Deposition of modified nanolimes within calcareous substrates

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G. Borsoi, B. Lubelli, R. van Hees, R. Veiga, A. Santos Silva

Giovanni Borsoi: G.Borsoi@tudelft.nl

Deposition of modified nanolimes

within calcareous substrates

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Nanolime

Use: (Pre)consolidation of historical porous materials

Recover the lost cohesion

Spraying Brushing

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Calosil, IBZ, Germany Nanorestore, CTS, Italy

Nanolime

Advantages

• Good compatibility with calcareous materials

• High durability

• High active surface, reactivity, colloidal stability

and calcium content

• Operator and environmental friendly

Limits:

• Limited in-‐depth effectiveness

• Superficial whitening

• Controversial results & few documented

case studies on stone consolidation

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Research aim

Possible reasons of limited in-‐depth deposition

?? Limited penetration,

back-‐ migration,

fast carbonation,

colloidal stability ??

• Understanding transport and deposition of

nanolime is necessary for improving

its effectiveness

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Substrate: Maastricht Limestone

• Lost of cohesion (e.g. powdering)

• 90-‐95% CaCO

₃

• Model material (unimodal)

• Widely used in Limburg (NL and Belgium)

Materials & Methods

Nanolime: Calosil E25

• Opal alcoholic dispersions of lime

nanoparticles

• Nano to submicron dimension

(<50 to 400nm)

Methods:

• Materials characterization (MIP, XRD, Uv-‐Vis, SEM-‐EDS)

• Transport (absorption-‐drying kinetics)

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Characterization of Maastricht limestone

Moisture transport: Absorption/Drying kinetics of water

MIP XRD

WAC= 1,94 g/cm2_s1/2 ≈ 96/120 h

Step I drying

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Characterization of Nanolime E25

30 mins ultrasonic bath (minimize aggregation phenomena)

Colloidal stability

Stable/homogeneous up to > 1 week

Liquid phase _{Liquid
phase} _Dried

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• Fast absorption (< 5mins):

water faster then EtOH and E25 à differences in the surface tension and viscosity (presence of nanoparticles)

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Transport of nanolime

: drying kinetics

Evaporation rate:

48-‐72h for E25 and EtOH, step I drying ends at 24h: then, transport by vapour, ( à nanoparticles can not be transported anymore)

I stage ≈ 24h

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1. Limited penetration during absorption?

2. Fast carbonation hindering the transport?

Nanolime: cause(s) of limited in-‐depth deposition

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Absorption

1. Limited penetration

during absorption??

Cross section: Phenolphthalein test

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Drying in N₂atmosphere

2. Fast carbonation

hindering the transport?

❌ The distribution of nanolime is similar in N and in air

0.5mm in depth

Drying in air (50% RH, 20o_C)

Drying in N₂atmosphere

8h

24h

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✔

Partial back migration

_{is
the
main
reason
of
the
limited}

Setup

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3. Distribution of nanolimes at different depths

ü Nanoparticles are present in depth --> confim penetration in depth during

absorption.

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3. Transport back to the drying surface

?

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3. Transport back to the drying surface

?

Setup

G. Borsoi, B. Lubelli, R. van Hees, R. Veiga, A. Santos Silva, 2015.

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How to

avoid the back-‐migration

and accumulation at the drying

surface and improve effectiveness?

The transport and deposition of the dispersions should be adapted to

the transport properties of the substrate

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a)

New Nanolime

-‐ colloidal stability and drying rate

Dispersed Ethanol, isopropanol, butanol, water

E25 200 250 300 350 400 450 500 550 600 650 700 0 24 48 72 96 Me an p ar ti cl e si ze (n m ) t (h) B25 E25 IP25 0 10 20 30 40 50 60 70 80 90 100 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 Re la ti ve K in et ic al S ta bi lit y % Time (h) H25 E25 IP25 B25 Uv -‐Vi s DL S 2 weeks 0,5 1 1,5 2 Ev ap or at ed li qu id / A re a (c m 3 /cm 2 ) EtOH_MA IpOH_MA H2O_MA BOH_MA Drying rate

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Depending on the pore networks:

‘Coarse pores’:

moderate (kinetical) stability for a proper absorption, fast

drying rate for a deposition in depth (without nanolime back-‐migration)

‘Thin pores’:

high (kinetical) stability for a proper absorption,

slower drying rate to enhance the deposition of the nanoparticle in

depth.

Solvent properties

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Conclusions

• The main reason of limited in-‐depth deposition of nanolime in coarse porous substrates as Maastricht limestone has been identified in the back-‐migration of nanoparticles during drying.

• The high kinetical stability of nanolime dispersed in ethanol favors the back-‐ migration of nanoparticles in coarse porous substrate

• à Modifying the transport and/or the kinetic stability of nanolimes according to the properties of the substrate might improve the deposition in depth

• The modification of the solvent is a possibility to control transport and kinetic stability of nanolime in order to favour in-‐depth deposition.

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Thanks for your attention!

Barbara Lubelli, Rob van Hees

Rosário Veiga, António Santos Silva

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Publications

Maastricht limestone:

G. Borsoi, B. Lubelli, R. van Hees, R. Veiga, A. Santos Silva, 2015.

Understanding the transport of nanolime consolidants within Maastricht

limestone, Journal of Cultural Heritage, In press,

http://dx.doi.org/10.1016/j.culher.2015.07.014

Lime-‐based mortars:

G. Borsoi, M. Tavares, R. Veiga, A. Santos Silva, 2012. Microstructural

characterization of consolidant products for historical renders: an innovative

nanostructured lime dispersion and a more traditional ethyl silicate limewater

solution, Microscopy & Microanalysis 18, 1181–1189.

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Application methodology:

protocol and strategies

NEXT STEP: OPTIMIZATION OF THE APPLICATION METHODOLOGY

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Synthesis of new nanolime

(bottom-‐up fabrication)

1. ‘Metallic calcium method’

(2006): solvothermal reaction

2. The ‘Baglioni-‐Giorgi-‐Dei method’ (2000) 3. ‘Dispersant method (TX100)’ (2012)

4. ‘Salvadori method’ (2011)

CaCl₂ + NaOH

Deposition of modified nanolimes within calcareous substrates

G. Borsoi, B. Lubelli, R. van Hees, R. Veiga, A. Santos Silva