the combination of calcium hydroxide-sol and silicic...
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DRAFT
12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
1
THE COMBINATION OF CALCIUM HYDROXIDE-SOL AND SILICIC
ACID ESTER AS NEW METHOD FOR THE STRUCTURAL
CONSOLIDATION OF OBJECTS BUILT OF TUFF, LIME MARL, TRACHYTE
– LATEST FINDINGS
Ewa Maryniak-Piaszczynski,1 Verena Wolf1 and Elisabeth Ghaffari2
1 Company: Strotmann & Partner, Restorers, Hauptstr. 140, 53721 Siegburg,
Germany
2 University of Applied Arts Vienna, Institute of Arts and Technology, Section of
Conservation Sciences, Salzgries 14/1, A-1013 Wien, Austria
Abstract
Laboratory investigations concerning the consolidation of flaking and scaling stones
(tuff, trachyte, marl and limestone) show that common testing methods do not give
sufficient information’s when utilised on not weathered materials. New methods had to
be found. Therefore dummy samples (samples of powder, cubic samples, cylindric samples), which simulate deteriorated stone were developed in three years of
investigations within the EU project STONECORE. These samples gave totally new
insights to the structural consolidation of disintegrated stones.
Three different consolidation methods were tested:
- consolidation with silicic acid ester (Funcosil 100 and 300, Remmers, Germany) - consolidation with nanolime: calcium hydroxide nano-particles in different alcohols
(CaLoSiL, IBZ Salzchemie, Germany) - consolidation with a combination of nanolime and silicic acid ester
The efficacy of consolidation treatments was assessed through various methods of
measurements: tensile bending strength, water absorption after 24h, porosity, peeling
test, drilling resistance, X-ray-analyses and microscopic analyses.
The best results gave dummy samples which were first treated with CaLoSiL to consolidate flakes and loose particles and additionally with silicic acid ethylester.
Keywords: stone conservation, consolidation, scales, flakes, silicic acid ester,
nanolime, CaLoSiL, combination of CaLoSiL and silicic acid ester
Introduction
Heritage protected stone monuments show among deterioration patterns like
sanding as well degradation in terms of scaling and flaking. Till this day common
consolidation materials often show unsatisfying results when dealing with those decays.
One example of the inorganic consolidation group is silicic acid ester based on
tetraethoxysilane, which is a very popular material in the field of conservation of stones
and mortars.
CaLoSiL products can offer a new method of consolidation where traditional
materials and techniques fail. Therefore the use of CaLoSiL compounds is desirable especially where silicic acid ester is inappropriate. For example silicic acid ester is in
some cases not able to bridge large spaces which make it unsuitable as consolidant for
flaking and scaling stones. In this kind of deterioration phenomena fillers and adhesives
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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for bridging are required. Nano-lime could be a possible solution. A further alternative
might be a combination of both products (CaLoSiL and silicic acid ester) to utilise their particular advantages for a successful consolidation. Three years of investigations have
been engaged in this topic. This paper presents the most important laboratory results.
Materials and sample preparation
Former consolidation investigations on unweathered materials show insufficient
significant results for praxis relevant application methods. Therefore different kinds of samples were prepared in laboratory which simulates a diversity of stone deterioration.
Figure 1-3. Flaking and sanding stones: Limestone, Marl, Tuff.
Table 1: Range of used materials
Sample shape Crushed
material
Consolidant Short name of
consolidant
Dummy samples Marl Nano-lime: calcium hydroxide in ethanol CaLoSiL
E25
Sandwich samples Limestone Nano-lime: calcium hydroxide in iso-
propanol CaLoSiL
IP25
Cylindrical samples Trachyte Nano-lime: calcium hydroxide in n-propanol CaLoSiL
NP25
Cubic samples Tuff Silicic acid ester Funcosil
100
Silicic acid ester Funcosil
300
Figure 4. Dummy samples
Figure 6. Sandwich samples
Figure 5. Cylindrical samples
Figure 7. Cubic samples
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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On the one hand samples were sole treated with CaLoSiL or Funcosil, on the other hand combinations of both consolidants were tested. Subsequent a set of analysis
were conducted to approve the results.
3. Measurements and analyses on selected samples
The most important investigations and their results are given in the following
section. This includes only a selection of laboratory made samples. However,
applications on real objects and their examinations are not included in this paper.
3.1 X-ray-analyses and mineralogical composition
Scanning electron microscopy and EDAX investigation (Investigations by D. Kirchner, Deutsches Bergbau-Museum Bochum with Pananlytical X
Pert Pro Data Collector – X-Celerator)
Investigation after two weeks of storage at RH 75% X-ray examinations of samples,
which were treated with different combinations of CaLoSiL and Funcosil show a lot of amorphous structures which cannot be clearly identified. The following crystals can
be detected: calcites, portlandites and vaterites. The lower the concentration of
Funcosil the higher is the concentration of calcites, vaterites and calcium hydroxide. EDAX analyses always present chemical structures of silicon and calcium but the
structure changes in each composition.
Investigations show that
CaLoSiL IP25 with heptane,
CaLoSiL E25, CaLoSiL IP25 and
CaLoSiL NP25 build the biggest
amount of calcites, vaterites and portlandites.
Figure 8. X-ray examination of all compounds
X-ray examinations on samples which were treated with CaLoSiL
NP25,
Funcosil 100 and 300 in different variations:
Figure 9. CaLoSiL NP25,
after 24 hrs: Funcosil 100
Figure 10. CaLoSiLNP25,
after 24 hrs: Funcosil 300
Figure 11. All methods
(Grey: Mixture of CaLoSiL
NP25 and Funcosil 100)
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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EDAX investigations and SEM-analyses on samples which were treated with
CaLoSiL NP25, Funcosil 100 and 300 in different variations:
Figure 12 - 14. CaLoSiL NP25, after 24 hrs: Funcosil 100
Figure 15 - 17. CaLoSiL NP25, after 24 hrs: Funcosil 300
Figure 18 - 20. Mixture of CaLoSiL NP25 and Funcosil 100
Treatments with pure CaLoSiL form Ca- minerals: vaterites, calcites and portlandites. In combination with silicic acid ester amorphous structures are built as well.
The lower the concentration of silicic acid ester (Funcosil 100) in combination with
CaLoSiL the more portlandites, calcites and vaterites can be analysed. The bigger the amount of silicic acid ester (Funcosil 300) the less Ca-minerals are formed. In that case,
the amount of amorphous structures decreases.
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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3.2 Physical and mechanical properties dependant on the used consolidant
The change of physical and mechanical properties is shown on examples of marble
samples (fraction of 0 – 2 mm) which were treated with CaLoSiL and Funcosil 100 and 300 in different combinations.
Figure 21. Porosity (vol. %)
Figure 22. Tensile bending strength N/mm2
Figure 23. Water absorption after 24h (w. %)
Figure 24. Compressive strength N/mm²
Control: marble without consolidation
: : : Control: CaLoSiL
25g/l with ethanol , after 6 treatments
Control: only silicic acid ester
1 x CaLoSiL
25g/l with ethanol after 2 h silicic acid ester
6 x CaLoSiL
25g/l with ethanol after 1 day silicic acid
ester
8 x CaLoSiL
25g/l with ethanol after 1 day silicic acid
ester
6 x CaLoSiL
25g/l with ethanol after 6 days silicic acid
ester
6 x CaLoSiL
25g/l in ethanol, first wetted with water
(16%)
Following changes compared to the control sample occur by a treatment with
CaLoSiL and silicic acid ester in combination:
the water absorption decreases
the porosity and the mechanical properties increase
best results show samples with a treatment of CaLoSiL (six times) and after
24 hrs Funcosil 100 and Funcosil
300
the mechanical properties improve
the capillarity does not change much
In general a pre-wetting with water prior to the consolidation shows a positive
influence on the capillary and mechanical properties.
0
5
10
15
20
25
30
Funcosil 100 Funcosil 300
0
0,05
0,1
0,15
0,2
0,25
0,3
Funcosil 100 Funcosil 300
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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3.3 Physical properties dependant on the type of stone
After a pre-consolidation with CaLoSiL E25 (six times) dummy samples of
various kind of stones were treated 24 hrs later eighter with Funcosil 100 or with
Funcosil 300 until saturation (storage for 4 weeks: T 18°C, RH 60%).
Control: only CaLoSiL
: : : Tuff Römer
Tuff Nordhessen
Marl
Gotland sandstone
Baumberger limestone
Carrara marble
Figure 25. Tensile bending strength N/mm² Left: Funcosil 100, right: Funcosil 300
Tuff and marl only show a little increase of the tensile bending strength. A distinct
increase show samples of calcareous stone. The best results achieve calcareous stones
like marble and limestone. In general all samples treated with the combination of
CaLoSiL and Funcosil feature an increase of the tensile bending strength instead of a pure silicic acid ester treatment.
3.4 Drilling resistance on sandwich samples
Sandwich samples of marble which simulate weathered and unweathered stone
were treated with different combinations of CaLoSiL and Funcosil and were stored for six weeks (T 18°C, RH 60%) before drilling resistance tests were investigated.
Figure 26. Drilling resistance measurement [atn]
1 Funcosil 100
2 6 applications of CaLoSiL E25
3 Funcosil 300
4 6 applications of CaLoSiL E25 and Funcosil 100
5 6 applications of CaLoSiL E25 and Funcosil 300
Drilling resistance measurements show that the combination of CaLoSiL and silicic acid ester stabilizes sanding stone. The samples are harder than those which were
consolidated with pure Funcosil 100 and 300 or only with pure CaLoSiL. The best results achieve calcareous stones. Low hardness show samples of tuff,
marl and trachyte. Those results are especially practically important in case of scaling or
0
0 ,0 2
0 ,0 4
0 ,0 6
0 ,0 8
0 ,1
0 ,12
0 ,14
0 ,16
0 ,18
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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flaking stones because the consolidant is able to build bridges between weathered and
unweathered stones.
3.5 Peeling tests (Investigations by ITAM, Czech Republic)
Peeling tests dependant on the consolidation method were made on dummy samples
of marble (fraction of 0 – 2 mm) four months after the treatment.
Figure 27. CaLoSiL E25, Figure 28. CaLoSil E25,
after 24 h: Funcosil 300 after 24h, Funcosil 300
Figures 27 and 28 clearly show better results of a treatment with CaLoSiL E25 and
after 24 hrs with Funcosil 300.
Dependant on the different stone types a treatment with CaLoSiL E25 and
Funcosil 300 achieve the best results: Carrara marble, tuff and Baumberger Limestone. Worse results show marl and trachyte.
Figure 29. Marl Figure 30. Baumberger Limestone
Figure 31. Tuff
Figure 32. Trachyte Figure 33. Carrara marble
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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3.6 Cubic samples: samples of stone powder. Distribution of the consolidants
inside the material
During laboratory tests it was found out that the distribution of the consolidants,
inside a deteriorated stone is one of the most important facts. Therefore special samples
which simulate weathered material were prepared (Idea: Malgorzata Musiela, Company
Restauro). Cubic samples (2 x 4 cm) of different kind of stones with a drill hole in the middle were produced. The holes (6 mm width and 2 cm length) were filled with the
particular stone powder (fraction of 0 – 2 mm) of each stone to simulate deterioration in
practice.
The powder was consolidated with different combinations of CaLoSiL and
Funcosil. The consolidants were applied up to three times with a syringe until the powder was saturated. Afterwards the samples were put into a humid environment at RH
75% for three weeks.
The whole compounds including the natural stone were vacuum-embedded in epoxy
resin (Araldite® 2020). Polished sections were produced perpendicular to the surface of
treatment.
The polished cross sections were coated with carbon and studied by SEM (Philips
XL 30 ESEM, 20 KV, high vacuum, back-scattered electron detector-BSE) fitted with
an energy-dispersive X-ray analyser (Link-ISIS).
The SEM-micrographs taken at low magnification had to be fitted together by use
of Photoshop® in order to cover the whole sample diameter. Pores were edited in pseudo colour (blue, in Figure 34 – 36 white) in order to ease their visibility and to allow a
comparison of the different treatment methods.
Most important goal of the experiment is the verification of the penetration
behaviour of the consolidant. That fact correlates in a penetration of the consolidant in
the deteriorated part of the sample (which is simulated by the powder), a good bonding
between weathered and unweathered area of the stone and nearly no penetration into the
intact part of the sample.
The best effect of consolidation (defined as the recovery of cohesion of loose grains
of disintegrated material) was achieved in most cases if both preparations were used:
CaLoSiL® and then Funcosil®. In case of consolidations with pure Funcosil® further
investigations are necessary because silicic acid ester is not visible in the whole sample although the material was treated until saturation.
Especially in the case of Baumberger Limestone (Figure 34) Funcosil® penetrates
in the intact stone but is not able to bond the loose aggregates. The combination of the
two consolidants remains in the deteriorated part of the stone, it does not penetrate the
intact part. It bonds big and small grains together. This method is suitable for stones that
show deteriorated areas like flaking and scaling up to several centimetres, especially on
tuff, Baumberger limestone and calcareous stones. These results relate to specific types
of stones and mortars. It must be pointed out that each new case requires a preliminary
consolidation trial.
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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Figure 34 - 36. Baumberger Limestone
Left: Funcosil 300
Centre: CaLoSiL E25 and E50
Right: CaLoSiL E25 and Funcosil 300
4. Results and conclusions The results show that a treatment with
CaLoSiL or with a combination of Funcosil is much more successful than a treatment with
pure silicic acid ester.
CaLoSiL is able to bond flakes and scales and to fill the small spaces between
these particles. A following application of
silicic acid ethyl ester gives further stability. The formation of stable bridges between
the particles and the good distribution inside
the stone are absolute advantages of the
combination of CaLoSiL and silicic acid ester.
The consolidation with CaLoSiL was successful, especially on tuff and limestone. It
distributes evenly and bonds large and small
grains together. This method can also be
modified to match the special requirements of each object.
All laboratory and in situ investigations show that a consolidation with CaLoSiL
or with a combination of CaLoSiL and silicic acid ethyl ester allows a stabilization of deteriorated stones.
CaLoSiL products show good adhesion forces and are able to bridge
comparatively large spaces. CaLoSiL forms bridges between the grains and the silicic acid ester adheres to these bridges and to fine grains. The alkaline milieu causes a fast
hydrolysis so that the gel is more stable. Beside calcite, vaterite and portlandite,
amorphous calcium silicate is formed. Stones with high mechanical properties such as
trachyte, marl or calcareous stones should additionally be treated with silicic acid ethyl
ester.
All investigations as well as the method of sample production cause in a better understanding of structural consolidation processes. In this paper introduced results
were already applied on following objects: rectory from XVIII century, cloister (1530):
cathedral of Xanten, citadel Mainz: coat of arms.
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12th International Congress on the Deterioration and Conservation of Stone
Columbia University, New York, 2012
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Figure 37 - 39. Cathedral of Xanten, cloister: conservation on masonry
Acknowledgments
This article is part of the large research project EU-Project: Stonecore 2008-2011,
Contract No. 213651 STONE COnservation for the REfurbishment of buildings,
SEVENTH FRAMEWORK PROGRAMME NMP-Nanosciences, Nanotechnologies,
Materials and new Production Technologies.
References
Busse, H.-B., Egloffstein, P., Gerrecht, H. et al. 2003-2004. ‘Model intentions: Effect of protective constructions (preventive measures) on the weathering of sandstones
due to ecological damage using the example of the north portal of the
Benediktinerabtei Tholey (Saarland)’, Project DBU Az 18636. Mainz, Germany :
Institut für Steinkonservierung.
Maryniak-Piaszczynski, E., Ziegenbalg, G. 2008. ‘The portal in Tholey- unconventional
method for the preservation of scaling and shelled sandstone (Rotliegend-
sandstone)’, Proceedings of the 11th International Congress on Deterioration and
Conservation of Stone, Torun, Poland.
Piaszczynski, E., Wolf, V. 2011. ‘The combination of nano-lime and silicic acid ester
for stone conservation’, Proceedings of the European Workshop on Cultural
Heritage Preservation, Berlin 2011, Fraunhofer IRB:Verlag, 254.
Piaszczynski, E., Ziegenbalg, G. 2010. ‘Nanolime as a binder for injection grouts and repair mortars’, Historic Mortars-HMC and RILRM TC 203-RHM final workshop.