects and patches on aircraft materials.

Abstract: Non-destructive techniques, such as infrared thermography and ground penetrating radar, have the potential to produce rapid and accurate assessment of airport pavements. In this work, an examination of asphalt pavements situated at the International Airport of Athens in Greece, is performed. Infrared thermography and ground penetrating radar are introduced with the purpose of providing prompt and accurate condition assessment of airport pavements. These techniques are used efficiently in the detection of cracks, voids and other imperfections appearing either from the ageing of the materials or due to poor workmanship. Finally, this paper describes the problem of deteriorating airport pavements, the procedure and the equipment used for the in situ tests, while the results obtained lead to the suggestion of a predictive monitoring non-destructive technique for the inspection and appropriateness of efficient engineering structures.

Abstract: Structural studies to determine the earthquake worthiness of Hagia Sophia in Istanbul have proved that the monument's static and dynamic behavior depends very strongly on the mechanical, chemical and microstructural properties of the mortars and bricks used for the masonry. Hence, the classification of the crushed brick/lime mortars under the category of advanced cement-based composites is concluded, explaining the fact that the monument still stands, as well as the very large static deformations which it has undergone, since such mortars have a very long curing period. According to the analysis of the dynamic data, the first three natural frequencies of the building were determined. These results show a decrease of approximately 5-10% in the natural frequencies, as the amplitude of the accelerations increases and returns to their initial values, due to the non-linear nature of the masonry. The above-mentioned behavior allows the structure to absorb energy without affecting irreversibly its material properties. The determination of the mortar properties indicated that they are of considerable mechanical strength and longevity. The dated mortar samples examined proved to be resistant to continuous stresses and strains due to the presence of the amorphous hydraulic formations (CSH), investigated by transmission electron microscopy (TEM) at the crushed-brick powder/binder interfaces and at a sufficient content in the binding matrix, as proved by TG-DTA, which allowed for greater energy absorption without initiations of fractures, let alone the transition of the gel to a higher order of formation. Furthermore, the interpretation of the amorphous nature of the hydraulic formations of the crushed brick/lime mortars is attempted by the experimental validation of real chemical interaction between lime and clay and the characterization of the fundamental structural units of the calcium silicate hydrates, produced by mass spectroscopy. © 2002 Elsevier Science Ltd. All rights reserved.

Abstract: Ni/8 mol% Y₂O₃-stabilized zirconia cermets are used in thin-film electrolyte solid-oxide fuel cells as support substrates. Rapid oxidation of the metallic Ni can cause failure of the substrate and of the whole system. The rate of Ni oxidation in air and in an inert atmosphere containing water vapor was determined as a function of temperature between 500 and 950°C. A logarithmic rate law describes the oxidation kinetics in air, whereas a linear rate law fits the first branch of the curve of the experimental data in a humidified inert atmosphere. The substrate exhibits no significant mechanical degradation after uniform oxidation under moderate conditions. However, the observed bending of the samples after oxidation in humidified argon, due to the nonuniform oxidation, can cause damage to fuel cell.

Abstract: Surface alterations of the original limestone and the efficiency of several cleaning methods were investigated on the Corfu Venetian Fortress facade. Black crusts of gypsum dendrites and loose depositions or black-grey calcareous encrustations in combination with biological decay were identified as main decay processes. The cleaning treatments, chosen according to their acting on the stone surface, were: sepiolite for solvent action, ammonium bicarbonate for exchange action, EDTA for the chemical chelating action, hydrogen peroxide for chemical action on biological species and nylon brushes for physical action. Each cleaning method's efficiency and counteractions were evaluated by laboratory examinations concerning the morphology and the composition of the surface with SEM observations and X-ray microanalysis, before and after treatment and during ageing tests in sulphur dioxide and humidity atmosphere. The used methodology creates a sound basis for the evaluation and proper selection of a cleaning method, which should be highly efficient and with limited counteractions to the stone. © 2002 Published by Elsevier Science Ltd.

Abstract: The facades of the Bank of Greece historic building, mainly consisted of porous stone, gray marble and white pentelic marble, are subjected to an intensive air pollution attack in the center of Athens. A diagnostic study was carried out prior to the cleaning procedures for the weathering evaluation. Weathering appears mainly as black depositions, salt crusts, and oily depositions, due to the heavily polluted urban atmosphere from the nearby traffic. Previous improper cleaning treatment by water spray under high pressure caused detachment of grains and fissuring which were recognized as mechanical abrasion of the surfaces. In this study, a pilot investigation is performed with the intention of evaluating the most appropriate cleaning treatment. Therefore, several cleaning procedures were performed in the laboratory and in situ for the evaluation of methods and products applied on the facades. Both chemical and physical cleaning procedures were applied and they were chosen for their selective action: only water and sepiolite for solvent action, ammonium bicarbonate for exchange action, EDTA for the chemical chelating action and microblasting for physical action were used. In situ non-destructive evaluation was performed by Fiber Optics Microscopy in order to assess the counteractions of each cleaning method to the original surfaces. Digital Image Processing was also used to account for the efficiency of each cleaning method. © 2002 Elsevier Science Ltd. All rights reserved.

Abstract: This study has examined the effects of limestone characteristics (microstructure and texture) and calcination temperature on the reactivity of the produced quicklime. Two types of limestone have been calcined at four selected temperatures (900°C, 1000°C, 1100°C, 1200°C), and the produced quicklime was slaked. Chemical, physical, and mineralogical analyses have been performed in limestone, quicklime, and slaked lime samples with the intention of studying the quicklime reactivity. Test results indicate that the lower the limestone calcination temperature, the more reactive the produced quicklime. The optimum calcination temperature is ∼900°C, which was the temperature performed in traditional limekilns. Concerning the quicklime, the reactivity is related to its microstructure, which is, in turn, related to microstructural characteristics of the limestone (texture, grain size, porosity). The most reliable factors for the estimation of quicklime reactivity are the specific surface area of the quicklime and the rate of temperature increase during the slaking process. © 2001 Elsevier Science Ltd.

Abstract: With a view to the strict preservation regulations for mosaics and historical sites in general, only non-destructive techniques ought to be employed for significant data collection. Besides the conventional uses of non-destructive techniques, for decay diagnosis, quality assessment, and so on, information concerning plastered mosaic surfaces can be obtained from NDT techniques such as ultrasonics, ground penetrating radar, microwave reflectometry and infrared thermography. Special considerations regarding the applicability and accuracy of these techniques for this specific application are presented. The results of this laboratory research work should lead to the development of an integrated non-destructive assessment method for on site investigations on plastered mosaic surfaces.

Abstract: Since delaminations in airport pavements can lead to failure, cost effective ways must be suggested to inspect the quality of pavements. One of these cost effective ways is the infrared thermography technique. This research paper covers the determination of delaminations in asphalt pavements situated at one of the busiest airports in Greece, the International Airport of Athens, by means of infrared thermography. The infrared thermographic technique is used efficiently in the detection of cracks, flaws and other imperfections appearing on airport pavements. The outcome of this investigation leads to the proposition of a forecasting non-destructive technique intended for assessment of efficient airport pavements. © 2001 Elsevier Science Ltd.

Abstract: The structure and physicochemical characteristics of weathered surfaces of marble in industrial environments can be attributed to the interconnected evolution of the processes taking place at the atmospheric environment - marble interface. The present work is an attempt to correlate the aerosols of a heavily polluted atmosphere with the different weathering patterns observed on marble surfaces. Energy Dispersive X-Ray Fluorescence, X-Ray Diffraction, Porosimetry, Atomic Absorption, Atomic Emission Spectrometry, Ion Chromatography, Optical Microscopy and Scanning Electron Microscopy results were used together in principal component and discriminant analysis. These analyses were performed on forty six samples of aerosols and eighteen samples of crusts. Other parameters like orientation of the weathered surface, exposure to rainfall, presence of recrystalised calcite and gypsum were also used. The samples were collected from the archaeological site of the Sanctuary of Demeter, located near Eleusis (west of Athens, Greece), where a great number of industries (mainly metallurgical and chemical) cause several environmental problems. The results provide invaluable information on the nature of marble surface decay. The elements determining the chemical composition of the coarse airborne particles are Ca, Si, S, Br and Cl. The presence of gypsum is strongly related to black crusts or loose deposits. Y, Mn and rain exposure, are correlated with each other and related to black-gray crusts. Ca and Sr are correlated with washed-out surfaces. Finally discriminant analysis is proved to be a powerful tool in prediction of the type of decay that will be occur on a marble surface, given the composition and type of the polluted atmosphere.

Abstract: It is well known that even though historic mortars present low strength and elastic moduli they confer durability to the structures surviving today. The present work investigates the durability of historic mortars in relation to the production technologies employed. Thermal analysis allows for classification of historic mortars in both lime and hydraulic types. Mineralogical data, concerning fabrication and texture, along with thermal analysis provide criteria on specific classification, for: typical lime, crushed brick-lime, cementitious, rubble masonry, hot lime technology and gypsum mortars. The correlation of the measured tensile strength (fmt, k) with the estimated CO₂/structurally bound water ratio, indicates direct proportionality to the levels of the hydraulicity. Physico-chemical adhesion and cohesion bonds, studied by SEM-TEM/EDX, developed at the matrix and at the binder/aggregate interface, respectively, becomes the key factor in interpreting the considerable durability that the historic mortars confer to the structures as bearing elements.

Abstract: In the present work, infrared thermography is applied and investigated as a non-destructive tool in the evaluation of materials and techniques for the protection of historic monuments. A diagnostic study on historic monuments and buildings, situated in Greece, is performed. Long-wave infrared thermography (8-12 μm) is applied on advanced and historic materials regarding architectural surfaces and historic structures for research purposes such as: (i) The assessment of humidity impact on porous stone masonries. (ii) The evaluation of conservation interventions (materials and techniques) regarding: consolidation interventions on porous stone masonries; restoration of masonries by repair mortars; and cleaning of facades.

Abstract: Cholesteric liquid crystals have been used to study the weathered surfaces of marble from the Sanctuary of Demeter in Eleusis, near Athens. Previous investigations have shown that when a cholesteric phase is spread across the surface of the stone, the pitch of the mesophase is sensitive to the topography of the surface. The wavelength of the maximum in the reflected spectrum varies therefore with the microtexture of the surface. Small samples of surface stone from the temple which had been weathered in distinctive ways, were investigated in the laboratory. There appears to be a significant correlation between the optical reflectance spectra and the surface microtopography investigated by SEM, as indicated by computer aided analysis (Digital Image Processing). The results point to the development of an effective in situ method of monitoring the weathering of marble surfaces using cholesteric liquid crystals.

Abstract: The study of the behaviour of historic buildings that have suffered from earthquakes has become a valuable tool for the understanding of earthquake resistant construction techniques and materials. Byzantine monuments of the 11-13th century in Kiev have been studied to provide insights into their effective dynamic properties facing severe earthquake history in the area. The recessed brickworks according to the 'concealed course' construction technique of the St. Sophia Cathedral (11th century), the Church of St. Michael in the Vydubytskyi Monastery (11th century), the Tithe Church of the Assumption of the Virgin (10th century) and the Cathedral of Assumption of the Virgin (11th century) in the Monastery of the Caves (Pecherskyi monastery) in Kiev were studied and the material properties of bricks and lime mortars with ceramic fill were investigated (mechanical strength tests, mineralogical, chemical and microstructural analysis). The results show major similarities with those of the Byzantine monuments in Istanbul (Theodosian Walls and Hagia Sophia - 6-11th century construction phases), giving evidence of earthquake resistant construction techniques and materials allowing for continuous stresses and strains. Hence, didactics on proper restoration techniques and materials are deduced aiming at their present safety in the face of future earthquakes. (C) 2000 Elsevier Science Ltd. All rights reserved. The study of the behaviour of historic buildings that have suffered from earthquakes has become a valuable tool for the understanding of earthquake resistant construction techniques and materials. Byzantine monuments of the 11-13th century in Kiev have been studied to provide insights into their effective dynamic properties facing severe earthquake history in the area. The recessed brickworks according to the `concealed course' construction technique of the St. Sophia Cathedral (11th century), the Church of St. Michael in the Vydubytskyi Monastery (11th century), the Tithe Church of the Assumption of the Virgin (10th century) and the Cathedral of Assumption of the Virgin (11th century) in the Monastery of the Caves (Pecherskyi monastery) in Kiev were studied and the material properties of bricks and lime mortars with ceramic fill were investigated (mechanical strength tests, mineralogical, chemical and microstructural analysis). The results show major similarities with those of the Byzantine monuments in Istanbul (Theodosian Walls and Hagia Sophia - 6-11th century construction phases), giving evidence of earthquake resistant construction techniques and materials allowing for continuous stresses and strains. Hence, didactics on proper restoration techniques and materials are deduced aiming at their present safety in the face of future earthquakes.

Abstract: Infrared thermographs coordinated with the results of chemical analysis of stone decay products (soluble salts-ion concentrations) and the results of humidity contents permits to evaluate environmental impact assessment on historic masonries. Hence, it provides information in order to assess incompatible environmental management and to valuate new uses of cultural goods. A G.I.S. application on the Medieval Fortification of Rhodes was developed by the NTUA - Materials Science and Engineering Section, using Arc/Info software for the display, query and generally management, of these data. A raster image of the old city serves as the main orientation base map, while measurements of distance and area can be displayed directly on a vector map. These can then be functionally seamlessly integrated in the existing data base with the objective to identify any possible spatial relationships between the various variables (i.e. humidity versus distance from the underground sewage system), as well as to create a structure, which will be capable of accommodating future data and thus develop into a comprehensive and useful tool for data integration and analysis. Devaluating cultural heritage derives form the inevitable marine and urban atmosphere, but as well from the town planning related uses and incompatible environmental management. Environmental loads can be visualized in their spatial distribution in the raster map as salt spray sources, pollution sources and humidity sources.

Abstract: The salt crystal growth mechanisms in large heterogeneous systems are studied using weathered samples from various depths on masonries exposed to the sea. The samples are examined systematically under SEM and EPMA. Using the results, crystal growth patterns occurring during distinguished phases of the evaporation process within the porous stone masonry in depth are differentiated.

Abstract: Non-destructive investigation techniques are largely used because of the outstanding advantages that they are capable of providing in a variety of applications. NOT methods, such as fibre optics microscopy, infrared thennography, ultrasonics and digital image processing, are applied in the laboratory of Materials Science &amp; Engineering (Chemical Engineering Department), in the National Technical University of Athens (NTUA), on advanced and historic materials regarding arcliitectural surfaces and historic masonries, for research purposes such as: U materials quality control, as well as for technology assessment regarding the production of advanced materials⁽¹⁾ â–¡ environmental impact assessment - materials and weathering mapping⁽²⁾. â–¡ evaluation of conservation materials compatibility and conservation interventions effectiveness on the scale of architectural surfaces and historic masonries^[3,4,5,6]. â–¡ strategic planning for the conservation interventions[7,8,9]. â–¡ environmental management for the protection of cultural heritage^(10,11) It is found that the combined use of the applied nondestructive techniques can allocate information concerning mechanical properties, microstructitral characteristics, energy and mass transfer phenomena such as humidity capillary rise and evaporation, and so on. In addition, the application of these techniques can give precise interpretation of the actual physico-chemical phenomena, when combined to laboratory application investigation of critical parameters. A Geographic Information System (GIS) is used on the scale of large historic complexes, in order to manage a multidisciplinary database, including environmental, architectural, structural and materials data.

Abstract: The origin and growth of weathering crusts on the ancient marbles of ruins of the Sanctuary of Demeter in the industrial atmosphere of Eleusis in Greece have been investigated. A systematic mineralogical, petrographical and chemical examination of weathered stones and crusts was performed, both in situ and in the lab, on samples taken from different parts of the monument in relation to the surface characteristics as well as to the exposure to rain, sea-salt spray and wet and dry deposition of airborne pollutants and dust. In particular, the various material-environment interactions take place, are characterized by (a) disintegrated 'washed-out' surfaces, where products are taken away through dissolution, (b) rusty yellow patinas rich in Fe and Cu, (c) firmly attached black crusts in contact with percolating water, where recrystallized calcite shields amorphous deposits rich in S, Si, Fe and carbonaceous particles, (d) black loose deposits in the water sheltered areas, consisting mainly of gypsum and fly ash particles and (e) cementitious crusts, coating and pitting the horizontal surfaces. Moreover, an interconnected evolution of various physicochemical processes is shown, characteristic of the origin and growth of various crusts, which are formed and classified accordingly.

Abstract: The action of air pollution and environmental conditions on the weathering of historical monuments has been investigated for the site of the Demeter Sanctuary (1500 BC) in Eleusis, Greece. Total deposition and aerosols were analysed in relation to the concentration of elements in the various types of weathered stone crusts. The objective of the study was the evaluation of the origin of the elements and ions determined in aerosols and total deposition and to relate these to possible sources (soil, underlying rock, marine spray and anthropogenic activities) using enrichment factors.

Abstract: The mortars and 'cocciopesto' plasters were largely used in the historic buildings, as waterproof coverings and in the preparation of mortars, especially in horizontal structures. In recent years, the necessity of restoration interventions with materials which are compatible with the masonry structure requires a detailed study on these materials. In this study, the composition of a significative number of mortars of the Byzantine period in the Hagia Sophia Basilica are investigated. They were made of 'cocciopesto' (crushed ceramic) and probably have a bearing function in the masonry structure. The samples are examined by particle size, infrared spectroscopy (FT-IR) and thermogravimetric analyses (TG-DTG), both on the total sample and on the finer fraction (<63 μm) which mostly constituted of binder. The results indicate slightly hydraulic mixtures made with a binder/aggregate ratio variable in volume between 1/2 and 1/4. The mixture morphology and heterogeneity seem to imply the use of hot lime technology that would lend themselves to the bearing function of the mortar. © 1998 Elsevier Science B.V.

Abstract: In a previous work, the mechanism by which salt crystals grow in porous stone masonries has been studied. It has been shown that the pressure exerted by sodium chloride (NaCl) crystals on the pore walls, when the crystals have entirely filled the coarse pores (10 μm), is the cause of disruption. In the present work, the microstructural parameters controlling the destructive effect of NaCl crystallization in porous stones, and specifically NaCl crystallization in the highly porous biocalcarenite of the historic masonries of the medieval city of Rhodes, which occurs favourable, are studied. Samples from both quarries and monuments have been examined. Porosimetric measurements were performed in order to calculate the NaCI crystallization pressures on the basis of the thermodynamics of crystal growth from a supersaturated solution in a porous material. Comparison of the calculated values of the crystallization pressure and the experimentally measured compressive strength permits one to assess the probability of rock destruction by salt crystallization. Energy balance analysis was performed in order to evaluate whether the successive crystallization of NaCI filling the smaller pores or the disruption of the pore walls is the most probable scenario for the given operating conditions. The release of free energy during the spontaneous crystallization from a supersaturated solution has been compared with the mechanical energy needed for the material's destruction, and the susceptibility of porous stone to salt decay is shown to be a function of the mechanical and structural parameters (compressive strength, modulus of compressibility and pore size distribution). © 1997 Elsevier Science Ltd.

Abstract: Rubble masonry mortars are distinct to the masonry mortar joints due to the different construction techniques used and the prerequisites concerning their behavior in the structure. In the present work, physico-chemical and mineralogical examination of rubble masonry mortars is performed on the development of cohesion and adhesion bonds. A working hypothesis on production technology is deduced consequently. Recent collapses of the rubble masonry at several bastions of the knights' period in the Medieval fortifications of Rhodes allow for sampling. Investigations by optical microscopy, scanning electron microscopy, fiber optics microscopy, X-ray diffraction analysis, differential thermogravimetric analysis, porosimetry as well as total soluble salts measurements were performed. Various types of rubble masonry mortars are evidenced and all of them present a very coherent matrix, either 'cementitious' or very finely crystallised and compact. From the top to the bottom of the masonry, different microstructural characteristics are observed in the mortar nucleus, indicating different lime-to-aggregates ratios. The microstructural stratification of the cementing material points out different carbonation and drying levels and implies successive supply of water to slake the lime in situ. The evidence of hydraulic components all around the bulk, but not on the outer top of the walls, is of particular interest and proves the in situ slaking of lime as the energy source to activate either hydraulic reactions among lime and clay minerals or the crystallization of portlandite. The high levels of soluble salts measured indicate the mortars' susceptibility to salt decay, specifically when pore size distribution is in favor, as in the case of the modern cement or the pure calcitic mortar, in comparison with the more resistant hydraulic mortars. © 1997 Elsevier Science Ltd.

Abstract: A new design for solid oxide fuel cells (SOFC's) was developed aiming at the reduction of the total electrical resistance of the cell. The thickness of the electrolyte was decreased, while the anode took on the role of the substrate. The pore structure with respect to gas permeability of this component has to be optimized for the proper operation of this design. Anode substrates, consisting of a cermet (yttrium-stabilized ZrO₂ and metallic Ni) and produced by two different processes, coat mix and tape casting, were characterized with respect to pore structure (shape and mean radius), porosity (total, open and permeable), pore size distribution and air permeability. The following methods were used: (i) optical and electron scanning microscopy in combination with image analysis, (ii) mercury porosity, and (iii) air permeability. Correlations between air permeability and porosity and also the percentage of permeable pores in anodes show the superiority of coat mix samples to tape-cast ones. It has been observed that the coat mix process can produce anode substrates with interconnecting porosity, while tape casting, as used in this study, needs some modifications in order to be appropriate for this purpose.

Abstract: The capillary rise effect on brickwork not located along the canals has been studied in previous works in Venice. In the present work, arguments concerning the capillary rise effects on brickwork along the canals are being dealt with. The research program has been developed on walls of different typologies, building materials, historical periods of construction, position and exposure orientation as well as different conditions of maritime traffic. Brick specimens from various points in height and in depth were sampled and underwent physical and chemical examination. In particular, soluble salt concentration, composition and distribution within the wall was determined by Atomic Absorption Spectrophotometry and Ionic Chromatography. Various salts present were identified by FT-IR, while TG-DTA was employed to identify thermal decomposition products. Porosity, as a significant physical parameter for the physico-chemical phenomena, was measured by a mercury porosimeter. The results conclude that the phenomenon of capillary rise is very advanced, due to higher values of soluble salts in comparison with walls not in direct contact with the canals, and mechanical action is increasing the integral porosity.

Abstract: In previous works the mineralogical and physico-chemical properties of crushed brick-lime mortars in response to stresses, simulating earthquakes or dynamic soil structure interactions, were studied. It was proved that the effective mechanical properties of the mortars could be attributed to the alkali-silicate reactions occurring at the brick fragment-lime interface. Since the category of the pozzolanic mortars presents a wide spectrum, spanning from the crushed brick to various cementitious mortars, the idea was to study the effectiveness of other hydraulic mortars as well. The Symonos Petra Monastery at Mount Athos was selected for investigation as pilot monument, because in our previous works it was found to be scientifically sound. The mortars were analysed following a procedure correlating chemical and instrumental analysis to determine CaCo₃/CaOsil. TA, IR, SEM and EDX were performed and tensile strength and adhesion was measured. The amounts of Ca⁺⁺ and Mg⁺⁺ were determined by AAS. Old mortars, from the Arsenal tower (16th c.) present higher tensile strengths than traditional hydraulic lime mortars and are effective against dynamic stresses exerted onto the greater Serbomacedonian mass as well as against the intense marine environment. Fine ground magnesium-alumino-silicate dust of the montmorillonitic clays in the area could have been mixed in a ratio of 2/(1/5) of lime/'pozzolanic' or active clay admixtures/inert aggregates reacted with the in situ slaked lime, their hydraulic components augmenting considerably with Mg⁺⁺. Hence Arsenal mortars present an intermediary between Roman and modern concrete for marine structures produced by hot lime technology.

Abstract: Structural analyses of the Hagia Sophia, a sixth century masonry edifice, in Istanbul, Turkey, are coordinated with geotechnical and material investigations to provide insight into the structure's response to dynamic loads. The church contains four great brick arches springing from stone piers that offer primary support for a 31-meter diameter central dome and two semidomes. Stone and brick masonry material properties for the numerical model are adjusted to match system mode shapes and frequencies identified from measured response to a recent low-intensity earthquake. The calibrated model is used to predict the measured responses, and improvements achieved by incorporating soil-structure interaction are demonstrated. Stresses under simulated severe earthquake loading are estimated at the critical locations in the arches. The materials of the mortar are studied in detail using a number of preliminary microstructural, mineralogical, and chemical tests to support the choice of effective mechanical properties. The foundations of the main piers and soil surrounding them are studied through preliminary tomography experiments to support the modeling of soil-structure interaction. © 1995.

Abstract: Construction materials in historic buildings suffer from various physicochemical decay processes governed by their interaction with environmental parameters leading to quite a great variety of deterioration forms at several scales. In the present work, the establishment of a method for a statistically reliable correlation between the particular parameters which compose the microenvironment and the resulting decay form is attempted. The case of an extended monument, like the medieval city of Rhodes, where various characteristic types of weathering can be distinguished in relevance with the particular laws governing the relation between environmental and microclimatic conditions and materials, could act as a pilot. The results of ion chemical analysis for soluble salts along with sea and sun exposure and air flow, which control transport and evaporation of solutions in the stone, have been included in the data matrix describing the statistical problem. Discriminant analysis is employed using as data vector the above variables and entering as classification factor the variable Dectype. It is possible to classify a new case by evaluating each function, through the classification function coefficients, and assigning the case to the group corresponding to the highest function value. This classification is validated by the chemical analysis and the in situ study as well. Statistical analysis and especially multivariate methods could provide a technique for predicting what type of weathering would be expected according to the micro-environmental conditions at various locations. Hence, the directions of a conservation plan could be ascribed and evaluated accordingly.

Abstract: The Monastery of Symonos Petra, located in Athos mountain (Greece) was studied for geotechnical site investigation and building material weathering conditions. The site investigation comprised rockmass description and rock slope stability analysis. The interpretation of the collected data determined the probable surfaces of sliding that can be activated under specific conditions. Building stones and different types of mortar, used as cementing material, were collected from the older parts of the Monastery (13th and 16th century). These samples were examined regarding their origin so as the most suitable measures for preservation may be taken. © 1995.

Abstract: The characterization of mortar properties can be accomplished by the use of thermal analysis. DTA can be used to identify various component materials and observe the reactions associated with controlled heating of the mortar. This method reveals thermal transformations, which include dehydration, dehydroxylation, oxidation and decomposition. In addition, crystalline transitions can be observed, which are exothermic or endothermic in nature. With TGA, thermogravimetric analysis, the mass of the sample is monitored (weight loss) as a function of temperature. Weight losses at reaction temperatures near 750°C, indicate loss of CO₂ not from pure CaCO₃, but from recarbonated lime. The dehydroxylated clays acted as a "pozzolan" which imparts early strength to the mortar. However, a more complex phenomenon occurs in crushed brick mortar, since compounds of hydraulic type occur at the brick matrix interface also. The DTA and TG-DTG analyses identify the dehydration of calcium alumino-silicate phases, giving clear evidence of a cementitious mortar rather than one of pure lime. In the present work a spectrum of thermal and XRD analysis results from ancient, Byzantine, post-Byzantine and later historic mortars from Greece is presented and the relevant information concerning the characterization of traditional mortars is validated. Generally, the CO₂ bound to carbonates and the water bound to hydraulic components (in weight loss%) discern two groups of mortars, the typical lime and the hydraulic, respectively. The specific classification of mortars into groups with characteristic transformations indicated by weight loss against temperature, enables discernment of: typical lime, cementitious, with crushed brick, with portlandite, with gypsum, with modern cement or of hot lime technology, mortars. Mineralogical, microstructural, mechanical and technological data could provide further evaluation criteria. © 1995.

Abstract: The study of traditional mortars has recently been attracting considerable attention, in connection with both diagnosis and applications required for restoration. The mortar is only apparently a simple system; in reality the lime is often accompanied by hydraulic components. The inerts often interact with the binder and the technologies used in the application are very diversified. These situations make the study of the mixtures rather complex, as it is difficult to distinguish the neoformation compounds from the older ones. A basic approach is offered by granulometric analysis, allowing separation of the mortar into its components, in which the finer fraction is richer in binder. Some analyses on this fraction (<63 μm) were performed to define the nature and quantity of the binder in the mortar. Samples were taken from various sites in Venice and were examined by calcimetry, TG-DTG and FTIR analysis. Moreover the investigation of this fraction by optical microscopy enabled us to distinguish the binder from the inert particles. © 1995.

Abstract: The present work focuses on the investigation of mortar joints of historic masonries consisting traditionally of aerial binder and inerts which contain lumps. The presence of lumps, usually white in colour and of various dimensions, was often recorded inside these mixtures and does not appear to be random, as they are rather frequent, These lumps could confer some physicochemical properties to the mixture, that favour the overall compatibility of the system. For this purpose, various samples taken from historic Venetian masonry were examined by TG-DTG and FTIR analysis. Moreover SEM and fibre optical microscope observations were performed. The results indicate mainly the presence of completely carbonated lime and lead us to assume that the lumps arise from technologies based on the non-seasoning of the lime. © 1995.

Abstract: Ceramic materials represent manufacturing techniques which were improved consistently during the course of time. The components of ceramic materials are the "fingerprint" of the stable and/or metastable solid phases formed during the firing; the production processes of antique ceramics and pottery can be derived from their assemblage. There are many recognizable phases and their association depends, more than on their chemistry, upon the mineralogy of the raw materials, their grain-size distribution, maximum heating temperature, heating ratio, duration of firing and kiln redox atmosphere. All these factors help in understanding the "course" of reactions. Heating also affects the contact between the fine-sized clayey matrix and mineral clast fragments, appearing in reaction rims, sometimes showing newly-formed phases. The temperature at which ancient ceramics and pottery were fired varies over a wide range (600-1300°C) depending on the type of clay used and the kiln available, although firing temperatures not above 300-400°C have also been suggested. Clay minerals, as the main material for production of ceramics and pottery, show some characteristic reactions (dehydroxylation, decomposition, transformation) in the course of firing (heating effects) and several thermoanalytical criteria can be used for reconstruction of former production conditions. In the present work DTA, TGA and XRD results from byzantine and medieval ceramics are examined and information derived on ceramic technologies concerning raw materials and production conditions is validated by SEM observations concerning the extent of vitrification, as well as by the microstructural data provided by porosimetric measurements. © 1995.

Abstract: In this work infrared thermography was used as a diagnostic tool for the performance assessment of a photovoltaic array integrated on the southern façade of NTUA's Chemical Engineering Building. This grid-connected 50 kWp solar photovoltaic array, installed under an EC Thermie Project (SE-142-97-GR-ES), operates in a standard and hybrid PV-Thermal configuration, meant to save conventional energy. The thermographic system used for the analysis covers the wavelength region 8-12 μm. The thermal images obtained showed that there are notable temperature differences on number PV panels, which may be attributed to material defects, manufacturing faults, module malfunction, and external abuse. © 2008 Materials Research Society.

Abstract: Corrosion of airport pavements is a major problem involved with materials engineering and transportation engineering. Airport pavements frequently start to deteriorate slowly primarily, gradually progressing to failure. Such failure can be expensive in terms of both money and lives, but can also be prevented. For that reason, intelligent techniques should be suggested, with the intention of examining the condition of such engineering structures. IR thermography and ground penetrating radar are two NDT (non-destructive testing) techniques that have the ability to inspect effectively substantial areas, such as airport pavements. In this work, two different airport pavements located at the International Airport of Athens, in Greece, were investigated by the use of the above two mentioned techniques. Successful detection of cracks, voids and other imperfections appearing either from the aging of the materials or due to poor workmanship was attained. Furthermore, this paper describes the problem of deteriorated airport pavements, shows the process and the apparatus used for the in situ tests, and finally presents results obtained from the investigations.

Abstract: In this work, infrared thermography (IRT) was used for the investigation of structural materials using the active approach. Four types of building materials were examined; three types of porous stone (from Rhodes, Cyprus, Rethymno - Crete) and one type of marble (Dionysus). Specimens containing self-induced defects of known dimensions and depths were studied. The samples were heated externally (thermal excitation) and thermograms were recorded continuously at the transient phase. Mathematical - thermal modelling enabling the modelling of the investigated subsurface defects, using the thermocalc 3-D software, was also implemented. Then, quantification analysis (i.e. temperature - time plots, as well as thermal contrast curves) from the experimental tests, as well as from the use of thermal modelling runs took place, indicating the thermal behaviour of building materials containing such defects. The results of this research show that IRT can be used for the detection and quantification of defects in structural materials.

Abstract: The preventive maintenance of rails is necessary for safe, successful and economical railway performance and operations. Rolling contact fatigue (RCF) is one of the main issues that concern the head of the railway. Progressively, RCF defects can propagate inside the material with the risk of damaging the rail, and thus they need to be monitored, categorized, evaluated, and treated through a comprehensive maintenance system. In a previous work with the Athens Metro, an innovative monitoring system was developed based on the capability of non-destructive techniques, such as IR thermography, to inspect and identify defects at early stages and reveal the activated paths of fracture (Moropoulou A., Avdelidis N., et al. Thermosense XXVII, 5782, 371-378, 2005). In the present work with the Athens Piraeus Electric Railways S.A. this system is further integrated into a complete system consisting of three components. The surveillance component identifies the rail defects and includes non-destructive techniques, such as visual inspection, infra-red thermography, ultrasonics, fiber optics microscopy, and ACFM. The data management component receives information from the various defect identification techniques, categorizes them and stores them for further use. The defect warning component uses risk indices such as defect level indices, defect extent indices, and risk threshold values, in order to evaluate the significance of the observed defects. All three components are part of a decision making system that monitors the development of defects, warns for significant threats and schedules rail maintenance.

Abstract: Rolling Contact Fatigue (RCF) is one of the main issues that concern, at least initially, the head of the railway; progressively they can be of very high importance as they can propagate inside the material with the risk of damaging the railway. In this work, two different non-destructive techniques, infrared thermography (IRT) and fibre optics microscopy (FOM), were used in the inspection of railways for the tracing of defects and deterioration signs. In the first instance, two different approaches (dynamic and pulsed thermography) were used, whilst in the case of FOM, microscopic characterisation of the railway heads and classification of the deterioration - damage on the railways according to the UIC (International Union of Railways) code, took place. Results from both techniques are presented and discussed.

Abstract: Eight syntheses of mortars used for restoration interventions in historic masonry were produced using the traditional materials of aerial lime and artificial pozzolanic additives. The mortars were aged over a 15-month period and then tested for properties related to chemical and mechanical stabilization using the following four analytical techniques: ultrasonic velocity propagation and the mortars' dynamic modulus of elasticity (Ed), mercury intrusion porosimetry for evaluation of microstructural characteristics (percentage open porosity, bulk density, average pore radius, total cumulative volume, and specific surface area), water capillary rise tests for the determination of total cumulative volume accessible to water and capillary rise coefficients of the mortars, and conventional mechanical tests for the determination of the mortars' ftexural and compressive strength. Performance is correlated to the mortars' chemical composition, microstructural characteristics (as measure by average pore radius) and mechanical characteristics as measured by dynamic modulus of elasticity (Ed) and ftexural and compressive strength (Fc). © 2005 Materials Research Society.

Abstract: Although, the efficiency of IRT (infrared thermography) as a NDT & E technique in the literature it is well documented, in the investigation of historic structures, where a restoration or conservation treatment can cause irreversible damage to the structure, it is considered to be of most importance. IRT is a non-destructive investigation technique that can be widely used due to the outstanding advantages that offers in a number of applications and specifically in the assessment of structural materials and techniques. In the present work, both IRT approaches, passive and active, were used, depending on the application, for the investigation of traditional-historical materials and structures. IRT was applied on restoration and traditional-historic materials and structures for the evaluation of conservation interventions (materials and techniques) concerning cleaning of architectural surfaces, restoration of masonries by repair mortars, as well as the disclosure of tesserae on plastered mosaic surfaces. For this reason, diagnostic studies on historical sites and structures took place. Wherever necessary, the emissivity values of the investigated materials were taken into account, after their determination in the laboratory on representative samples. Furthermore, in order to obtain useful information from the IRT surveys various properties (thermal, optical, physical) of the examined materials were taken into account. The outcome of this work provides strong evidence that IRT is an effective technique for the evaluation of historic buildings and sites.

Abstract: Thermal non-destructive approaches, passive and active, are widely used due to the outstanding advantages that offer in a number of applications and particularly for the assessment of materials and structures, hi this work, different applications, employing either MWIR or LWIR thermographic testing, as well as passive and/or active approaches, depending on the application, concerning the assessment of various materials are presented. In a few instances, thermal modelling is also discussed and compared with the outcome of experimental testing. The following applications are reviewed: Emissivity measurements. Moisture impact assessment in porous materials. Evaluation of conservation interventions, concerning: Consolidation interventions on porous stone. Cleaning of architectural surfaces. Assessment of airport pavements. Investigation of repaired aircraft panels. Through skin sensing assessment on aircraft composite structures. Real time monitoring of all features was obtained using passive imaging or transient thermographic analysis (active imaging). However, in the composite repairs and through skin imaging cases thermal modelling was also used with the intention of providing supplementary results, as well as to demonstrate the importance of thermal contact resistance between two surfaces (skin and strut in through skin sensing). Finally, in order to obtain useful information from the surveys, various properties (thermal, optical, physical) of the examined materials were taken into account.

Abstract: Two non-contact NDT & E (non-destructive testing and evaluation) techniques were employed in the inspection of quarry Pentelic marble samples; surface profilometry and infrared thermography. The samples were processed with different roughness treatments (i.e. 60, 80, 100, 220, 400 and 600 mesh) and were evaluated in the laboratory. Furthermore, different surface cleaning treatments were applied to a Pentelic marble surface in situ and then representative samples were collected and evaluated in the laboratory by the means of these two non-destructive techniques. Quantitative analysis of all samples was performed. In particular, the surface roughness parameter Rq at a specific length scale and 3-D micro-topography plots were attained by the use of the laser profilometry scanning approach, whilst temperature - time plots displaying the intensity of pixels as a function of time on the obtained thermal images were also obtained with the intention of distinguishing the influence of the applied roughness treatments. Results indicate that these two non-destructive techniques can be used for the assessment of surface roughness.

Abstract: Frequently, on outdoor thermographic surveys long wavelength infrared - thermal imaging systems are employed. When such systems are cooled, they are ideal for outdoor measurements, since they eliminate the effects of sunlight reflections and enhance the accuracy of the measurements. In this research study, long wavelength infrared thermography was used in the assessment of historic porous stones masonry, either consolidated or untreated, in the Medieval City of Rhodes, in Greece. Due to the difference between the thermal diffusivities of consolidated and untreated stones or even of moist and dry stones, infrared thermography was capable of imaging large areas, displaying qualitative variations in penetration depth (i.e. consolidation) and/or respiration behaviour (i.e. moisture impact), appearing as surface temperature fluctuations on the thermal image(s). The obtained thermal images provided significant information in the assessment of materials concerning moisture and consolidation treatments; monitoring of the physicochemical behaviour of porous materials. Conclusively, thermography ought to be considered as a powerful non-destructive assessment tool in the investigation of historic structures.

Abstract: Transient thermography was employed in the inspection of two repaired aircraft composite panels in the laboratory. The investigated panels were aluminium alloy panels under boron composite patching. The defects were placed between or under the plies of the composite patches and were assessed using firstly a simple heat excitation source with an IR camera and secondly an integrated pulsed thermographic system. In both situations, the defects were artificially created. After detecting the defects, the thermal images obtained from the transient thermographic inspection underwent an image processing quantitative analysis approach, in order for the qualitative images to be translated into quantitative results. Finally, mathematical - thermal modelling was also attempted in order to obtain information about the defects in space and in time.

Abstract: The study of the behavior of Byzantine buildings that have presented excellent behavior under earthquakes, such as Hagia Sophia in Istanbul, and the church of St. Michael in Kiev can become a valuable tool for the understanding of earthquake resistant construction techniques and materials. In this work, taking into account the historic Byzantine mortar nature and characteristics, several syntheses of repair mortars addressed to Byzantine masonries are produced and evaluated, aiming to consider the mechanical compatibility to historic ones and therefore to the monuments earthquake protection. Traditional materials (aerial lime, natural pozzolana, sand and brick fragments) are used for the mortar synthesis production, according to the data obtained by the characterization of historic mortars. The produced mortars were evaluated over periods of 3 and 6 months using mechanical tests (compressive, flexural) for the determination of mechanical strength and an ultrasonic technique for the determination of the dynamic modulus of elasticity. Furthermore, thermal analyses (DTA-TG) were performed for the chemical evolution evaluation of these composite systems in time. The obtained results indicate that the lime natural pozzolana mortar presented a sufficient mechanical behavior, analogous to historic mortars, while the lime presented the lowest ratio of f _c/f_f, that reveals an elastic behavior. All the examined mortars seem to be in progress after 6 months of curing, a fact that is confirmed by the rate of mechanical evolution and from Ca(OH)₂ conversion.

Abstract: Frequently, damages in porous materials arise as a direct or indirect consequence of moisture concentration and transport. Usually, detection of the existing moisture in porous materials is fundamentally necessary, in order to identify the actual damage, as well as their deterioration rate. There have been numerous reports about moisture detection in porous media, employing various direct techniques. In this research work, infrared thermography was employed with the intention of assessing moisture concentration in reference porous materials in the laboratory. Untreated and consolidated porous stones were subjected to capillary rise moisture tests, whilst infrared thermography was used for the monitoring of these laboratory tests. The performance of the investigated porous materials, in order to interpret the moisture phenomena studied and the obtained thermographs, was also examined in terms of their microstructure (mercury intrusion porosimetric results) and isothermic behavior (water sorption curves). The results of this work indicate that thermography ought to be considered as a nondestructive assessment tool for the detection of moisture in porous materials.

Abstract: Composite patching method is widely applied for repair cases of metallic aircraft structures due to more efficient performance than conventional repairs. However, the detection of structures integrity under patch, during the service life of aircraft, by non-destructive means is considered of great importance. In the present study, different NDT techniques such as active infrared thermography, eddy currents and electrical impedance spectroscopy, were applied for the detection of simulated artificially introduced damages - notches, on the surface of aluminum aircraft skin panels, Al 2024-T3, under composite patching (carbon reinforced laminates). The detection sensitivity of each technique was investigated based on the relation between thickness of composite patch and specific parameters of each method aiming at the development of a reliable, for this purpose, quality inspection technique.

Abstract: Emissivity can be defined as an expression that describes the optical properties of a material in sense of the extent of energy emitted with regard to an ideal black body. Since there is no infrared camera that can read temperature directly, correct emissivity values ought to be measured with the intention of interpreting thermal images obtained from thermographic surveys. In the present work, the emissivity values of numerous building and structural materials, such as stones, plasters, mortars, marbles and mosaics' tesserae, were calculated in accordance with the relevant ASTM standard approach or by the use of an empirical laboratory developed approach. The obtained emissivity values were discussed and explained in terms of the approach used, the wavelength effect, as well as the materials surface condition.

Abstract: In this work, pilot cleaning interventions applied by a wet micro-blasting method on architectural surfaces of three historic buildings in marble and porous stone were evaluated in situ and in the laboratory. The investigation was performed on characteristics stone surfaces (marbles and porous stone) of the following historic buildings: Athens, Academy and National Library of Greece in Athens center polluted urban environment and Bank of Greece in Piraeus marine environment. The materials of the facades were characterized, and the mechanism of decay was diagnosed. In addition, the cleaning method's efficiency was evaluated based on the acceptability of the alteration of the cleaned architectural surfaces. Criteria were both aesthetic and physico-chemical. In particular, the architectural surfaces were examined in situ by the means of fiber optic microscopy, infrared thermography and colorimetry. In the laboratory, methods of investigation were optical microscopy, X-ray diffraction, scanning electron microscopy with energy dispersion by X-ray analysis, mercury intrusion porosimetry, Fourier transform infrared spectroscopy, conductivity and pH measurements. The majority of measurements and analyses were applied before and after the pilot cleaning interventions. Finally, the results of this study contribute to the development of an integrated methodology for the assessment of cleaning interventions applied on architectural surfaces.

Abstract: Cement based mortars used for historic masonry restoration presented unsatisfactory results, due to their chemical and physico-mechanical incompatibility to original buildings. In the present research, several syntheses of restoration mortars are produced using traditional techniques and materials such as binders (aerial and natural hydraulic lime), pozzolanic additives (natural and artificial pozzolanas) and aggregates (sand and crushed brick). The technical characteristics of the mortars were determined using mechanical tests (compressive and flexural) and mercury intrusion porosimetry measurements at the time of 1, 3, 9, 15 months of curing. Water absorption measurements were performed at the time of 9 and 15 months curing, in order to evaluate mortars microstructural characteristics, their rate of water absorption and the total percentage of absorbed water. The aerial lime - artificial pozzolana mortar presented the best mechanical and microstructural performance. Hydraulic mortars acquired the maximum of the mechanical strength in 1 month, lime - pozzolana mortars in 3 months while aerial lime mortars continue to gain mechanical strength even in 15 months curing. Furthermore, the use of ceramic aggregates produces lightweight and elastic mortars, compatible to historic ones.

Abstract: In this paper, the example of the Materials Science and Engineering (MSE) Curriculum that exists as a scientific direction in the undergraduate programme of the Chemical Engineering School, in the National Technical University of Athens (NTUA), in Greece, is presented. The course content includes several tools, such as theoretical lessons, laboratory modules - non-destructive testing (NDT) and instrumental techniques - semi industrial scale devices, fieldworks and a dissertation thesis. The presented curriculum can be regarded as an innovative educational model for chemical engineering students that choose to become involved in the field of MSE. © 2003 Materials Research Society.

Abstract: The most reliable method to obtain correct emissivity values for the infrared thermographic systems and applications is to determine the emissivity of the targets to be tested. Although this approach is not possible during in situ applications, samples of the targets can be collected and measured, as in this work, in the laboratory. In the present work, the emissivity values of selected historic building materials were measured at a variety of temperatures, in the 3-5.4 μm and 8-12 μm regions of the infrared spectrum. Porous stones from the Mediterranean area and marbles, used as historic building materials, were investigated. The examined materials presented different emissivity values, caused by their surface state and microstructure. In addition, the effect of temperature and wavelength on the emissivity values of such historic building materials was also considered.

Abstract: In this work, infrared thermography is used for detecting the movement of water - moisture in various porous materials in the laboratory, with the intention of validating the examination of real scale material systems in situ. Different materials have been subjected to capillary rise tests and to cycles of evaporation with water under controlled environmental conditions (Relative Humidity & Temperature). Material samples of a reference porous stone, of three basic categories of repair mortars, of consolidated porous stones and of simulating prototype porous materials were examined in lab. Furthermore, systems like historic masonries, were examined in situ, more specifically the Venetian Fortifications in Heraklion, Crete and the Medieval Fortifications in Rhodes, undergoing severe alveolation in the aggressive marine atmosphere of the Aegean. Infrared thermography has been shown to be an effective technique for verifying relations between moisture and environmental conditions. Hence, infrared thermography can be used as an evaluation tool for studying the movement of water through porous materials - water absorption and evaporation.

Abstract: An experimental investigation was conducted for the determination of defects at aircraft components and for the composite patches evaluation. Cracked aluminum panels, untreated and repaired with carbon and boron composite patches, were inspected. The non-destructive techniques used in the assessment of these aircraft materials were infrared thermography and fiber optics microscopy. Infrared thermography is used for the localization of defects on aluminum panels, as well as on repaired ones with composite patches. Furthermore, the detection of defects on repaired aluminum panels that have undergone to fatigue testing, is attempted. Fiber optics microscopy is employed in order to examine the surface morphology of both carbon and boron composite patches. The results of this laboratory research work can lead to the development of an integrated non-destructive method for in field inspections of aircraft components.

Abstract: Corrosion of asphalt pavements is a major problem involved with materials engineering and transportation engineering. Asphalt pavements frequently start to deteriorate slowly primarily, gradually progressing to failure. Such failure can be expensive in terms of both money and lives, but can also be prevented. For that reason, intelligent techniques should be suggested, with the intention of examining the condition of such engineering structures. IR thermography is a non-destructive technique that has the ability to inspect effectively substantial areas, such as airport pavements. It has been used successfully in the detection of cracks, voids and other imperfections appearing either from the aging of the materials or due to poor workmanship. Investigation of asphalt overlays by the means of IR thermography is possible, given that subsurface defects in a material influence the heat flow through that material, generating surface temperature alterations. Despite that, other issues such as, environmental conditions and surface temperatures should also be considered, in an attempt to obtain reliable results. In this research work, a selection of asphalt pavements located at the International Airport of Athens, in Greece, are investigated by the use of scanning IR thermography. In conclusion, this paper describes the problem of deteriorated airport pavements, the process and the apparatus used for the in situ tests, whilst the results obtained lead to the suggestion of a predictive monitoring non-destructive technique for the inspection and appropriateness of airport pavements.

Abstract: In this research work, an experimental investigation was performed for the determination of defects on aircraft materials. Infrared thermographic active approach was used for the location and identification of defects on cracked aluminum panels untreated and repaired with carbon or boron epoxy composite patches. Furthermore, the quantification of these detected defects was attempted, using selected image processing and analysis techniques. Thermographic image analysis using histograms and digital image processing were applied on these obtained thermal images with the intention of calculating the localized defected areas. The results from these image analysis techniques were compared and discussed in terms of developing an integrated approach for the quantification of defects on aircraft components.

Abstract: In this work, infrared thermography was applied and investigated as a non-destructive tool in the assessment of materials and techniques for the protection of cultural heritage. Diagnostic studies on monuments and historic buildings, situated in Greece, were performed. Long wave infrared thermography was used on restoration and traditional-historic materials concerning architectural surfaces and historic structures for research purposes such as: The assessment of moisture impact to porous stone masonries and the evaluation of conservation interventions (materials and techniques) regarding, consolidation interventions on porous stone masonries, restoration of masonries by repair mortars, and cleaning of facades. The results of this work indicate that thermography can be considered as a powerful diagnostic nondestructive tool for the preservation and protection of cultural heritage.

Abstract: The deterioration of asphalt pavements and airport runways is one of the most serious problems concerned with materials engineering, transport engineering and transportation in general. Usually, this is due to the lack of knowledge or even to the lack of commitment, for maintaining such structures. When failure occurs in an airport runway or in an asphalt pavement, reconstruction is expensive. Therefore, cost-effective ways must be suggested, in order to see how badly deteriorated the investigated structure is. One of these cost-effective ways is the infrared thermography technique. This technique is used successfully in the detection of cracks, surface voids and other anomalies appearing from the ageing of such materials. In this research work, by using an infrared thermographic system (AVIO TVS 2000 Mk II LW, wavelength 8-12 μm), and with the aid of liquid diffusion, an investigation of asphalt pavements and airport runways situated in Greece was performed. The results of this investigation have led to the design of a monitoring and control NDT system for the inspection of the defected areas of the airport runways and asphalt pavements and consequently the appropriateness of distinctive engineering structures.

Abstract: Infrared thermography is a non-destructive investigation technique, which is largely used because of the outstanding advantages that it is capable to provide in a variety of applications and especially for conservation purposes of historic monuments, where destructive sectioning is prohibited. In the present work, dual band infrared thermography (3-5.4 μm and 8-12 μm) is used, to evaluate the humidity distribution by capillary rise in reference samples of porous materials in lab, in order to validate the examination of real scale material systems in situ. The combined study of vapor/moisture transport in prototypes simulating porous materials under controlled environmental conditions (Relative Humidity 60-80% & Temperature 25-40°C), provides interpretation tools to the investigation by IR Thermography of transport phenomena occurring at the masonry. The cross-investigation of consolidated porous stones and of repair mortars, in lab and in situ on historic monuments in Greece, permits to evaluate the performance of conservation materials, regarding their compatibility to the porous building stones on historic masonries. It is deduced that Infrared Thermography by recording thermal maps of the real surfaces under study provides information on the differential behavior of the various materials on the masonry scale regarding the water impregnation and evaporation phenomena, which control the weathering effects in porous media. Hence, infrared thermography might be used as a non-destructive technique to evaluate on a micro and macro scale the performance of conservation interventions and materials, in compatibility to the original materials on the level of the structures.

Abstract: Several non destructive techniques are recently applied to assess and evaluate weathering damages. In the present work several macro- and micro- non destructive tests, have been employed, in the Fortress of the Medieval City of Rhodes, for the examination of the weathering: Digital Image Processing for the mapping of the decay patterns, Fibre Optics Microscopy for the examination of the morphological characteristics of the surface, and Infra Red Thermography for the assessment of the humidity distribution within the masonries and the degradation of the stone texture. The results of the above methods are supported by porosity and humidity measurements regarding the evaluation of the microstructural characteristics of the stone and the water percolation within the masonry. It is proved that these three methods can be combined into a reliable assessment tool concerning environmental impact on architectural surfaces and particularly in the form of a thorough characterization of the materials degradation.

Abstract: The chemical and mechanical properties of mortars and bricks were studied using X-ray diffraction, scanning electron microscopy, differential thermal analysis and transmission electron microscopy to prove that the earthquake worthiness of Hagia sophia is strongly dependent on the properties of mortars and bricks used in its masonry. The mortars showed considerable mechanical strength along with longevity. It showed strong resistance to the environmental pollution and to the presence of salt, while the gel phase as binder allowed for greater energy absorption and the compatibility of the mortar to the original ones allowed continuous stresses and strains.

Abstract: In the present work, the main decay phenomena of the various lithotypes of the ancient Sanctuary of Demeter (1600BC) in Eleusis-Greece are studied in respect of the environmental factors under monitoring, concerning an area characterised by a heavy industrial pollution in an intense marine environment. Stone surface alterations are studied by examining the various neoformations. Specific investigation has been performed on the depositions of the total suspended particles, mainly characterising the polluted atmosphere in the Thriassian plain, as possible weathering causes. OM, SEM, EDX and XRD analysis are employed consequently. Decay phenomena like crust formations (gypsum, loose depositions of soot and suspended particles, at the more or less sheltered areas), various cementitious encrustations on the marble surfaces, especially the horizontal ones, or Fe-rich yellow patinas on the washed out surfaces are evidenced. These weathering phenomena might be attributed to pollutants, suspended particles and their wet and dry depositions, which are measured according to the analysis performed. Moreover, the newly evidenced decay pattern of 'cementitious encrustations' (rich in Ca-Si-Al complexes, which characterises the flying ash coming from the nearby cement industry) and its hydration products, may be attributed to a 'cement coating' that exerts pressures to the marble surface and triggers pitting phenomena. Hence, preservation policy planning should recall for an appropriate management of the emission sources.

Abstract: In the present study the possible chemical interactions among the constituents of historical walls have been investigated. In Venice but also in the whole Mediterranean area the 'cocciopesto' (constituted of powder and brick fragments which traditionally confer hydraulic properties to the mortar) has been widely employed both for mortars and the so called 'marmorino' plasters. The work has been developed by examining the brick-mortar interaction on historical buildings in Venice. The samples were chemically analysed through XPS and XPS-Imaging techniques in order to ascertain the chemical composition of the interface layers. The results clearly indicate that a true chemico-physical interaction between brick and lime is present in the historical materials. A calcium carbonate accumulation has been observed at the brick-mortar interface.

Abstract: The original mortars, which have been deteriorated by natural weathering, salt decay and the corrosive action of polluted atmospheres, have to be replaced. However, the uncontrolled and rather extensive use of cement and polymer-based mortars, give very unsatisfactory results, due to the high content of soluble salts and the limited compatibility with the original components of the masonry. Hence, restoration mortars compatible with the traditional building materials, though more resistant than the original ones, should be searched out. In the present work an attempt is made to evaluate whether the traditional materials and technologies, reproduced by the monks of the Toplou Monastery in Crete, do provide ameliorated restoration mortars. Physical, chemical and mineralogical investigations on Byzantine and post - Byzantine mortars and plasters of crushed brick and lime from Rhodes, Crete and Hagia Sophia, by Optical Microscopy, X-Ray Diffraction Analysis, Thermogravimetric Analysis, Hg- Porosimetry and Infra Red Spectroscopy, seem to provide reliable evaluation criteria. This comparative study leads to the conclusion that the proper mixture ratio, the appropriate lime technology and raw materials, the crushed brick granulometry and texture, as well as the proper application techniques are necessary to achieve an optimized approach to the traditional mortars.

Abstract: In the present study several cleaning procedures were taken into account: microblasting, ammonium carbonate, EDTA, etc. The various cleaning procedures were applied to Venetian Istria stone manufacture. The performance evaluation of the various procedures employed was accomplished by measuring the following significant parameters, before and after treatment: colour change through the CIELab method, surface morphology through a fiber optical microscope (MFO) and analysis of the different chemical action of the employed procedures.

Abstract: The decay processes in monuments, considered as interaction between building materials and environmental factors, presents a specific interest in the case of marine environment (Mediterranean), in mild climatic conditions. An extended monument, like the Medieval Fortress of Rhodes could be a characteristic example. It is constructed by a susceptible to salt decay biocalcareous porous stone which suffers mainly from salt crystallisation and hard carbonate crusts formation. The research program has been developed on walls of different typologies, according to their position and exposure orientation to various environmental factors, and specifically concerning humidity sources as capillary rise via ground and marine salt spray. Stone samples from different positions along the fortress, at various heights and depths on the walls, significant of the main decay patterns (alveolar, carbonate crust and mixed), underwent physical and chemical examination. Humidity and soluble salts' concentration measurements by Atomic Absorption Spectroscopy, Ionic Chromatography and specific conductivity allow the assessment of their distribution patterns on the masonries. Hence from the correlation between environmental factors and the material properties, directions for a conservation plan might be derived.

Abstract: The deterioration of asphalt pavements and airport runways is one of the most serious problems concerned with materials engineering, transport engineering and transportation in general. Usually, this is due to the lack of knowledge or even to the lack of commitment, for maintaining such structures. When failure occurs in an airport runway or in an asphalt pavement, reconstruction is expensive. Therefore, cost-effective ways must be suggested, in order to see how badly deteriorated the investigated structure is. One of these cost-effective ways is the infrared thermography technique. This technique is used successfully in the detection of cracks, surface voids and other anomalies appearing from the ageing of such materials. In this research work, by using an infrared thermographic system (AVIO TVS 2000 Mk II LW, wavelength 8-12 m), and with the aid of liquid diffusion, an investigation of asphalt pavements and airport runways situated in Greece was performed. The results of this investigation have led to the design of a monitoring and control NDT system for the inspection and the appropriateness of smart engineering structures.

Abstract: In order to plan the preservation of historic complexes, in situ monitoring and control techniques of Environmental Impact Assessment have to be employed and spatial management of information has to be performed. In the present work a pilot application is demonstrated on the historic complex of the Medieval City of Rhodes suffering from the percolation of soluble salt solutions and the crystallization of salts within the porous historic masonries. The results of Non Destructive Methods, and more specifically Infrared Thermography, for the assessment of the humidity distribution within the masonries and the degradation of the stone texture, are supported by the examination of the microstructural characteristics of the stone and the water percolation within the masonry, regarding soluble salts and humidity measurements. It is proved that these methods can be combined into a reliable assessment of the critical levels of environmental factors triggering damage to the monument. A G.I.S (Geographic Information System), could be used to manage a multidisciplinary database, including environmental, functional, materials, structural and social data. Integrated environmental planning can be achieved by the analysis of all the relevant data with the objective of eliminating the negative impact of the natural and man-made environment on the monumental building and the historical complexes as a whole, in order to prevent further damage and to maintain the necessary conservation level, while the historic site and city or complex is revitalised through new uses and its role is strengthened. Integrated management is suggested in terms of: preservation of historic cities as intervention to materials and structures, urban planning and environmental management to eliminate environmental loads for a sustainable historic city, development and rehabilitation of the city places and buildings by the introduction of new uses (cultural and recreational activities and tourism).