Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou - NTUA – National Technical University of Athen...
Prof. Antonia Moropoulou - NTUA – National Technical University of Athens  Copyright  ©ELAICH Beneficiaries 2009-2012 This...
Prof. Antonia Moropoulou - NTUA – National Technical University of Athens  Abstract The current presentation examines the ...
Prof. Antonia Moropoulou - NTUA – National Technical University of Athens  Content Educational Linkage Approach In Cultura...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Mineral : Natural, hom...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Granite  (upper: photo...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Igneous rocks Basalt: ...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Process of formation o...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Sedimentary rocks Lime...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Metamorphic rocks Marb...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Metamorphic rocks - Re...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Metamorphic rocks - Re...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Stone properties Poros...
PROPERTIES OF STONES <ul><li>Porosity </li></ul><ul><li>Density </li></ul><ul><li>Sorptivity </li></ul><ul><li>Mechanical ...
<ul><li>Porosity may exist in  igneous rocks  for various reasons:  </li></ul><ul><li>Gas dissolved in the magma that is r...
Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Educational Linkage Approac...
<ul><li>True density :  The ratio of the mass (m) of a sample over its true volume (V s )   i.e. without empty spaces </li...
Sorptivity The  sorptivity  is a measure of the rate at which a liquid rises into a porous body.  Capillary pressure draws...
Sorptivity One normally measures the increase in weight as liquid enters a stone, rather than directly measuring the heigh...
Mechanical Properties The most important property for a building material, from the point of the engineer, is the compress...
Mechanical Properties Educational Linkage Approach In Cultural Heritage   When a solid object is subjected to tensile stre...
Hardness Mohs' scale of mineral hardness  quantifies the scratch resistance of minerals by comparing the ability of a hard...
Coefficient of thermal expansion Educational Linkage Approach In Cultural Heritage   Prof. Antonia Moropoulou – Topic 2 .5...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Stone properties Prof....
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Decay of stones Prof. ...
Educational Linkage Approach In Cultural Heritage   2. 5 .1. Historic building materials  -  Stones Decay of stones Prof. ...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Prof. Antonia Moropo...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Ceramics are defined...
Educational Linkage Approach In Cultural Heritage   Prof. Antonia Moropoulou – Topic 3.6: Diagnosis of decay: Mechanisms, ...
Educational Linkage Approach In Cultural Heritage   Prof. Antonia Moropoulou – Topic 3.6: Diagnosis of decay: Mechanisms, ...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Forming of ceramics ...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Drying of ceramics D...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Sintering of ceramic...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Characterization of ...
Educational Linkage Approach In Cultural Heritage   2. 5 .2. Historic building materials  -  Ceramics Thermal Analysis as ...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Mortars - Components ...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Characterization of m...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Characterization of m...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Typical lime mortars ...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Hydraulic lime mortar...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Prof. Antonia Moropou...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Crushed brick lime mo...
Educational Linkage Approach In Cultural Heritage   2. 5 .3. Historic building materials  -  Mortars Prof. Antonia Moropou...
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Historic building materials: Stones, ceramics, mortars

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Elaich module 2 topic 2.5 - Historic building materials

  1. 1. Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Knowing the built heritage Module 2 Basic Cour s e Teaching Material Topic 2 .5 Historic building materials: Stones, ceramics, mortars Educational Toolkit
  2. 2. Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Copyright ©ELAICH Beneficiaries 2009-2012 This material is an integral part of the “ELAICH – educational toolkit” and developed as part of the project ELAICH – Educational Linkage Approach in Cultural Heritage within the framework of EuroMed Cultural Heritage 4 Programme under grant agreement ENPI 150583. All rights reserved to the ELAICH Beneficiaries.   This material, in its entirety only, may be used in &quot;fair use&quot; only as part of the ELAICH – educational toolkit for the educational purposes by non-profit educational establishments or in self-education, by any means at all times and on any downloads, copies and or, adaptations, clearly indicating “©ELAICH Beneficiaries 2009-2011” and making reference to these terms.   Use of the material amounting to a distortion or mutilation of the material or is otherwise prejudicial to the honor or reputation of ELAICH Beneficiaries 2009-2011 is forbidden.   Use of parts of the material is strictly forbidden. No part of this material may be: (1) used other than intended (2) copied, reproduced or distributed in any physical or electronic form (3) reproduced in any publication of any kind (4) used as part of any other teaching material in any framework; unless prior written permission of the ELAICH Beneficiaries has been obtained. Disclaimer This document has been produced with the financial assistance of the European Union. The contents of this document are the sole responsibility of the ELAICH Consortium and can under no circumstances be regarded as reflecting the position of the European Union. Educational Linkage Approach In Cultural Heritage
  3. 3. Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Abstract The current presentation examines the basic categories of the historic building materials used for the construction of monuments throughout the centuries. It examines their evolution and their selection criteria. The main categories, stones, ceramics and mortars are then described in detail, regarding their provenance, manufacturing-forming, basic properties and characterisation Educational Linkage Approach In Cultural Heritage
  4. 4. Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Content Educational Linkage Approach In Cultural Heritage Table of contents of this presentation Historic materials 2.5.1 Stones 2.5.2 Ceramics 2.5.3 Mortars
  5. 5. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Mineral : Natural, homogeneous solid material that forms usually through inorganic procedures Rock : The material of the solid layer of earth, which is a product of geological actions. It consists of minerals that influence the physicochemical properties of the rock Stone : A rock that has been treated and formed into shape by hand or mechanical means Rock Categories based on their geological formation path Igneous : They are formed when molten magma cools Sedimentary : They are made by deposition of either clastic sediments, organic matter, or chemical precipitates followed by compaction of the particulate matter and cementation during diagenesis Metamorphic : are formed by subjecting any rock type to different temperature and pressure conditions than those in which the original rock was formed. Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  6. 6. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Granite (upper: photograph, below: polarized microscopy). Plutonic rock with holocrystalline matrix, leucocratic, acidic. It contains alkali feldspars, biotite and/or muscovite (micas) and plagioclase Igneous rocks Santiago di Compostela, Spain (built mostly with granite) Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  7. 7. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Igneous rocks Basalt: The extrusive rock of gabbro. It is melanocratic with a glassy or crystalline matrix. The crystals are mainly basic feldspars, augite, diopside or olivine (Below polarized microscopy image) Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  8. 8. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Process of formation of sedimentary rocks Conglomerate : is a clastic sedimentary rock that contains large (greater than 2mm diameter) rounded clasts. The space between the clasts is generally filled with smaller particles and/or a chemical cement that binds the rock together Medieval City of Rhodes: Fossiliferous calcareous highly porous stone, where microcrystalline calcitic binder is embedded by calcareous aggregates Sedimentary rocks Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Scanning Electron Microscopy
  9. 9. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Sedimentary rocks Limestone: is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO 3 ). Like most other sedimentary rocks, limestones are composed of grains, however, around 80-90% of limestone grains are skeletal fragments of marine organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. Some limestones are formed completely by the chemical precipitation of calcite or aragonite. i.e. travertine . Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Photos courtesy of Museum of Archaeology & Art History – University of Athens Fossiliferous limestone Fossiliferous Sandstone Shelly limestone Limestone of Attica
  10. 10. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Metamorphic rocks Marble: A metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO 3 ). It has a hardness 3 Mohs and specific gravity 2,7 g/cm 3 . It is very durable against decay factors due to its microstructure. However, it can be damaged by fire since at 900 ο C, it decomposes calcium carbonate (CaCO 3 ) into CaO and CO 2 . Color is white, grey, pink or green with various veins Pentelic marble, Acropolis of Athens Photo courtesy of A. Moropoulou ELAICH Athens Experimental Course Acropolis of Athens, Parthenon marbles Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  11. 11. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Metamorphic rocks - Representative Greek Marbles Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Photos courtesy of Museum of Archaeology & Art History – University of Athens Marble from Penteli Marble from Naxos Marble from Skyros Marble from Evia
  12. 12. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Metamorphic rocks - Representative Greek Marbles Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Photos courtesy of Museum of Archaeology & Art History – University of Athens Marble from Arcadia Marble from Eretria Marble from Volos Marble from Thasos
  13. 13. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Stone properties Porosity Porosity and pore size distribution play an important role as they directly influence the fluid flow through the stone. Decay phenomena such as soluble salts efflorescence and subefflorence, freeze-thaw decay and biological decay are highly dependent on the stone’s porous network. Density Density, and in particular apparent density, is a good indicator of a stone’s decay status. It can decrease if cracks and microcracks are developing, or it can increase if the porous network is filled with salts. In both cases, this has detrimental effects on the mechanical properties of the stone Water absorption It controls the water transport phenomena and thus all the decay mechanisms associated with the presence of water (salt decay, biological decay, freeze-thaw decay) Hardness It is important in application where wear resistance is required as the primary function of the stone (e.g. floors) Thermal expansion coefficient Very important property especially at climates that demonstrate high temperature fluctuations. A large thermal expansion coefficient can result in mechanical stresses in the structure if the stone is not allowed to expand or contract freely. Structures are more susceptible to failure when building materials of very different thermal expansion coefficient are combined, as this can lead to differential mechanical stresses Mechanical properties The mechanical properties of interest are compression strength (since building stones are usually placed such that they are subjected to compression stresses) and the modulus of elasticity Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  14. 14. PROPERTIES OF STONES <ul><li>Porosity </li></ul><ul><li>Density </li></ul><ul><li>Sorptivity </li></ul><ul><li>Mechanical properties </li></ul><ul><li>Hardnes </li></ul><ul><li>Coefficient of thermal expansion </li></ul>Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  15. 15. <ul><li>Porosity may exist in igneous rocks for various reasons: </li></ul><ul><li>Gas dissolved in the magma that is released during crystallization, which then becomes trapped in pockets between the mineral grains in the rock. These pores are most often closed, that is, fluids cannot enter them from the surface of the stone </li></ul>Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Educational Linkage Approach In Cultural Heritage Porosity In sedimentary rocks , the pores are created when the particles of sediment pack together. The amount of porosity in the final rock depends on the amount of cementing material that is deposited. As the cement has to move through the open pores, it is unlikely to obtain a structure with completely closed pores. Typically, sedimentary rocks have interconnected pores Metamorphism will usually reduce the porosity of the stone, due to the high pressures involved . The size of the pores might simply be reduced, or some pore collapse might occur. In such a case, the interconnected pores might be disrupted, and converted to isolated pockets <ul><li>The rock might originally contain relatively soluble grains that are dissolved by weathering, so that a network of pores is created when they are removed </li></ul><ul><li>As the rock cools the grains of different minerals may contract by different amounts, leading to cracking between the grains </li></ul>
  16. 16. Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Educational Linkage Approach In Cultural Heritage Porosity The porosity P of a porous medium (such as a rock or a sediment) describes the fraction of void space in the material , where the void (pore) may contain, for example, air or water. It is defined by the ratio: where V P is the volume of pores (void-space) and V is the total or bulk volume of material, including the solid and void components, and V s is the volume of the solid phase <ul><li>Porosity is defined as: </li></ul><ul><li>Total porosity : refers to all pores (in this case V p refers to all pores) </li></ul><ul><li>open or active porosity : refers to those pores that allow the transfer – flow of water (in this case V p refers to those pores that are accessible, i.e. the open pores </li></ul>
  17. 17. <ul><li>True density : The ratio of the mass (m) of a sample over its true volume (V s ) i.e. without empty spaces </li></ul>Educational Linkage Approach In Cultural Heritage Density The density ρ of a porous medium (such as a rock or a sediment) is the ratio of the mass (m) of a body to its volume (V) : There are two types of density to distinguish: the density of the minerals that constitute the rock, and the bulk density of the rock that includes a mixture of minerals plus porosity. The difference between them has to do with whether we include the volume of the pores in V Apparent density : The ratio of the mass (m) of a stone sample over its apparent volume (V) i.e. including empty spaces Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  18. 18. Sorptivity The sorptivity is a measure of the rate at which a liquid rises into a porous body. Capillary pressure draws the liquid into the pores , just as it draws water into a capillary tube. The smaller the pores, the higher the liquid will rise . The maximum height H e that a liquid will rise in a capillary depends on the density of the liguid, ρ , the gravitational constant, g = 9.8 m 2 /s , the liquid/vapor surface tension (interfacial energy), σ LV , of the liquid, the contact angle (angle made by the surface of the liquid where it makes contact with the wall of the capillary), θ , and the radius of the tube: For water: σ LV = 0.072 Joules/m 2 θ ≈ 0 -> cos( θ ) ≈ 1 ρ = 1000 kg/m 3 The rate of humidity rise can be described by a first order kinetic model*, where H is the height at time t , H e is the equilibrium height and t cr is a time constant, and H 0 is a correction factor that relates to the humidity portion that is confined in the stone pores and cannot be removed by drying *M. Karoglou, A. Moropoulou, A. Giakoumaki, M.K. Krokida “ Capillary rise kinetics of some building materials ” J of Colloid and Interface Science , 284 [1] 260-264 2005 Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  19. 19. Sorptivity One normally measures the increase in weight as liquid enters a stone, rather than directly measuring the height of rise. Suppose a stone sample with a bottom area A is placed in contact with water. The amount of water adsorbed, Δ W depends on the contact area and time Sorptivity is then defined as follows It depends : - From the porosity : More porous stones absorb more water - From the shape and size of the pores : Pores that are large and rather straight, allow the easy entrance of water. In contrast, pores of small diameter and with complex shapes and interconnections as well as closed pores (that do not connect between each other) makes wetting of stone more difficult Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  20. 20. Mechanical Properties The most important property for a building material, from the point of the engineer, is the compressive strength, because the material must support the weight of the building. Brittle materials are weaker in tension (i.e., when they are pulled apart) than in compression (i.e., when they are crushed). This is true because tension pulls the flaws open, whereas compression tends to close them. When salt crystals grow inside a stone, they push on the pore walls and create tensile stress. Therefore, in evaluating durability, we are most interested in the tensile strength of stone. This is measured by the Brazilian test, or splitting test, which uses a cylindrical specimen (d) and applies a force along its length (L) . The tensile strength is then given by: σ t = 2F/( π L d) The compressive strength , σ c is typically measured by squeezing a cylinder or cube of material between the jaws of a testing machine . Regardless of the shape of the sample, the strength is given by the force, F, at which the fracture occurs, divided by the area, A , of the surface on which the force is applied: σ c = F/A Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars
  21. 21. Mechanical Properties Educational Linkage Approach In Cultural Heritage When a solid object is subjected to tensile stress, its length increases from L to L + DL. The fractional change in length is called the strain , ε The ratio between the stress, σ = F/A, and the strain is called the elastic modulus (or, Young's modulus), and is usually denoted by E: Rather than stressing a material to measure its modulus, the elastic modulus can be found from the velocity of sound waves passing through it. The elastic modulus can be calculated from the bulk density, d b , and the pulse velocity, v: Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Material Elastic Modulus (GPa) Steel 200 Window Glass 60-70 Marble 30-70 Limestone 10-50 Concrete 15-25
  22. 22. Hardness Mohs' scale of mineral hardness quantifies the scratch resistance of minerals by comparing the ability of a harder material to scratch a softer material. With the Mohs Scale, the hardness of a material is measured against the scale by finding the hardest material that it can scratch, and/or by identifying the softest material that can scratch it. If a given material can be scratched by topaz, but not by quartz, its hardness on Mohs scale is 7.5. Note: The table above shows a comparison with absolute hardness measures using a sclerometer. The Mohs scale is a ordinal or successive scale and therefore, does not measure or compare actual hardness. For instance, corundum is twice as hard as topaz, but diamond is almost four times as hard as corundum yet there is only one step between each of these three minerals Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Rock Hardness Mohs scale Granite, Gneiss 5,5-7,5 Basalt 4,5-6,6 Argillaceous schist 1,5-3,5 Psammite 1,5-7,5 Limestone, marble 2,5-3,5 Dolomite 2,5-4,5 Phyllite 2,5-5,5 Quarzite 6,5-7,5
  23. 23. Coefficient of thermal expansion Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials: Stones, Ceramics, Mortars Materials expand because an increase in temperature leads to greater thermal vibration of the atoms in a material, and hence to an increase in the average separation distance of adjacent atoms. The linear coefficient of thermal expansion α describes by how much a material will expand for each degree of temperature increase, as given by the formula: where: dl is the change in length of material in the direction being measured l is the overall length of material in the direction being measured dT is the change in temperature over which dl is measured
  24. 24. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Stone properties Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  25. 25. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Decay of stones Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Metamoprhic rock (marble) Archaeological site of Eleusis Mechanism of alveolation P. Theoulakis, A. Moropoulou “Salt crystal growth as weathering mechanism of porous stone on historic masonry”, J. Porous Materials, 6 (1999) pp. 345-358 Black crust It is the result of gypsum formation in the calcite surface and of the absorption of black smoke particles, Η/C and other particles of atmospheric origin that act as active catalysts in the transformation of calcite into gypsum. Its surfaces are protected from direct washout from rain water Salt crystallization It refers to the mechanical decay of porous stones, through the development of mechanical tensions in the interior of the stones (pores) from salt crystals and disruption of the material when these tensions surpass its strength. The main salt sources in masonries are rising damp (from the ground), neighboring materials, such as cement and usually the binding mortar itself. If the evaporation takes place in the interior of the mass of the material, the decay appears in the form of alveolation) Sedimentary rock (biocalcarenite) Medieval City of Rhodes Photo courtesy of A. Moropoulou
  26. 26. Educational Linkage Approach In Cultural Heritage 2. 5 .1. Historic building materials - Stones Decay of stones Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Gypsum formation The continuous peeling of the weathered surface reveals fresh material that in turn, is exposed to the creation of gypsum layer reaction and subsequent peeling, with the result that the phenomenon develops in depth The deterioration of the gypsum layer at the surface of the pentelic marble removes the details from the face and body of the Caryatides statues. In order to avoid further deterioration, for their protection, the Caryatides were placed in the Acropolis Museum. Replicas replaced the original ones at the Erectheion. Metamoprhic rock (marble) Detail of the Parhenon frieze Photo courtesy of K. Labropoulos See Module 3 – Topic 3.4 Phenomena and mechanisms of decay Prof. A. Moropoulou, NTUA For more information: The decay patterns of building stones are governed by their composition, microstructure, physicochemical and physicomechanical properties
  27. 27. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials As described in topic 2.1 the use of ceramics as building materials date back to the neolithic period when mud brick houses started appearing that were coated with plaster. Since then, ceramics have been used as the main building material of many civilizations, even when other building materials (e.g. stones) where used as the building material of choice for structures of capital importance (e.g. temples). The Romans in particular, followed by the Byzantines, used fired bricks as their main building element in their architecture. The use of ceramic bricks has decreased with the introduction of more modern materials such as steel and Portland cement both of which, however, do not exhibit the durability that the historic ceramic material has demonstrated in the span of centuries. Unfortunately, the shift to more modern materials has resulted in much of the manufacturing technology and especially the compositions of the traditional ceramics being lost. Today, significant efforts are focusing on reverse engineering these materials, either in order to manufacture ceramics compatible with the traditional ones, or in order to improve and impart greater durability to ceramic materials for modern applications. Sustainability and the concept of “green building” has revived the interest in the historic ceramic technology
  28. 28. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Ceramics are defined as non metallic inorganic solids with crystalline or amorphous structure . They are usually, tough, brittle, with a high melting point , with low electrical and thermal conductivity, with good thermal stability and with high compression strengths <ul><li>Classic ( natural ) : They are made from natural materials, usually from clay-earth, lime and sand. They are used for pottery, kiln bricks, tiles, glass and cement </li></ul><ul><li>Technical : They are made since 1900 with various properties (high strength, electronic applications, biological applications, insulation, resistances, semi-conductors ) </li></ul>Advantages of technical ceramic materials The structural ceramics offer certain advantages over the natural structural materials: Generally, they are lighter from equivalent size structural stones. It is possibly to obtain ceramic structural units of any shape and size, since the ceramic material are typically processed in a fluid state, thus, through the use of molds they can be formed accordingly Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  29. 29. Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 3.6: Diagnosis of decay: Mechanisms, criteria and techniques Moropoulou, A., Cakmak, A.S., Polykreti, K., “ Provenance and technology investigations of the Agia Sophia bricks ” , J. American Ceramic Society, 85 [2] (2002) pp. 366-372 The possibility the bricks from the dome of Hagia Sophia originating from Rhodes is up to 97% compared with the raw materials of ceramics used in other Byzantine Monuments of Istanbul Description of the sampled bricks and tiles The Great Basilica of Hagia Sophia (532–537 A.D.) is famous for its architectural and artistic magnificence. According to Diegesis (Narration), a 9th century text, the great dome was constructed with specially ordered brick from Rhodes: “. . . Special light bricks have been ordered from the island of Rhodes, weighing one-twelfth the weight of normal brick, to use them for building the four main arches and the dome. The structure is thus completed. . . . ” After a strong earthquake in 557 A.D., the great dome collapsed and was rebuilt with lightweight bricks from Rhodes Within the framework of a trilateral protocol agreement among Princeton University, Bogazici University, and the National Technical University of Athens concerning the structure and materials of Hagia Sophia and other monuments of historic significance in Byzantine Istanbul provenance and technology investigations of the Hagia Sophia bricks were performed. Sample bricks were studied from Hagia Sophia, from Byzantine monuments in Istanbul, and from a 6 th century Basilica in Rhodes The Hagia Sophia Bricks Lightweight - High Strength - Microporous bricks Neutron Activation Analysis combined with multivariate statistics allow the calculation of probabilities of Hagia Sophia samples belonging to the Istanbul or Rhodes groups
  30. 30. Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou – Topic 3.6: Diagnosis of decay: Mechanisms, criteria and techniques Moropoulou, A., Cakmak, A.S., Polykreti, K., “ Provenance and technology investigations of the Agia Sophia bricks ” , J. American Ceramic Society, 85 [2] (2002) pp. 366-372 This reveals the existence of organized workshops, with mass production and a level of experience and know-how sufficient to satisfy the demand for standardized product quality. Πεσσοί : Λαξευτοί λίθοι Τοιχοποιία Θολοδομία Συμπαγείς πλίνθοι, Ισχυρά, υδραυλικά κονιάματα με κεραμικά τεμάχια Νάρθηκας, Εξωνάρθηκας Συμπαγείς πλίνθοι Ενισχυτικές ζώνες από λαξευτούς ευμεγέθεις λίθους (βάση και γένεση των τόξων) Διαστάσεις πλίνθου Μήκος: 30-36 cm Πάχος: 3,5-4 cm Κονίαμα αρμών : 6-7 cm The Hagia Sophia Bricks Lightweight - High Strength - Microporous bricks <ul><li>Hagia Sophia Masonry Technology </li></ul><ul><li>Dome construction: </li></ul><ul><li>compact bricks bound with strong, hydraulic, crushed brick mortars </li></ul><ul><li>Narthex and Outer-Narthex </li></ul><ul><li>Compact bricks bound with strong hydraulic crushed brick mortars </li></ul><ul><li>Reinforcing zones of large sculptured stones at the arches base support and curvature </li></ul><ul><li>Brick dimensions: </li></ul><ul><li>Length 30 - 36cm </li></ul><ul><li>Height 3.5 - 4.0cm </li></ul><ul><li>Joint mortar : Height 6 - 7cm </li></ul>The bricks are similar to those used in the Great Basilica of Rhodes. However, the Hagia Sophia bricks are lighter (45% porosity) than the other bricks (35% porosity). The Hagia Sophia bricks are made of a noncalcareous, fine paste with quartz temper, fired at low temperature (750°C). Exceptional characteristics are their homogeneity and small pore-size distribution (0.3 – 0.8 μ m), as well as the unexpectedly high (up to 1.3 MPa) tensile strength of the dome bricks as opposed to their high porosity. Τ he very narrow pores, of an almost standard diameter, probably are the result of a fine sieving of the clay mix or pressing of the brick molds or of levigation or grinding, as well as of accurate-stable firing temperature and controlled furnace atmosphere. Hagia Sophia, Upper South Gallery, Arch area where bricks, mortars and stone are visible after removal of the mosaic layer during conservation interventions Photo courtesy A. Moropoulou
  31. 31. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Forming of ceramics Forming of the raw material to its final shape is accomplished either manually (e.g. during the manufacture of classic pottery) or at an industrial or semi-industrial scale with appropriate devices or molds . In both cases, pressure is applied to form the final shape. The pressure depends on the forming technique: Wet method : Clay contains enough water so that it has adequate plasticity Dry method : Clay is almost dry and requires high pressure in order to form the final shape Historic ceramics manufacturing process <ul><li>Selection of clay based on the desired use of the ceramic </li></ul><ul><li>Cleaning and precipitation process depending on the required quality of the final product </li></ul><ul><li>Mixing of clay with sand or ground limestone depending on the desired properties of the ceramic product </li></ul><ul><li>Forming of the ceramic article with hands, ceramic wheel of molds -> green ceramic </li></ul><ul><li>Drying of the green ceramic under controlled conditions </li></ul><ul><li>Sintering in a kiln with the appropriate atmosphere depending on the desired properties of the final ceramic product </li></ul>Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  32. 32. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Drying of ceramics Drying aims to remove the water that was necessary for forming the “green ceramic”. It is a process that needs to be careful designed so that cracks and shape deformations are avoided. Diffusion of water from the interior of the ceramic body to its external surface, where it can evaporate, needs to be performed gradually. Two methods are usually employed: Natural drying : The green ceramics are placed under well ventilated sheltered areas, and when they have dried adequately, they are placed on open air, under direct sunlight to dry completely Technical drying : The green ceramics are placed in specially designed chambers where either hot air from the kiln is fed, or their floors and walls are heated by the kiln exhaust air. Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  33. 33. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Sintering of ceramics Sintering aims to stabilize the shape of the ceramic and allow it to obtain its final physical and mechanical properties, such as mechanical strength, impermeability, surfacial hardness etc. Sintering removes the pores from the ceramic matrix, in effect shrinking the ceramic article, while in parallel, “gluing” the grains together, creating a strong body. It is a process that has to be carefully designed, and it still has the form of an “art”. The design of the kiln, the temperature it can reach, the placement of the ceramic articles inside the kiln, the atmosphere of the kiln (oxidizing or reducing), the heating rate and heating pattern (temperature plateaus), the cooling rate and cooling pattern, all play an important role in obtaining the desired properties. Schematic of the sintering process : ( Top left - Green material ) the porosity of the green body is between 40-60%. ( Top right - Initial stage ) as the temperature increases to the sintering temperature, “necks” between the grains are formed and grow. ( Bottom left - Intermediate stage ) material diffuses into the pores, the pores are changing from irregular to a cylindrical shape, and grain growth takes place ( Bottom right - Final stage ) the cylindrical pores become spherical and closed. Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  34. 34. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Characterization of ceramics Scanning Electron Microscopy (SEM): Analysis of the ceramic’s microstructure and the vitrification state X-Ray Diffraction (XRD) Chemical analysis and phase identiication Mercury porosimetry Assessment of the degree of sintering, and analysis of the ceramic’s microstructure Thermal Analysis Differential Thermal (DTA) and Thermogravimetric (DTG) Analyses essentially provide a thermal “fingerprint” of the ceramic and besides revealing its composition they also allow the deduction of its provenance and manufacturing process Mechanical tests The mechanical properties of interest are compression strength and the modulus of elasticity Schematic presentation of a DTA curve for clay Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Moropoulou, A., Bakolas, A., Bisbikou, K., &quot;Thermal analysis as a method of characterizing ancient ceramic technologies”, Thermochimica Acta , 2570 (1995) pp. 743-753
  35. 35. Educational Linkage Approach In Cultural Heritage 2. 5 .2. Historic building materials - Ceramics Thermal Analysis as a method of characterization of historic ceramics Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Moropoulou, A., Bakolas, A., Bisbikou, K., &quot;Thermal analysis as a method of characterizing ancient ceramic technologies”, Thermochimica Acta , 2570 (1995) pp. 743-753 Ca-rich ceramic Ca-poor ceramic The alternate presence of augite , anorthite (XRD results) gives indications as to the role of CaO transformations in the ceramic matrix. From the two qualities distinguished according to texture and colour, generally, red bricks show extensive vitrification with iron oxide phases dispersed almost homogeneously in the vitreous matrix and buff bricks show fragmented vitrification, where lower concentrations of iron oxides are observed, allocated to large haematite crystals surrounded by lemonite. The behaviour of red bricks is governed by the CaO% transformed into the anorthite phase , releasing iron oxides by firing in alternate oxidizing/reducing atmosphere. Buff bricks in contrast, present a higher CaO% transformed into an extended calcium aluminosilicate microcrystalline development , which explains the inhibition and finally the more fragmented vitrification observed, along with the colour difference, due to the trapping of iron in the augite lattice.
  36. 36. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Mortars - Components <ul><li>Binding material </li></ul><ul><ul><li>Lime putty: It cures and hardens when it comes in contact with air (gypsum, air-cured lime) </li></ul></ul><ul><ul><li>Hydraulic lime: It cures and hardens in the presence of water, with or without the presence of air and remains hard even in water (hydraulic lime, cement) </li></ul></ul><ul><li>Aggregates: materials in grainy form, that are used as fillers in mortars </li></ul><ul><ul><li>Natural aggregates: stones, pebbles, gravel </li></ul></ul><ul><ul><li>Industrial aggregates: expanded argil, perlite and vermiculite </li></ul></ul><ul><li>Additives: t hey are used to improve certain properties of the mortars </li></ul><ul><ul><li>Inorganic - pozzolanas (natural, artificial pozzolanas, crushed bricks et als.) </li></ul></ul><ul><ul><li>Organic </li></ul></ul><ul><li>Water </li></ul>Mortars – Classification based on their use Joint mortars: Binding material of structural elements Substrate mortars: Substrate in the form of layers used in floors, mosaics, frescoes Plasters: A form of surface layering. It is a protective layer for corrosive factors (rain, humidity), or for decorative purpose Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  37. 37. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Characterization of mortars X-Ray Diffraction (XRD) Mineral phases dispersion and mineral analysis of crystal phases Petrographical Analyses / optical / fibre optics / electron microscopy Structure textural and microstructural characteristics Gradation Binder to aggregates ratio Thermal Analysis Phases and composition (Classification to basic categories) Mechanical tests Mechanical properties mainly compression strength and modulus of elasticity Mercury porosimetry, Digital image procesing on microscopical investigation et als Microstructural analysis Water capillary rise tests, water vapor permeability % absorbed water, capillary rise coefficient NDT (DIP, IR Thermography, Ultrasonics, colorimetry, etc.) in situ Classification of mortars in monuments of the Mediterranean Basin <ul><li>Typical lime mortars </li></ul><ul><li>Hydraulic lime mortars </li></ul><ul><li>Lime-pozzolana mortars </li></ul><ul><li>Crushed brick-lime mortars </li></ul><ul><li>Rubble masonry mortars </li></ul>Acceptability limits for the production of restoration mortars Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials
  38. 38. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Characterization of mortars Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Correlation between the tensile strength (Fmt.k) and hydraulicity of mortars (inverse CO 2 / structurally bound water) Moropoulou, A., Bakolas, A., Michailidis, P., Chronopoulos, M., Spanos, Ch., “Traditional technologies in Crete providing mortars with effective mechanical properties”, Structural Studies of Historical Buildings IV, ed. C.A. Brebbia, and B. Leftheris, Computational Mechanics Publications, Southampton Boston, Vol. 1 (1995) pp. 151-161
  39. 39. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Typical lime mortars GRADATION THERMAL ANALYSIS Typical Lime Mortar from the Medieval City of Rhodes Fibre Optics Microscopy image from a Typical Lime Mortar MICROSTRUCTURE Total Porosity: 30 – 35% Average Pore Radius: 0.8 – 3.3 μm Density: 1.5 – 1.8 g/cm 3 Specific Surface Area: 1.3 – 3.3 m 2 /g Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Binder/aggregates ratio: 1:2 – 1:3 Μoropoulou, A., Bakolas, A., Bisbikou, K., “ Investigation of the technology of historic mortars ” , J. Cultural Heritage, 1 (2000) pp. 45-58
  40. 40. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Hydraulic lime mortars MICROSTRUCTURE Total Porosity: 18 – 40% Average Pore Radius: 0.1 – 3.5 μm Density: 1.7 – 2.1 g/cm 3 Specific Surface Area: 2.5 – 13.5 m 2 /g Arkadi Monastery Fibre Optics Microscopy image from a Hydraulic Lime Mortar GRADATION THERMAL ANALYSIS Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Binder/aggregates ratio: 1:2 – 1:3 Moropoulou, A., Bakolas, A., Michailidis, P., Chronopoulos, M., Spanos, Ch., “ Traditional technologies in Crete providing mortars with effective mechanical properties ” , Structural Studies of Historical Buildings IV, ed. C.A. Brebbia, and B. Leftheris, Computational Mechanics Publications, Southampton Boston, Vol. 1 (1995) pp. 151-161
  41. 41. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Prof. Antonia Moropoulou – Topic 2: Knowing the built heritage Lime pozzolana mortars MICROSTRUCTURE Total Porosity: 30 – 42% Average Pore Radius: 0.1 – 1.5 μm Density: 1.6 – 1.9 g/cm 3 Specific Surface Area: 3 – 14 m 2 /g Image from Cisterns /Lavrio Fibre Optics Microscopy image from a Lime pozzolana Mortar GRADATION THERMAL ANALYSIS Binder/aggregates ratio: 1:2 – 1:4 Μoropoulou, A., Bakolas, A., Bisbikou, K., “ Investigation of the technology of historic mortars ” , J. Cultural Heritage, 1 (2000) pp. 45-58
  42. 42. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Crushed brick lime mortars MICROSTRUCTURE Total Porosity: 32 – 43% Average Pore Radius: 0.1 – 0.8 μm Density: 1.5 – 1.9 g/cm 3 Specific Surface Area: 3.5 – 15 m 2 /g Crushed Brick Lime Mortar / Hagia Sophia masonry Fibre Optics Microscopy image from the same mortar GRADATION THERMAL ANALYSIS Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Binder/aggregates ratio: 1:2 – 1:4 Moropoulou, A., Cakmak, A.S., Biscontin, G., Bakolas, A., Zendri, E., “ Advanced Byzantine cement based composites resisting earthquake stresses: The crushed brick-lime mortars of Justinian ’ s Hagia Sophia ” , Construction and Building Materials, 16 [18] (2002) pp. 543-552
  43. 43. Educational Linkage Approach In Cultural Heritage 2. 5 .3. Historic building materials - Mortars Prof. Antonia Moropoulou – Topic 2 .5 : Historic building materials Hot lime technology mortars Rubble masonry mortars Photo from Simonos Petra Arsenal in Mount Athos Fibre Optic Microscopy image In situ slaking of lime / day admixture Photo from the Medieval City of Rhodes Fibre Optic Microscopy image shows adhesion between the stone and the mortar Binder/aggregates ratio: 1:2 – 1:4 Moropoulou et als, “Hot lime technology imparting high strength to historic mortars”, Construction and Building Materials, 10, No 2 (1996) pp. 151-159 Moropoulou, A. et als. “ Technology and behavior of rubble masonry mortars ” , Constr. & Build. Mat. , 11, No 2 (1997) pp. 119-129 Binder/aggregates ratio: 1:2 – 1:4

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