Study of Materials Behavior for Use in Cultural Heritage ITN-DCH Project 1st... · Study of...

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)


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


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


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


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


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


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


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


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


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)


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


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


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


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)


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


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


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)


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


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


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)


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


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


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