prof. lucia toniolo laboratory «materials and methods...

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Conservation and monitoring of historical architecture: new materials and technologies

Prof. Lucia TonioloLaboratory «Materials and Methods for Cultural Heritage»Department of Chemistry, Materials and Chemical Engineering“Giulio Natta” [email protected]

Lucia Toniolo – Politecnico di Milano

Cultural Heritage threatening: a complex problem

Information on both the air quality and microclimate are needed to effectively

evaluate cultural heritage conservation methods !

The issue of conservation of the architectural heritage is strongly related to air pollution.

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Lucia Toniolo – Politecnico di Milano3

Heritage Conservation? What does it mean?In Europe

60 YEARS


Angkor Wat, CambodiaAngkor Wat, Cambodia1995 2006

Heritage Conservation? What does it mean?In Asia

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(da E.M. Winkler “Stone in Architeture” 1994)

Visual rate of stone decay


6Degradation of outdoor exposed stone materials

The process of degradation is the adaptation of stone materials to the prevailing environmental condition

The process of degradation occurs at the very surface of the building, that is the interface material/environment

During XXth cent. the kinetic of the process has been dramatically increased thanks to atmospheric pollution

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7/65

Architectural Heritage durability

Architectural Heritage durability

materialmaterial environmentenvironment

ChemicalpropertiesChemicalproperties

Mechanical properitiesMechanical properities

Physical propertiesPhysical

propertiesClimateClimate

Air quality & pollution

Air quality & pollution

Micro-climateMicro-climate

Interaction Material / Environment

Petrographicalproperties

Petrographicalproperties


CeramicsNatural Stones, RocksLime, Gypsum, CementMortars & ConcreteBricks & TerracottaMasonries

CeramicsNatural Stones, RocksLime, Gypsum, CementMortars & ConcreteBricks & TerracottaMasonries

MetalsIron alloys, steelCopper alloys, bronzesAluminumTitanium

MetalsIron alloys, steelCopper alloys, bronzesAluminumTitanium

Synthetic PolymersPolymeric materials, PlasticsVernishes & PaintingsFibersComposites

Synthetic PolymersPolymeric materials, PlasticsVernishes & PaintingsFibersComposites

Organic MaterialsWood and TimberLeather

Organic MaterialsWood and TimberLeather

Architectural Heritage:Not only ceramics, not only concrete!

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10,500 m2 of marble12 spires500 sculptures25 large low-relieves

1961

2000

High value Architectural Heritage 1. Milan, the Cathedral


10The scaffold

The scaffold has been built at the end of 2002 The conservation work has been finished at the end of 2009

2003 2005

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11High historical-artistic value Cultural Heritage 2. Certosa di Pavia


12High historical-artistic value Cultural Heritage 3. La Collegiata di Castiglione Olona (Varese)

1425

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13Fresco painting by Masolino da Panicale

1434


Fresco painting by Masolino da Panicale

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High historical-artistic value Cultural Heritage 4. Torre Velasca, Milan 1958 Architect Studio BBPR


16How to face this very difficult situations?

4 dramatically important keywords

1. Multi-disciplinarity2. Knowledge3. Compatibility4. Reversibility/Retraetability

Project guidelines

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E. Doehne, C.A. PriceStone Conservation: An Overview of Current Research (Readings in Conservation)Getty Conservation Institute, Los Angeles 2010

S. Sigesmund, R. SnethlageStone in Architecture: Properties, DurabilitySpringer-Verlag 2011

Three Reference Books

S. Macdonald and G. OstergrenConserving Twentieth-Century Built Heritage:A BibliographyGetty Conservation Institute, Los Angeles 2013


Scientific publication on “conservation treatments” (in english) and case studies presenting the evaluation of treatment performances are only a few !!

Multidisciplinarity for the Conservation project

Book Article, Journal Article, Patent - "Conservation Treatment" as subject - in Architecture and Archaeological conservation - in the period 2000-2014From AATA online, Getty Conservation Institute, http://aata.getty.edu/Search

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Restoration and maintenancefor natural stone1.Cleaning2.Surface Consolidation3.Adhesion, Sealing4.Surface Protection

Knowledge & Compatibility

... what kind of treatment?

“There is hardly a polymer which has not been suggested and used for a conservation application”

C.V. Horie 1990

Phases of the conservation work


Polymeric materials

Polymer Class Years Types Apllication

Vinyl resins1950 LDPE, PE, PP Stone, Mural Painting,

Painting, Papersynthetic gums

Substituted Vinyl resins

1950-60 PVC, PVAC, PS, PEG

Stone, Paper, Textile, Painting, Wood

Acrylic Resins 1930 Lucite 44/45 vernishes1970 Paraloid, Elvacite,

PlexigumStone, Mural piantings, Paintings, Wood

PMMA, PBMAPolyurethanes 1970 Wood, Stone

Epoxy Resins1950 Stone, Mural paintings,

Metals

Silicon Resin

1975 DRI FILM 104, Rhodorsil, Silirain,TEOS, MTMOS,

Stone, Bricks, Plaster, Paper, Antigraffiti

Perfluoro polyethers

1980 Fomblyn, Akeogard Stone, Plasters, Antigraffiti

Fluorurated acrylic resins

1995 Stone

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Ideal surface consolidation treatment 21

Good adhesion to the stone substrate

Negligible color alteration

Adds no gloss or sheen

Improvement of mechanical and microstructuralproperties

Do not produce any harmful by product (salts, VOCs, organic compounds, etc.)

requirements


MATERIALS FOR SURFACE CONSOLIDATION

Inorganic compounds - Low molecular weight•Lime (Ca (OH)2) and nanolime•Barium hydroxide (Ba(OH)2)•Ammonium oxalate

Organic esters of silicic acid•Tetraethyl orthosilicate (TEOS)•Tetramethyl orthosilicate (MTMOS)

Organic synthetic polymers•Siloxanes•Acrylic polymers•Fluorinated polymers•Epoxy resins

TEOS

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Negligible color alteration

Adds no gloss or sheen

Applies as a waterborne system

Water repellent

Water vapor permeable

Stable under a variety of environmental conditions, including temperature cycling and UV exposure

Reversible or retreatable

Ideal protection/water-repellent treatment

Requirements:


Polymeric materials•Acrylic resins, partially fluorunated acrylic resins•Silicon resins, polysiloxanes•Perfluoropolyethers•Fluorinated elastomers

24MATERIALS FOR SURFACE PROTECTION

They play the role of water-repellent coating for stonesThe effectiveness depends on:

•Chemical nature•Molecular weight •Glass transition temperature•Filming properties

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Conservation project and intervention

Materialcharacterization

Environment characterization

In field diagnostic investigations

In field testing of materials and

methods

In Lab diagnostic analyses

Guidelines for conservation

Conservation project

executiveConservation and maintenance project

preliminary in field inspection 3D Survey-Mapping and sampling


Pavia – S. Michele - 1962consolidamento inorganico a basso p.m.con fluosilicati Milano – Duomo facciata – 1972Consolidamento e integrazione con materiali organici polimerici

Some experiences in surface consolidation & protection

S. Maria delle Grazie – 1985consolidamento e protezionecon materiali organici polimerici

Milano – Cortile richiniano della Ca’ Granda 1993Consolidamento con materiale organico polimerico

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The faҫade of the Milan Cathedral –Conservation work 2002-2009


Comparison between two well known marbles 28

Certosa di Pavia

Carrara marble Candoglia marble

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San Giacomo Minore, Elia Vincenzo Buzzi 1812Restored in 1972

Cathedral façade, MilanSituation of the marble sculptures in 2003


Cathedral of Milan

Surface consolidation carried out in 1972

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Polished cross-section observed by optical microscopy

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Polished cross section of a marble fragmentMicrophoto

White vernish layerTitanium dioxide

Surface consolidation layer, epoxy resin

Marble substrate


Epoxy resinWhite film, Titanium rich

Area interested by microorganismscolonization

Sample observed by Scanning Electron Microscopy32

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Surface protection carried out in 1972

Presence of yellowish surface film


in sezione trasversale

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in superficie

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Innovative strategy for surface consolidation and protectionNanotechnology in building materials

Cement and concrete: Nano-SiO2 to increase mechanical

properties and durability nano-TiO2 to reduce carbon monoxide

and NOx emissions Carbon nanotubes to enhance the

strength, to effectively hinder crack propagation

Glass: nano-TiO2 to avoid pollutant deposition nano-TiO2 super-hydrophilic

Coatings: Addition of nanoparticles

(Ag, ZnO,TiO2 ) antimicrobial and self-cleaning surfaces

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TiO2-based materials for the conservation of Architectural Heritage

• Degradation of gaseous pollutants that can be washed away by rain

• Preventive strategy towards stone degradation and biocolonization

• Reduction of time and costs for maintenance

Self-cleaningproperty

De-pollutingproperty

Biocidalproperty

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TiO2 nanoparticles used in the research

Non hydrolytic sol-gel synthesis from TiCl4 and benzyl alcohol at T= 40 °C [1,2]

Pure phase anatase

Nanoparticles size: 30±10 nm ( in water)

Benzyl groups anchored on the titania surface : photo-active not only under UV-light

but also under solar light irradiation

Highly stable dispersions of NA_TiO2 in aqueous systems, as they do not

aggregate and precipitate

Commercial P25 nanoparticles

[1] Niederberger, M. et al. Chemistry of Materials. 2002, 14 , 4364-4370[2] Colombo, A., et al. RSC Adv., 2012,2, 6628-6636

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Set-up of formulations of protective treatments for stone

and paint materials of Cultural Heritage, modified by appropriate photocatalytic TiO2 nanoparticles

1. Assessment of the efficacy and durability of the nanocomposite based on poly(2-ethyl-2-oxazoline) as consolidant and protective film for matte painting surface

2. Characterization of nano-TiO2 dispersions and study of their application on natural stones

3. Set-up and study of different hydrophilic SiO2-nano TiO2treatments for the application on natural stones

4. Set-up and study of different water repellent nanocomposites for the application on natural stones

5. Assessment of the best formulations for the protection of the façade of Monza cathedral

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Set-up of SiO2–NA_TiO2 treatments for stone conservation

Two commercial TEOS have been selected: - TEOS (A): Estel 1000, 75 wt% in white spirit D40 solvent- TEOS (B): Silres BS OH, about 100 wt%, without solvent

Application of the consolidantTetraethyl orthosilicate-TEOS as grafting agent

TiO2

NA_TiO2

SiO2

TiO2

HydrophilicSiO2-NA_TiO2 treatment

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Application of NA_TiO2 water dispersions (3%) by brush on Noto stoneand thermally aged Carrara marble:

Materials:

After the complete hydrolysis and gelation of the consolidant

(four weeks) (“wet on dry” technique)

Wet stone surface (“wet on wet” technique)

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• Every treatment shows high aesthetic compatibility with both lithotypes

Evaluation of the aesthetic compatibility: Colorimetry

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1800 1600 1400 1200 1000 800

Absorban

ce

Wavenumber (cm‐1)

1800 1600 1400 1200 1000 800

Absorban

ce

Wavenumber (cm‐1)

TEOS after 4 weeks of curingSiO2 – nano TiO2 treatment on wet surface (AWet)SiO2 – nano TiO2 treatment on dried surface (ADry)

• Formation of the silica gel• Incorporation of TiO2 into the silica network• Modification of silica network in SiO2 – NA_TiO2 treatment on driedsurface (ADry)

νa Si-O-Si

νs Si-O-Si

δ O-H

δa C-H

950

ν Si-OH

νa Si-O-Ti

910

940

Chemical interactions between TEOS and nano-TiO2: diamond cell micro-FTIR spectroscopy


Evaluation of the morphology of SiO2–NA_TiO2 treatments applied on Carrara marble section treated with Awet: SEM-EDX

Si and Ti signals in the sameregions

Ca TiSi

• Combined SiO2–NA_TiO2 layer where nanoparticles are inserted in the silica network in the “wet on wet” treatments

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• Higher values for specimens treated with “wet on wet” SiO2-NA_TiO2treatments for both lithotypes, compared to those treated only with NA_TiO2 dispersions

Evaluation of the photocatalytic activity

Noto stone

Carrara marble

+200%

+85%

+165%


Materials

1. Water dispersion of functionalizedperfluoropolyethers (10%), Fluoline PE, CTS srl

2. Water dispersion of organosiloxanes(10%), Silo 112, CTS srl

3. A solution of SiO2 functionalized by silicon alcoxides in isopropyl alcohol (20 % by weight), SIOX-5 S, Siltea srl

Development of water-repellent nanocomposites based on commercial coatings for stone protection:

Set-up of water repellent TiO2-based nanocomposites for stone conservation

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Materials

TiO2

Polymer

Preparation of the nanocomposites:

1. Blend: Fluoropolymer: 16wt% (F16mix)Polysiloxane: 16, 28 and 44 wt% (S16mix, S28mix, S44mix)Functionalised SiO2 : 16wt% (SO16mix)

2. Layered nanocomposites:

a) Application of NA_TiO2 water dispersions (3%) on wet surface

a) Application of NA_TiO2 water dispersions (3%) on dry surface


ΔΕ* <4 after the application of the treatments Lower ΔΕ* of nanocomposites compared to pristine polymers ΔΕ* <4 after the application of the treatments Lower ΔΕ* of nanocomposites compared to pristine polymers

Evaluation of the aesthetic compatibility : Colorimetry

Functionalised SiO2

PolysiloxanesFluoropolyethers

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Homogeneous distribution of treatments on the surface of both the pristine polymer (S ref) and the blends(S16mix, S28mix and S44mix)

Homogeneous distribution of treatments on the surface of both the pristine polymer (S ref) and the blends(S16mix, S28mix and S44mix)

Evaluation of the morphology of the treatments: SEM-EDX

S44mix

Ca

Si TiCa Si

S Ref

Polysiloxanes Polysiloxanes+ NA_TiO2 blend

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Pristine polymer S REF Blend nano TiO2 / polymer (16 wt% pol.) S16mix

Blend nano TiO2 / polymer (28 wt% pol.) S28mix Blend nano TiO2 / polymer (44 wt% pol) S44mix

Untreated

Evaluation of the morphology of the treatments: AFM

Polysiloxanes

50

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Increase of the roughness in nanocomposites (F16mix, S16mix, S28mix and S44mix) compared to pristine polymers (F REF and S REF)

Comparable roughness for SO16mix and SO REF

Evaluation of the morphology of the treatments: AFM

Functionalised SiO2

Polysiloxanes

Fluoropolyethers

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S44 mix

S REF SO16mixSO REF

Higher contactangles by increasing the NPs concentration

For samplestreated with functionalisedSiO2, the introduction of NPs dcreases the contact angles

Higher contactangles by increasing the NPs concentration

For samplestreated with functionalisedSiO2, the introduction of NPs dcreases the contact angles

Evaluation of the wettability properties: Static contact angle

F16mixF REFNT

Functionalised SiO2

Polysiloxanes

Fluoropolyethers

+50%+28%

-43%

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Evaluation of the photocatalytic activity

Fluoropolyethers

• Polysiloxane-based blendsshow the highestphotoactivity

• Increase of the photocathalytic activity with the increase of the NPsconcentration

• Polysiloxane-based blendsshow the highestphotoactivity

• Increase of the photocathalytic activity with the increase of the NPsconcentration

Polysiloxanes

Functionalised SiO2

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Working areas

Nor

th

Sou

th

High relief Nascita di Eva

Selected pilot areas:

• Exposition

• Architectural elements

• period of time

High relief Davide e G

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Monitoring of the Cathedral of Milan

Site 1: Road level - colour changes,

characterization of the deposit

Site 3: Main balcony. H = 19.70 m - colour

changes, characterization of the deposit

Site 5: Upper balcony. H = 32.00 m - colour


Site 4: Rear Façade (lateral nave roof).

H = 30.00 m.

Evaluation of protective treatment

Site 2: Southern Portal. H = 9.00 m - colour



Site 4: exposition conditions

South exposition

PROTECTED SPECIMENS

REFERENCESPECIMENS

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Specimen sheltered by rain: particulate matter accumulation

64

67

70

73

76

79

82

85

T‐ zero T1 ‐ 6m expo T2 ‐ 1m expo

L*

SITE 3:Variation ofLuminosity L*

Before exposition

3

4

5

6

7

8

9

T‐ zero T1 ‐ 6m expo T2 ‐ 1m expo

b*

BEFORE

EXPOSITION

Variation of b*


mm

µm

Exposed specimen: effects of rain washing out

0,0

0,2

0,4

0,6

0,8

1,0

1,2

85 86 94 95

Ra

pre expo set I ‐ 6 mesi

UNTREATEDWITH SILOXANE

COATING

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Treatment effectiveness: water repellency

BEFORE-EXPOSITION AFTER-EXPOSITION

25 misure/campione50

70

90

110

130

94 95 96

con

tact

an

gle

θ

pre expo post 6m expo


BEFORE EXPOSITION AFTER EXPOSITION

untreated

treated treated

untreated

SE

M o

bse

rvat

ion

s50

0x

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untreated untreated

treated treated

SE

M o

bse

rvat

ion

s15

00x

BEFORE EXPOSITION AFTER EXPOSITION


62What about reversibility?

Most of the treatments and chemicals used in the conservation yards aren’t reversible, that is they cannot be removed from surfaces after years.

Polymeric materials are not very durable, as it is well known for industrial products and coatings. Studies to assess durability of treatments are rare and often carried out on in laboratory not in real cases.

Conservation scientists don’t have the magic wand but are aware of limits and advantages of using different materials during intervention

Conservation projects of Heritage buildings should benefit from interdisciplinary work.

….some final remarks

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MIDAR Materials and Imaging in Arts & Architecture

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http://midar.chem.polimi.it/

PLEASE VISIT OUR WEBSITE!!


Thank you for your kind attention!

prof. lucia toniolo laboratory «materials and methods...

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