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Study of Materials Behavior for Use in Cultural Heritage
Laboratory of Materials Science and Engineering - School of Chemical Engineering - National Technical
University of Athens, Greece Scientific Responsible Prof. Antonia Moropoulou
21-10-2014
NTUA-LMSE LAB PROF. A. MOROPOULOU
Materials and Cultural Heritage
Against which problems do we need
to safeguard built cultural heritage?
Problems due to the decay of materials and
structures, imposed by environmental factors or
by past interventions
Built Cultural Heritage faces characteristic damage factors:
the atmosphere (marine, pollution, temperature cycles, etc) water (salt-decay, rising damp, etc) seismic actions usage-related damage (tourism)
NTUA-LMSE LAB PROF. A. MOROPOULOU
Materials and Cultural Heritage
Historically, construction technology has incorporated significant empirical knowledge about the behaviour of
structures under the prevailing decay factors
It is therefore important to reveal this empirical knowledge that has already been integrated into these structures, during their construction and during past interventions, and utilize it
when designing and implementing interventions for the safeguard of CH
NTUA-LMSE LAB PROF. A. MOROPOULOU
The significant role of Materials Science in Built Cultural Heritage Protection
Diagnostic Study Identify the decay mechanisms and assess the decay state of the building
Monitoring, Control, Maintenance – Introduction of Quality Control Monitoring of the decay factors and the building’s deterioration
Design of Appropriate Conservation Materials and Interventions Intervention study that addresses the decay with an effective & compatible solution
Intervention Works Application of designed intervention following strict specifications and procedures
Quality Control of Intervention Works Assessment of Intervention Effectiveness through characteristic indices
Scientific Support to Decision Making regarding Intervention Necessity
Integrated Documentation Knowing the building
NTUA-LMSE LAB PROF. A. MOROPOULOU
How do we Understand the Building
Intrinsic Data Extrinsic Data
UNDERSTAND THE BUILDING
Church of the Holy Sepulchre, Jerusalem, Prof. A. Moropoulou
THE DECAY PHENOMENA DEVELOP AT THE
INTEFACES OF
MATERIALS / ENVIRONMENT
OR MATERIALS / MATERIALS
AND ARE A FUNCTION OF INTRINSIC
AND EXTRISIC FACTORS
NTUA-LMSE LAB PROF. A. MOROPOULOU
Documentation – Intrinsic Data
General information for the building
(general description, type, location, ownership & legal status, etc)
Historical documentation
Surveying documentation
Architectural documentation
Archaeological survey documentation
Structural documentation
Materials characterization and mapping
(type, properties, production technology, compatibility with other materials)
- Structural materials
- Nonstructural / Decorative / Surfacial materials
Documentation of past conservation and/or protection interventions
Value of the building
- Historical value
- Aesthetic value
NTUA-LMSE LAB PROF. A. MOROPOULOU
Documentation – Extrinsic Data
Environmental factors
- General climate characteristics, microclimate
Atmosphere
- Polluted (Concentration and distribution of air pollutants)
- Marine (Effect of salt spray)
Water
- Aerosol, precipitation, rising damp, condensation, salt crystallization
Biologic factors (fauna and flora)
Usage of building
- Building environment / urban and land use & planning, interior environment, visitors patterns
Mechanical loadings
- Temperature fluctuations, effect of differential thermal expansions of materials, salt crystallization, frost damage, earthquake vibrations, abrasion
NTUA-LMSE LAB PROF. A. MOROPOULOU
Materials Decay Diagnosis Methodology
Documentation
In situ macroscopic observations for materials’
decay state and type, and structures’ pathology
Monitoring of the
acting environmental factors
In situ NDT- Decay mapping
(environmental impact assessment)
Building materials’ characterization
and study of their provenance
In lab study of decay products and
Mechanisms (microscopic scale)
Correlation of intrinsic and extrinsic
factors on the monument scale
Working hypothesis on the prevalent acting
environmental factors and decay mechanisms
DIAGNOSIS Parametric analysis - Simulation of the
phenomena under accelerated ageing
(comparison of various scenarios)
Assessment Methodology NTUA-LMSE LAB PROF. A. MOROPOULOU
How Building Documentation is realized
Surveying Documentation
In order to understand what is the current state (decay) of the building, so that we intervene appropriately, surveying, structural and materials documentations need to
be integrated with the study of alterations i.e. the diagnostic study
Architectural Documentation
Structural & Materials Documentation
Alterations / Interventions
Complete “picture” of the current state of the building
Integrated Diagnostic Study
NTUA-LMSE LAB PROF. A. MOROPOULOU
Monitoring of the acting environmental factors
In situ macroscopic observations for material’s decay state and type and structure’s pathology Materials decay state Type of decay phenomena Record any interventions
In situ NDT – Decay mapping (environmental impact assessment) Materials mapping Weathering mapping Assessment of environmental effects
Microclimate
Temperature, humidity, precipitation, speed, direction and frequency of winds, etc
Pollutants Aerosols, drain waste & leakages, solid waste
Soil and Damp Chemical analysis of the soil and monitoring of the rising damp
Salts In liquid or solid state
NTUA-LMSE LAB PROF. A. MOROPOULOU
Non Destructive Techniques for Decay Diagnosis
Destructive sampling is prohibited in the conservation of historic monuments
They offer certain unique capabilities in a variety of applications
Non-Destructive Techniques (NDT) are used in Cultural Heritage protection because:
Ultrasonics Infrared Thermography Fibre Optics Microscopy Digital Image Processing
Ground Penetrating Radar Colorimetry
Applications
Materials quality control, as well as for technology
assessment regarding the production of advanced
materials
Environmental impact assessment - materials and
weathering mapping
Evaluation of conservation materials compatibility
and conservation interventions effectiveness on
the scale of architectural surfaces and historic
masonries
Strategic planning for the conservation
interventions.
Environmental management for the protection of
Cultural Heritage
NTUA-LMSE LAB PROF. A. MOROPOULOU
NDTs - Ultrasounds
Basic Principles Measures the velocity of ultrasounds traveling through a media, which depends on the media’s density and the presence of voids and cracks. Applications Estimation of the depth of the decay patterns (crusts, cracks etc), evaluation of the effectiveness and the depth of penetration of restoration interventions.
NTUA uses a Portable Ultrasonic Non-Destructive Indicating Tester (PUNDIT) with
transducers of various frequencies
Depth of Crust
A Β C
T: Transmitter R1 R2 R3 R4 : Receiver
A Β C
T: Transmitter R1 R2 R3 R4 : Receiver
2/1
2 DS
DSo
VV
VVl
where Vs, VD, are the ultrasonic velocities in the healthy and damaged part of the stone, respectively and lo the distance between the transducers where a change in slope of
the distance-time curve is observed
Evaluation of Pilot Consolidation Interventions: Penetration depth of consolidation material
0 20 40 60 80 100 120
Distance (X, mm)mm)
0
20
40
60
80
100
120
140
160
Rodos Ag. Aikaterini - P-wave Site PH
T
D1=15.3mm
D2=21.1mm
Moropoulou, A., Tsiourva, Th., Theoulakis, P., Christaras, B., Koui., M., “Non destructive evalution of pilot scale treatments for porous stone consolidation in the Medieval City of Rhodes”, PACT, J. European Study Group on Physical, Chemical, Biological and Mathematical Techniques Applied to Archaeology, 56 (1998) pp. 259-278
G. Batis, A. Moropoulou “Non-destructive testing of materials – Ultrasonics” in Laboratory notes of the Course 5202 “Building Materials” School of Chemical Engineering, National Technical University of Athens, pp. 69-77 (2011)
NTUA-LMSE LAB PROF. A. MOROPOULOU
NDTs – InfraRed Thermography
Basic Principles Measures the thermal radiation (infra-red range in the electromagnetic spectrum) emitted by materials and renders an image of the surface area in pseudo-colors which are related to a temperature scale Applications Identification of decay patterns on monuments, assessment of physicochemical compatibility of materials & structures, detection of defects in materials or structures, study of water transport mechanisms NTUA uses FLIR System B200 IR camera
[7.5-13 μm / Thermal sensitivity 70mK]
Evaluation of restoration materials: Monument scale
Venetian Fortifications of Heraklion
Pentelic Marble, Athens
Academy
Before cleaning After cleaning
Cleaning Method: wet micro blasting method, particles of spherical calcium carbonate, d< 80μm, P<1 atm, suspension’s proportion 2:1
Evaluation of pilot cleaning interventions: Monument scale
The incompatibility of replacement stones is indicated by the difference in temperature compared with the historic materials
Avdelidis, N.P., Moropoulou, A., “Applications of infrared thermography for the investigation of historic structures: a review study”, Journal of Cultural Heritage, 5 [1] (2004) pp. 119-127
Moropoulou, A., Avdelidis, N.P., Delegou, E.T., Koui, M., «Infrared thermography in the evaluation of cleaning interventions on architectural surfaces», in Proc. INFRAMATION Int. Conf. on infrared thermography, Orlando (2001) pp. 171-175
NTUA-LMSE LAB PROF. A. MOROPOULOU
NDTs – Fibre Optics Microscope
Basic Principles Captures images in the visible spectrum. Image is transmitted via optical fibres and then transformed into electric signals which are stored in a video unit or digitized and stored on a computer Applications Identifies differences in the texture and composition of surfaces, materials classification, microstudy of the decay phenomena, evaluation of restoration interventions
ELAICH – Athens Experimental Course: In situ use of fibre optics microscopy to
identify the decay patterns on marble surfaces at the archaeological site of Eleusis
Investigation of materials’ surface morphology Evaluation of consolidation interventions
6th Century Mosaic (x50), Hagia Sophia, Dome
Weathered Mortar Surface (x50), Hagia Sophia, N/W Outer
Narthex
10th Century Mosaic (x50), Hagia Sophia, Dome
Inner Part of Compact Mortar Surface (x25), Hagia Sophia, N/W Outer
Narthex
Clay Plaster (x25), Stadiou Historic Building in Athens
Interface of Cement Plasters (x25), Stadiou Historic Building in Athens
Untreated Surface, Rhodes Porous Stone
(x50),
Surface treated with PH (pre-ydrolysed ethyl silicate with amorphous silica)
(x50)
Surface treated with PL (aqueous colloidal
dispersion of silica particles), (x50)
After consolidation treatments, information regarding microstructural modifications of porous materials, as well as the
deposition mechanism of the applied materials, can be obtained by using fibre optics microscopy
Photos 1, 2, 4, 5: Moropoulou et als (2002b), Photos 3, 6: Moropoulou et als (2005), Photos 7-9: Moropoulou et als (2000a, 2000b)
1 2 3
4 5 6
NTUA-LMSE LAB PROF. A. MOROPOULOU
NDTs – Digital Image Processing Basic Principles Depending on the material type, the surface texture and morphology, and the decay state, a variation of the reflectance and absorption of electromagnetic radiation is observed, which can be identified. Applications Images from FOM, IRT, Optical and Scanning Electron Microscopy are digitally processed identifying differences in texture and decay state of surfaces, lithotypes, and allowing material and decay mapping
Decay Mapping, National Library of Athens
Basic Principle Microstructural analysis – Image Pro X
Change of the energy content of the gray levels. The position on the x-axis is determined by the color of the material, the dispersion of the values can be correlated to the characteristics of the material and its decay state. The degree of weathering of the material is related to the width (x-axis) of the gray levels; the width increases with increasing decay state
Kapsalas et als (2007)
1. Optical microscopy image 2. Conversion to grayscale – Gray level histogram
3. Process – Segmentation / Threshold 4. Microstructural analysis A. Moropoulou, A. Konstanti “Laboratory notes on digital image processing”, Interdepartmental
Postgraduate Course “Protection of monuments, sites and complexes”, Nat. Techn. Univ of Athens
Moropoulou, A., Koui, M., Theoulakis, P., Kourteli, Ch., Zezza, F., “Digital Image Processing for the Environmental Impact Assessment on Architectural Surfaces”, J. Environmental Chemistry and Technology, 1 (1995) pp. 23-32
NTUA-LMSE LAB PROF. A. MOROPOULOU
NDTs – Ground Penetrating Radar Basic Principles A short electromagnetic pulse (10MHz – 10GHz) is produced and propagated into the structure, part of the pulse energy is reflected (due to the presence of internal interfaces between materials of different dielectric constant), rendering a 2-D or 3-D image of the sub-surface Applications Reveal internal structure of masonries, location of cavities, identification of detachments and internal cracks, assessment of decay depth NTUA uses the MALÅ ProEx system with
1.6GHz and 2.3GHz antennas and RadExplorer v.1.41 software
Decay state of the structure - Church of the Holy Sepulchre Evaluation of the decay state of mosaics – Hagia Sophia
(Left) Presence of two cracks (T1 & T2) that penetrate the external layer of the Katholikon Dome Base. (Right) Presence of three double reinforcing bars A1, A2, A3 and a reinforcing matrix 5x5cm B1 (Moropoulou et als Report to the Patriarchate of Jerusalem on NDT Assessment of the Church of the Holy Sepulchre, NTUA, 2011)
Katholikon NW Dome base (exterior)
Katholikon north view of the north masonry (interior
of the church)
Areas around the revealed mosaic where the presence of void spaces below the plastered mosaic layer has been identified by ground penetrating radar
The space indicated with dashed line is possibly filled with mortar and bricks. Care should be taken at this junction area regarding the cohesion of the preserved mosaic with its support mortar and the structure (Moropoulou et als, 2012)
NTUA-LMSE LAB PROF. A. MOROPOULOU
Validation of NDTs by Laboratory Techniques
Macroscopic investigation:
Classification in order of increasing
degree of alveolar decay
(V = max)
Microstructural investigation
(Mercury Intrusion Porosimetry):
Pore volume distribution for each
degree of alveolar decay
DIP
Moropoulou, A., Koui, M., Kourteli, Ch., Achilleopoulos, N., Zezza, F., “Digital image processing
and integraded computerised analysis for weathering on planning conservation interventions on
historic structures and architectural complexes”, in Proc. EURISCON Conference on European
Robotics, Intelligent Systems and Control, Publ. International Association for Mathematics and
Computers in Simulation (1999)
Theoulakis, P., Moropoulou, A., “Microstructural and mechanical parameters determining the susceptibility of porous building stones to salt decay”,
Construction and Building Materials, 11, No. 1 (1997) pp. 65-71
NTUA-LMSE LAB PROF. A. MOROPOULOU
Validation of NDTs by Laboratory Techniques
Hard Carbonate Crust: Medieval City of Rhodes
(Combined assessment with the use
of NDT and validation with SEM)
Fibre Optics Microscopy
Digital Image Processing
Scanning Electron Microscopy
Alveolar Weathering Medieval City of Rhodes
(Combined assessment
with the use of NDT and
validation with SEM)
Fibre Optics Microscopy
Digital Image Processing
Scanning Electron
Microscopy
Moropoulou, A., Koui, M., Tsiourva, Th.,
Kourteli, Ch., Papasotiriou, D., “Macro- and
micro non destructive tests for
environmental impact assessment on
architectural surfaces”, Materials Issues in
Art and Archaeology V, Vol. 462, ed. P.B.
Vandiver, J.R. Druzik, J.F. Merkel, J.
Stewart, Publ. Materials Research Society,
Pittsburgh (1997) pp. 343-349
NTUA-LMSE LAB PROF. A. MOROPOULOU
Building Material’s Characterization
Mineralogical & Petrographic analyses
Chemical analysis (chemical structure)
Physical analysis (e.g. grain size distribution)
Physicochemical analysis (e.g. density, porosity, permeability)
Mechanical analysis (e.g. compression strength, tensile strength, modulus of elasticity, fracture toughness)
NTUA-LMSE LAB PROF. A. MOROPOULOU
Parametric analysis - Simulation of the phenomena under accelerated ageing
The simulation of the decay phenomena in a laboratory allows for detailed monitoring – under controlled conditions – of the time evolution of decay and for collection of data quantifying its mechanism. Furthermore, it is a useful assessment method for the effectiveness of various protection interventions
Salt spray chamber
Durability of surface protection interventions against salt spray
Environmental Test Chamber Wetting – Drying cycles
Durability of materials against decay factors
(Temperature, rel. humidity, pollutant gases, UV radiation)
Durability of materials against decay from salt crystallization
Weight variation values of untreated and treated porous stone as a function of days of exposure
Moropoulou, A., Kouloumbi, N., Haralampopoulos, G., Konstanti, A., Michailidis,
P., “Criteria and methodology for the evaluation of conservation interventions on treated porous stone susceptible to salt decay”, Progress in Organic Coatings, 48
[2-4] (2003) pp. 259-270
Accelerated aging tests (SO2 . 95% Relative humidity, T=25oC) for various mortar types
Dry weight conc. of bisulfite or sulfuric salts
Relevant data C. Sabbioni, “Assessment of damage caused by air pollution” ITECOM Advanced Study Course and Materials for the Conservation of Monuments, 8-20/12 Athens, (2003)
Salt crystallization test results Cycle description Commision 25-PEM Test No V.1b, sodium suplphate immersion - drying cycles, Materiaux et Constructions, 13 (75) a. 2 hours immersion in 15% Na2SO4solution b. 20 hours drying at 75oC c. 2 hours at room temperature d. 20 hours curing in an atmosphere with a high relative humidity e. 2 hours at room temperature
C Consolidation treatment: Calcium hydroxide suspension 10% (w/v)
F Water repellency treatment: Fomblin CO Slate fluoroelastomer (100g/m2)
CF Combination of C & F
Moropoulou, A., Theoulakis, P., Dogas, Th., “The behaviour of fluoropolymers and silicon resins as water repellents under salt decay conditions in combination with consolidation treatments on highly porous stone”, Science and Technology for Cultural Heritage, 3 (1994) pp. 113-122
NTUA-LMSE LAB PROF. A. MOROPOULOU
Cultural Heritage Protection - Decision Making
SCIENTIFIC SUPPORT TO DECISION MAKING
Diffusion of results to end-users
RESEARCH - INNOVATION
Historic documentation
Characterization of historic materials and structures
DECAY DIAGNOSIS
Evaluation of previous conservation interventions
Assessment of environmental
impacts
Quality control of restoration
materials
Pilot application of conservation interventions
ASSESSMENT
Evaluation of pilot applications in lab scale
and in-situ
NTUA-LMSE LAB PROF. A. MOROPOULOU
Conservation Materials and Interventions
Preconsolidation (only on cases of extreme decay)
Cleaning (mechanical, physical or chemical removal of surface depositions)
Consolidation (rehabilitation of the cohesion of the decayed material)
Surface protection (protection of building materials from environmental factors)
Restoration (compatible materials & interventions)
Treatment against rising damp (allowing masonries to “breath”)
Integration Restoration of the unit (structural interventions) Reconstruction of the building (architectural interventions)
NTUA-LMSE LAB PROF. A. MOROPOULOU
Materials Use in Cultural Heritage
They take advantage of recent accomplishments in nanotechnology
and the ability to design and manufacture materials at the
nanoscale.
Past experience (successes and failures)
Better understanding of problems
Recent technological advances
Improve existing materials and
techniques
“Smart” materials
More intense environmental factors
Need for improvement
Sustainability Public awareness
They reached their limits in terms of properties, applicability, compatibility,
and durability
NTUA-LMSE LAB PROF. A. MOROPOULOU
Materials in Cultural Heritage Protection
The capacity to be able to design rather than use whatever is available is of utmost importance for compatible and effective conservation interventions
“Smart” materials offer many advantages over established conservation materials and support the development of innovative protection techniques
Innovation is driven by necessity to solve imminent problems in Cultural Heritage protection
NTUA-LMSE LAB PROF. A. MOROPOULOU