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SWBSS 2017
Fourth International Conference on Salt Weathering of Buildings and Stone Sculptures
20 – 22 September 2017 – Fachhochschule Potsdam
Fourth International Conference on Salt Weathering of Buildings and Stone Sculptures
Programme and abstracts
University of Applied Sciences Potsdam, Germany
20-22 September 2017
Layout: Semler Grafik oHG, Berlin
Cover image: Photo: Hans-Jürgen Schwarz, Design: Benita Lohse
Welcome to Potsdam
Welcome at the University of Applied Sciences in Potsdam!
The first SWBSS event was held in Copenha- gen, Denmark in 2008, with Lisbeth Ottosen as driving force, the second was arranged by Ioannis Ioannou and Magdalini Theodoridou in Limassol, Cyprus, in 2011, and the third SWBSS conference was organized by Hilde De Clercq and colleagues at the Royal Institute for Cultural Heritage in Brussels, Belgium.
This is the fourth conference in the series.
It is a great pleasure to see that SWBSS 2017 has been met with interest from so many dif- ferent countries both in Europe and outside of Europe.
We received around 50 contributions, con- sisting of papers and abstracts and bringing together conservators, restorers, engineers, scientists, young students and experienced researchers.
The success confirms the significance of the SWBSS agenda for the scientific community.
Being aware that salt crystallization is of ma- jor importance in the weathering of porous building materials, I do hope that this confe- rence contribute to an exchange of knowled- ge, create new solutions for the preservation of our cultural heritage and stimulate new research ideas and future collaborations wi- thin this interesting field.
On behalf of the Conference Organizing Committee and the participants I would like to take the opportunity to thank the many reviewers of the Scientific Committee who so generously gave their time to ensure that the papers accepted are of a high quality and re- present a true advance in the state-of-the-art.
Furthermore, I would like to thank Hilde De Clercq, Royal Institute for Cultural He- ritage, Brussels, and my colleagues of Salze im Kulturgut e. V., especially Mike Steiger and Hans-Jürgen Schwarz, for co-organizing this SWBSS conference. Thanks also to the
excursion. And without the help of my col- leagues and the students of our University we could not have organized this internatio- nal conference: thank you all!
Last but not least, I would like to express my deepest gratitude to our sponsor The Deutsche Bundesstiftung Umwelt DBU (Ger- man Federal Environmental Foundation) for supporting the printing of the conference proceedings.
I sincerely hope that you will enjoy SWBSS 2017 and wish you a pleasant stay in Pots- dam!
Steffen Laue Conference Chair
University of Applied Sciences Potsdam Department for Conservation and Restoration
Conference Details
SWBSS 2017
Scientific Committee
De Clercq, Hilde – Royal Institute for Cultural Heritage, Brussels, Belgium
Diaz Gonçalves, Teresa – Laboratório National de Engenharia Civil, Lisboa, Portugal Espinosa-Marzal, Rosa M. – University of Illinois at Urbana-Champaign, USA
Flatt, Robert – ETH Zürich, Switzerland
Hamilton, Andrea – University of Strathclyde, Glasgow, UK Ioannou, Ioannis – University of Cyprus, Nicosia, Cyprus
Laue, Steffen – University of Applied Science Potsdam, Germany Lubelli, Barbara – Delft University of Technology, The Netherlands Ottosen, Lisbeth – Technical University of Denmark, Lyngby, Denmark Siedel, Heiner – Dresden University of Technology, Germany
Steiger, Michael – University of Hamburg, Germany
Török, Ákos – Budapest University of Technology and Economics, Hungary
Vergès-Belmin, Véronique – Laboratoires de Recherche des Monuments Historiques, Champs-sur-Marne, France
Organizing committee
Laue, Steffen – University of Applied Science Potsdam and Salze im Kulturgut e. V.
Steiger, Michael – University of Hamburg and Salze im Kulturgut e. V.
De Clercq, Hilde – Royal Institute for Cultural Heritage, Brussels, Belgium
Sponsored by
The Deutsche Bundesstiftung Umwelt DBU (German Federal Environmental Foundation)
Conference Venue
The conference takes place in the Main Buil- ding (HG) of University of Applied Sciences in Potsdam (UoASP).
Address: Kiepenheuerallee 5, D-14469 Potsdam.
How to get to the UoASP by public transportation
From the main station take either tram 92 to „Kirschallee“ or tram 96 to „Viereckremise“, and get off at „Campus Fachhochschule“ – duration approx. 12-15 min.
Registration
The registration desk is located in the entrance foyer of the Main Building. It opens on Wed- nesday 20th September at 08:00 am and will be open all days during the conference. If you have any questions, please, ask at the regist- ration desk.
Oral presentations
Oral presentations are 15 minutes in length, followed question time for 3 minutes and then 2 minutes to facilitate changeover to the next speaker.
Coffee breaks and Lunches
Refreshments during the coffee breaks are available free of charge for registered partici- pants an the conference venue. Lunch will be offered by the Mensa of the UoAS (self-pay)
Campus of University of Applied Sciences in Potsdam
Internet
WIFI access is provided.
Login WLAN: FHP Guest Username: swbss
password: swbss2017
Excursion
The excursion starts on Thursday 21 Septem- ber, 01:45 pm at the UoASP and we will visit the Park Sanssouci in Potsdam. More infor- mations will be provided during the confe- rence.
Social events
Wednesday, 20 September 2017
05:30 pm – Guided tours to the workshops of the Department of Conservation and Resto- ration 07:00 pm – Evening Reception in the hall of the Main Buildung of UoASP
Thursday, 21 September 2017
07.30 pm – Conference Dinner at the Meierei in Potsdam (see page 42)
Friday, 22 September 2017
06:45 pm – Fair well drink in the Main Buil- ding of UoASP
Proceedings of the conference
A hard cover version of the proceedings can be purchased at the registration desk for 30,-€.
A digital version can be downloaded on www.saltwiki.net
SWBSS 2017 – Program
Tuesday, 19 September 2017
19:00 Come together at Café Heider (self-pay)
Address: Friedrich-Ebert-Str. 29, D-14467 Potsdam (in the city center of Potsdam, close to many hotels)
Wednesday, 20 September 2017
08:00 Registration
09:00 Welcome
Steffen Laue – UoAS Potsdam
Eckehard Binas – President of the UoAS Potsdam
Paul Bellendorf – The Deutsche Bundesstiftung Umwelt DBU (German Federal Environmental Foundation) Salt sources, transport and crystallization
Session chair: Robert Flatt
09:30 Traffic-induced salt deposition on facades M. Auras (Mainz, Germany)
09:50 Wick action in cultural heritage
L. Pel & R. Pishkari (Eindhoven, The Netherlands)
10:10 A preliminary study on dynamic measurement of salt crystallization and deliquescence on a porous material surface using optical microscope M. Abuku, D. Ogura & S. Hokoi (Higashi-Osaka, Japan)
10:30 Coffee break
Measurement techniques and experimental studies Session chair: Andrea Hamilton
11:00 New approaches to assess salt induced decay in building stones J. Dassow, A. Leslie, S. Hild, P. Harkness, L. Naylor & M. Lee (Glasgow, UK) 11:20 Diagnostics and monitoring of moisture and salt in porous materials by
evanescent field dielectrometry C. Riminesi & R. Olmi (Florence, Italy)
SWBSS 2017 – Program
11:40
Determination of the water uptake and drying behavior of masonry using a non-destructive method
A. Stahlbuhk, M. Niermann & M. Steiger (Hamburg, Germany)
12:00 Measurement of salt solution uptake in fired clay brick and identification of solution diffusivity
E. Mizutani, D. Ogura, T. Ishizaki, M. Abuku & J. Sasaki (Kyoto, Japan)
12:20 Lunch
Session chair: Lisbeth Ottosen
13:30 How surfactants affect salt crystallization in sandstones?
M. Qazi, D. Bonn & N. Shahidzadeh (Amsterdam, The Netherlands)
13:50 Local strain measurements during water imbibition in tuffeau polluted by gypsum
M.A. Hassine, K. Beck, X. Brunetaud & M. Al-Mukhtar (Orleans, France) 14:10 Assessment of the durability of lime renders with Phase Change Material
(PCM) additives against salt crystallization
L. Kyriakou, M. Theodoridou & I. Ioannou (Nicosia, Cyprus)
14:30 Poster session (2 min oral presentations of each poster) – see page 36 15:00 Coffee break and poster session
Measurement techniques and experimental studies Session chair: Ioannis Ioannou
16:00 Biogenic hydroxyapatite – a new material for conservation A. Hamilton, R. Turner & J. Renshaw (Glasgow, UK)
16:20 Electrode placement during electro-desalination of NaCl contaminated sandstone – simulating treatment of carved stones
L. M. Ottosen & L. Andersson (Lyngby, Denmark) 16:40
Salt crystallization effect on the protective treated sandstone by SiO2-based and POSS-based hybrids during hygrothermal cycles
M J. Jia, L. He, J Y. Liang and X. Zhao (Xi’an, China)
17:15 Guided tours to the conservation and restoration workshops (UoAS Potsdam)
19:00 Reception at the University of Applied Sciences Potsdam (in the building of the conference)
SWBSS 2017 – Program
Thursday, 21 September 2017 Studies for conservation issues Session chair: Barbara Lubelli
09:00 Efficiency of laboratory produced water repellent treatments on limestone C. Charalambous & I. Ioannou (Nicosia, Cyprus)
09:20
Environmental control for mitigating salt deterioration by sodium sulfate on Motomachi Stone Buddha in Oita prefecture, Japan
K. Kiriyama, S. Wakiya, N. Takatori, D. Ogura, M. Abuku & Y. Kohdzuma (Kyoto, Japan)
09:40 Management of sodium sulfate damage to polychrome stone and buildings D. Thickett & B. Stanley (English Heritage, UK)
10:00 Conservation of marble artifacts by phosphate treatments: Influence of gypsum contamination
E. Sassoni, G. Graziani, E. Franzoni & G.W. Scherer (Bologna, Italy) 10:20 Coffee break
Salt crystallization tests Session chair: Mike Steiger
10:50 Salt crystallization tests: Focus on their objective
E. Charola, I. Rörig-Dalgaard, J. Chwast, J. Elsen & H. Janssen (Washington, DC, US)
11:10 Mitigating salt damage in lime-based mortars with mixed-in crystallization modifiers
S. Granneman, B. Lubelli & R.P.J. van Hees (Delft, The Netherlands)
11:30 Artificial decay of rocks for stone treatments evaluation in laboratory D. Costa (Lisbon, Portugal)
11:50 First results of the RILEM TC 271 ASC – A review of salt crystallization tests B. Lubelli & RILEM TC-ASC working group (Delft, The Netherlands)
12:10 Predicting salt damage in practice: A theoretical insight into laboratory tests
R. Flatt & RILEM TC-ASC working group (Zürich, Switzerland)
12:30 Lunch
13:45 Excursion to the Park Sanssouci
19:30 Conference dinner in the Meierei – Park New Garden
SWBSS 2017 – Program
Friday, 22 September 2017 Studies for conservation issues Session chair: Heiner Siedel
09:00
Combined non-destructive measurements to understand the salt weathering at the Torre de Quintela, Portugal
A. M. Ricardo, W. Wedekind, L.M.O. Sousa & S. Siegesmund (Göttingen, Germany)
09:20 Protecting Pompeii with clay barriers M. Michette & R. Kilian (Oxford, UK)
09:40 How not to bother soluble salts while grouting
C. Pasian, F. Piqué, C. Riminesi & A. Jornet (Lugano, Switzerland) 10:00
Early treatments for porous plaster and salt-damaged wall decorations in Scandinavia
M.C. Christensen, H. Andersson, I. Brajer & P. Klenz Larsen (Lyngby, Denmark) 10:20 Coffee break
Conservation issues and salt reduction Session chair: N.N.
10:50 The application of hydroxyapatite-based treatments to salt-bearing porous limestones: A study on sodium sulphate-contaminated Lecce Stone
G. Graziani, E. Sassoni, G.W. Scherer & E. Franzoni & (Bologna, Italy) 11:10 Moisture transport during poultice application
C. Franzen, M. Aulitzky & S. Pfefferkorn (Dresden, Germany)
11:30 Evaluation of desalination and restoration methods applied in Petra (Jordan)
W. Wedekind & H. Fischer (Göttingen/Berlin, Germany)
11:50 Desalination of Cotta type Elbe sandstone with adapted poultices:
Optimization of poultice mixtures and application terms J. Maitschke & H. Siedel (Potsdam/Dresden, Germany)
12:10 Lunch
Salt reduction and case studies Session chair: Ákos Török
13:20 Salt extraction by poulticing – results of a pre-investigation at the archeological site of Coudenberg
S. Godts, H. De Clercq & M. Rich (Brussels, Belgium)
13:40
Tracing back the origins of sodium sulfate formation on limestone as a consequence of a cleaning campaign: the case study on Charité and Espérance sculptures of Chartres cathedral
S. Benkhalifa, V. Vergès-Belmin, O. Rolland & Leroux Lise (Paris, France)
SWBSS 2017 – Program
14:00 Granite and schist masonry desalination by poultices at Jacobine Church in Morlaix, France
B. Brunet-Imbault, B. Reidiboym & C. Guinamard (Studiolo, Paris, France) 14:20
Investigation of salts sources at the Karadjordje‘s Gate on the Belgrade fortress
M. Franković, N. Novaković, S. Erić, P. Vulić & V. Matović (Belgrade, Serbia) 14:40 Coffee break
Case studies
Session chair: Véronique Vergès-Belmin
15:10
Salt content of dust and its impact on the wall paintings of the church St. Georg at the UNESCO World Heritage site Monastic Island of Reichenau in Germany
J. Frick, M. Reichert, & H. Garrecht (Stuttgart, Germany)
15:30 Investigation and examination of a degraded Egyptian painted limestone relief from Tell Hebua (Sinai)
E. Mertah, M. Othman, M. Abdelrahman, M. Fatoh, S. Connor (Cairo, Egypt) 15:50
Salt-induced flaking of wall paintings at the Mogao Grottoes, China L. Wong, S. Bomin, W. Xiaowei, A. Rava & N. Agnew
(The Getty Conservation Institute, L.A., US)
16:10 Investigation and conservation concept of salt damaged epitaphs in the church of Werben (Saxony-Anhalt)
S. Laue, D. Poerschke & B. Hübner (Potsdam, Germany) 16:40 Closing remarks & Fair well drink
SWBSS 2017 – Program SWBSS 2017 – Abstracts
Wednesday, 20 September 2017
Salt sources, transport and crystallization
Traffic-induced salt deposition on facades
Michael Auras*
Institut für Steinkonservierung e. V., Mainz, Germany
* auras@ifs-mainz.de
Abstract
Air pollution has been reduced significantly in Germany during the last decades. Never- theless high pollution levels are recorded in urban environment along heavy-trafficked roads. Relevant portions of the emissions of nitrogen oxides and fine particulate matter are caused by car traffic. The change of en- vironmental conditions has led to a change of salt deposition on facades. Actual research results show high concentrations of nitrogen oxides at historical facades but contradictory data for the deposition of nitrates. Additio- nally, the redispersion of de-icing salt by car traffic leads to a deposition of chlorides on fa- cades not only in the base zone.
Keywords: Air pollution, traffic emissions, salt input
Wick action in cultural heritage
Leo Pel* and Raheleh Pishkari Eindhoven University of Technology, The Netherlands
* l.pel@tue.nl
Abstract
Salts crystallization is one of the main de- gradation mechanisms of historical objects, e.g., masonry. In this study we looked at a special case often encountered in marine en- vironment, i.e., wick action. This is a steady state situation in which one end of an object is continuously absorbing a salt solution, e.g., sea water, whereas at the same time at other side there is continuous drying. As a result there will be a continuous flux of ions to- wards the drying surface and the concentra- tion at the drying surface will slowly increa- se, resulting eventually in crystallization.
In this study we looked at wick action for a 1m NaCl solution using a biomicritic limes- tone from Sardinia, which is found in many cultural heritage objects. To measure both moisture and salt content simultaneously, we have used a specially designed Nuclear Magnetic Resonance (NMR) set-up. The wick action experiment was performed for over 40 days. The results show that the concentration over 40 days slowly increases at the top until the saturation concentration is reached. It is shown that the concentration profiles can be modelled by a simple analytic solution of the advection-diffusion equation describing the ion transport.
Keywords: Wick action, drying, salt crystalliz- ation, Nuclear Magnetic Resonance
A preliminary study on dynamic measure- ment of salt crystallization and delique- scence on a porous material surface using optical microscope
M. Abuku1,*, D. Ogura2 and S. Hokoi2
1 Faculty of Architecture, Kindai University
2 Graduate School of Engineering, Kyoto University
* abuku@arch.kindai.ac.jp
Abstract
This paper reports on our preliminary attempt to perform dynamic laboratory mea- surements of salt crystallization and subse- quent deliquescence on a surface of a porous material specimen (autoclaved aerated con- crete as a model material) by using a high- resolution digital optical microscope that allows generating three-dimensional images.
A specimen that is initially filled with a NaCl solution is dried in a room at ~ 26°C and
~ 40%RH for 14 days and is then wetted in a desiccator at ~ 95%RH during the next 14 days. A temporal change of the spatial distri- bution of the volume occupied by salt crys- tals on the specimen surface is determined based on the contrast between two microsco- pic images successively taken with a certain
Measurement techniques and experimental studies
SWBSS 2017 – Abstracts
interval of time. The mass of the specimen is also measured simultaneously to determine the rate of water evaporation/absorption. The results show that salt crystallization during drying is not spatially uniform throughout the specimen surface, which likely depends on the spatial distribution of the pore struc- ture in the specimen, and salt crystal deli-
quesces faster near the edges of the specimen than in the centre, which indicates a stron- ger dependency of salt deliquescence on the geometry of the specimen than on the inner pore structure of the specimen.
Keywords: light microscopy, efflorescence, sodium chloride, absorption/desorption
New approaches to assess salt induced decay in building stones
J. Dassow1, A. Leslie2, S. Hild3, P. Harkness4, L. Naylor1, M. Lee1
1 University of Glasgow (School of Geographical and Earth Sciences)
2 Historic Environment Scotland
3 University of Glasgow (School of Physics and Astro- nomy)
4 University of Glasgow (School of Engineering)
Abstract
New approaches to assess stone decay are required to gain a better understanding of the time scale and magnitude of weathering processes. Deciding on the best conservation strategy for historic buildings suffering from salt decay can be challenging, if the state of decay is only investigated on the surface. Our project aims to develop two new minimally or non-invasive techniques that can assess the state of decay of building stones in situ below the surface. The techniques focus on assessing sandstone masonry with an ultra- sonic drilling tool to estimate the structural properties, and a laser interferometer to mea- sure dilation over time.
The laser interferometer can measure con- traction or expansion of a sample on the na- nometre scale. Salt crystallisation in porous systems can be analysed with very high pre- cision under any temperature and humidity condition that enable salt growth. Characte- rising dilation events through precise measu- rement of displacement and event frequency can provide insight on the intensity of decay
up to a depth of 4 cm. This technique drills a hole of 3 mm diameter with less force exer- ted on the sample than conventional drilling techniques; it enables penetration of rocks with compressive strength in excess of 90 MPa. The variation of the power feedback sig- nal during drilling allows the sample’s struc- tural properties, like porosity, to be deduced.
Salt accumulation in the pores can then be located.
These developed techniques provide a more precise identification of salt weathering in building stones, and can be scaled up from the lab to the field. Potentially the devices can be used in situ under site conditions to enable a precise characterisation of the state of decay.
Keywords: building stone decay, ultrasonic drilling, laser interferometry, sandstone weathering
Diagnostics and monitoring of moisture and salt in porous materials by evanescent field dielectrometry
C. Riminesi1,* and R. Olmi2
1 Institute for the Conservation and Valorization of Cultural Heritage (ICVBC), National Research Council, Firenze (IT)
2 Institute of Applied Physics (IFAC), National Research Council, Firenze (IT)
* cristiano.riminesi@cnr.it
Abstract
Moisture and salts are the main causes of
SWBSS 2017 – Abstracts
the detachment of the painted layer, the whi- tening of surfaces due to the crystallization of salts (efflorescence), and the weakening of the cementing binder. Early diagnostics of wa- ter content and detection of the presence of soluble salts inside the material is a key issue for understanding the degradation processes in such kind of materials and for improving their schedule maintenance. In this contribu- tion a non-invasive microwave system based on evanescent field dielectrometry is descri- bed. The method was tested in the laboratory on moistened plaster samples, some of them containing salts at different concentrations.
Measurements on water-saturated and oven- dry samples provide the basis for calibrating the instrument for on-site measurement of masonry structures, wall paintings and con- crete historical buildings too. The obtained results prove the usefulness of the method as a tool for diagnostics and for monitoring the effectiveness and durability of restoring interventions.
Keywords: sub-surface investigation, mois- ture and salt content, dielectrometry, reso- nant technique, SUSI© system, plaster, stone, concrete.
Determination of the water uptake and drying behavior of masonry using a non- destructive method
A. Stahlbuhk*, M. Niermann and M. Steiger
Department of Chemistry, University of Hamburg, Inorganic and Applied Chemistry
* stahlbuhk@chemie.uni-hamburg.de
Abstract
Historic masonry of different types often suffers from various enrichments in surfa- ce and near-surface areas. Salts, atmosphe- ric pollutants and other materials from ex- ternal sources are possible causes for these enrichments which can directly influence the water uptake and drying of the mason- ry. Thus, a compaction of the superficial po- rous network can be expected in the case of crust formation, an enhanced water upta- ke in the case of hygroscopic salts. Both of
effects, possibly provoked by crusts, and ele- vated salt contents, it is of interest to inves- tigate how affected walls behave at a given relative humidity, e.g. threshold values for enhanced water uptake or release influen- ced by salts. The present study reports on a non-destructive chamber method used to investigate the impact of encrustations and salts on the masonry’s behavior concerning drying by determining moisture flow. Advan- tages of the chamber are its easy and non-de- structive application on the masonry using a sealing material that is solely pressed on the wall without leaving residues and the use of harmless water vapor. An investigation of wall paintings in the cloister of the St. Peter Cathedral in Schleswig which in parts suffer from massive yellowish encrustations is pre- sented to demonstrate the promising results obtained with the chamber method.
Keywords: non-destructive method, water uptake and drying, encrustations
Measurement of salt solution uptake in fi- red clay brick and identification of solution diffusivity
E. Mizutani1,*, D. Ogura1, T. Ishizaki2, M. Abuku3 and J. Sasaki2
1 Graduate School of Engineering, Kyoto University, Kyoto, Japan
2 Tohoku University of Art and Design, Yamagata, Japan
3 Faculty of Architecture, Kindai University, Higashi- Osaka, Japan
* be.etu@archi.kyoto-u.ac.jp
Abstract
Salt solution uptake rates in fired clay brick were measured with γ-ray to investigate the influence of salt on solution diffusivity for appropriate numerical analysis of salt solu- tion transfer and crystallization in porous materials. NaCl and Na2SO4 are the main salts confirmed in Hagia Sophia (Aya Sophia Museum), Istanbul, Turkey, and are used in this experiment. We identified solution dif- fusivity as a function of solution content by a numerical analysis of solution transfer. The
take approximately six times longer to attain a steady state than the time needed for pure water to obtain steady state. This was thought to be caused by the viscosity of the dissolved salts and the presence of crystallised salt in the material. We identified solution diffusi- vity by multiplying moisture diffusivity for pure water by a constant to reproduce the measured solution content in the cases where large amounts of efflorescence was observed at the material surface. In the case of a sa- turated solution of Na2SO4, which is conside- red the salt that most frequently precipitates into material, it was necessary to correct the solution diffusivity equation by considering the effect of in-pore salt precipitation.
Keywords: Solution diffusivity, γ-ray attenua- tion, fired clay brick, sodium salts
How surfactants affect salt crystallization in sandstones?
Mohsin Qazi, Daniel Bonn and Noushine Shahidzadeh Van der Waals- Zeeman Institute of Physics, University of Amsterdam, The Netherlands
Abstract
For building materials, historic monuments and statues the crystallization of salts within the porous stones is for a large part respon- sible for their deterioration and breakdown.
The most abundant salt on earth, NaCl, is re- cognized as one of the major players in salt damage. It has been shown in recent studies that in confined spaces, NaCl crystallizes only after reaching high supersaturations1, which increases its potential to cause dama- ge by exerting a crystallisation pressure. In order to mitigate the damage, various reme- dies have been tried, one of which includes the use of crystallisation modifiers2,3. Diffe- rent types of additives are known to modify the crystallisation process of NaCl4. Such mo- difiers can also be utilized to change the pat- tern of crystallization but also to control the location of crystal precipitation.
We present both macroscopic and micros- copic experiments assessing the impact of various types of surfactants (cationic, anionic, and non-ionic) on the kinetics of NaCl crystallization during evaporation of
SWBSS 2017 – Abstracts
aqueous salt solutions. We also study the ef- fect of surfactants on the kinetics of drying of salt solutions in sandstones of different porosities . we show the important role of the porosity combined with the nature of surfac- tant on crystallization. The experiments are done under isothermal conditions at two dif- ferent relative humidities representative of summer and winter conditions. Our results show that the addition of small amounts of cationic and non-ionic surfactants drastical- ly change the kinetics of crystal growth. The latter leads to salt crystallization as a thick crust tightly attached to the surface. This is in sharp contrast with pure salt solutions for which the formation of cauliflower-like structures is observed that can easily be re- moved by brushing.4 In addition, these chan- ges to the crystallization process have a si- gnificant impact on the drying kinetics: the evaporation rate strongly decreases when a thick salt crust is formed. Consequently, the porous materials remain wet for longer time;
this can subsequently induce other types of damage that are potentially harmful for art- works. Our study shows that although surfac- tants are known to improve the spreading/
wetting properties because of their adsorpti- on at interfaces, their use in the conservati- on treatment of stones against salt damage should be done with caution. Depending on the characteristics of the stone, their impact as crystallization modifiers can become more detrimental for salt contaminated porous materials than it is beneficial.
Local strain measurements during water imbibition in tuffeau polluted by gypsum
Mohamed Ahmed Hassine*, Kévin Beck, Xavier Brunetaud and Muzahim Al-Mukhtar
University of Orleans, INSA-CVL, PRISME – EA4229, France
* Mohamed-ahmed.hassine@etu.univ-orleans.fr
Abstract
The research presented in this communi- cation aimed to evaluate the mechanism of spalling generated by mechanical stresses and strains developed due to imbibition and the link with atmospheric pollution genera- ting gypsum in the stone. Tests were carri-
SWBSS 2017 – Abstracts
ed out on a French limestone, called tuffeau.
Local strains were measured using strain gage rosettes during water imbibition in polluted and unpolluted samples. Three ro- settes were placed on a sample at different distances from the surface (1, 4, 7 cm) to mea- sure locally the strain during water infiltra- tion. These rosettes determine the strain in three directions 0°/45°/90°.
Results concerning the behaviour of pollu- ted stone during imbibition are compared to unpolluted stone. Results concerning diffe- rential strains between the surface and the core of the stone due to water infiltration de- monstrate unusual behaviour not restricted to expansion alone: a local contraction zone and expansion zone in each direction sepa- rately for the stone. Pollution by gypsum has an effect on the strain measurements mainly on the first few centimetres of the stone.
Keywords: gypsum, spalling, local strain, imbibition, tuffeau
Assessment of the durability of lime ren- ders with Phase Change Material (PCM) ad- ditives against salt crystallization
L. Kyriakou, M. Theodoridou*, and I. Ioannou
Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus
* mtheodo@ucy.ac.cy
Abstract
Energy consumption in buildings is most- ly associated with the use of heating and cooling systems. Renders with the addition of Phase Change Materials (PCMs) have the ability to absorb and release thermal energy, when the temperature changes accordingly, thus enhancing the thermal comfort and energy efficiency of buildings. Nevertheless, the performance of such renders with traditi- onal binders lacks international experimen- tal data, especially regarding their durability against salt weathering.
This paper focuses on the effect of different percentages of commercial microencapsula- ted powder PCMs on the properties of hyd- rated and hydraulic lime renders, investiga- ting at the same time the durability of the end-products against salt crystallization. The aim is to produce energy efficient and durable
lime-based renders for the upgrading of con- temporary buildings, as well as for conserva- tion purposes.
The modified composites have significant- ly lower thermal conductivity and increased specific heat capacity at 90 days after labo- ratory production, thus confirming the great potential of PCMs in enhancing the thermal performance of the aforementioned renders.
Comparative tests show that the addition of PCMs has an adverse effect on the mecha- nical properties of the renders and a note- worthy reduction of their bulk density. Ne- vertheless, the salt crystallization resistance of the modified renders improves with the percentage of PCM addition, when assessed both quantitatively and qualitatively follo- wing 15 full immersion wetting and drying cycles in Na2SO4 solution.
Keywords: lime, composites, PCMs, salt crys- tallization
Biogenic hydroxyapatite – a new material for conservation.
Andrea Hamilton*, Ronald Turner and Joanna Rens- haw
Department of Civil and Environmental Engineering, University of Strathclyde, UK
* andrea.hamilton@strath.ac.uk
Abstract
Ordinary Portland Cement (OPC) is by weight the world‘s most produced man-made material, and consequently the most used building material. We present for the first time the direct deposition of biogenic hydro- xyapatite onto the surface of OPC, in a syner- gistic process which uses the composition of the cement substrate. The synthesised hydro- xyapatite is very similar to that found in na- ture; having a crystallite size, iron and car- bonate substitution, and a semi-crystalline structure which identify that this biogenic hydroxyapatite is akin to that found in natu- ral bone and tooth enamel. Hydroxyapatites with such a structure are known to be me- chanically stronger and more biocompatible than synthetic or biomimetic hydroxyapatites.
In the built environment, hydroxyapatite coatings have been proposed for the consoli- dation and protection of sculptural materials
SWBSS 2017 – Abstracts
such as marble and limestone, with biogenic hydroxyapatites having reduced solubility in comparison with synthetic apatites. We further identify that in addition to providing a biofilm scaffold for nucleation, the meta- bolic activity of Pseudomonas fluorescens increases the pH of the growth medium to a suitable level for hydroxyapatite forma- tion. The generated ammonia reacts with phosphate in the growth medium, producing ammonium phosphates, which are a precur- sor to the formation of hydroxyapatite under conditions of ambient temperature and pres- sure. Subsequently, this biogenic deposition process takes place in a simple reaction sys- tem under mild chemical conditions, which are cheap and easy to apply to fragile biologi- cal or architectural surfaces.
Electrode placement during electro-desali- nation of NaCl contaminated sandstone - si- mulating treatment of carved stones
Lisbeth M. Ottosen*, Lovisa C.H. Andersson
Department of Civil Engineering, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
* LO@byg.dtu.dk
Abstract
Carved stone sculptures and ornaments can be severely damaged by salt induced decay.
Often the irregular surfaces are decomposed, and the artwork is lost. The present paper is an experimental investigation on the possi- bility for using electro-desalination for treat- ment of stone with irregular shape with only two electrodes. The used Gotland sandstones were contaminated by NaCl in the laboratory.
Due to the relatively good homogeneity in in- itial salt concentration obtained in this way, interpretation of the ED process were direct.
Stones with an up-side-down T-shape formed the core of the investigation. Electro-desali- nation experiments were made with diffe- rent duration to follow the progress. Success- ful desalination of the whole stone piece was obtained, showing that also parts not being placed directly between the electrodes were desalinated. This is important in case of salt damaged carved stones, where the most fra-
sest to the electrodes and slowest in the part, which was not placed directly between the electrodes. This is important to incorporate in the monitoring program to decide when a desalination action is finished.
Keywords: Electro-desalination, sandstone, carved stone, NaCl
Salt crystallization effect on the protec- tive treated sandstone by SiO2-based and POSS-based hybrids during hygrothermal cycles
M. J. Jia, L. He*, J. Y. Liang and X. Zhao
Department of Chemistry, School of Science, Xi’an Jiao- tong University, Xi’an 710049, China
Abstract
This paper explores the protective perfor- mance of five hybrids to the sandstone by loading NaCl, Na2SO4 and NaCl-Na2SO4 salt solutions during the thermal-humidity cy- cles. Two SiO2-based hybrids of SiO2-g-PMMA- b-P12FMA and hydrolyzed Me2Si(OMe)2/SiO2, and three POSS-based hybrids of POSS-PM- MA-b-P12FMA, POSS-PMMA-b-P(MA-POSS) and PDMS-b-PMMA-b-P(MA-POSS), are de- signed in our previous researches for stone conservation. The results indicate that the stones treated by five hybrids have obvious salt-resistance. But, due to the different salt crystallization behaviors of the small squa- re crystals formed by NaCl solution and the long tabular prismatic crystals formed by Na2SO4 solution, there is still some salt-de- duced damage confirmed as the order of NaCl-Na2SO4>Na2SO4>NaCl. Comparatively, SiO2-g-PMMA-b-P12FMA has showed the best protective performance without any in NaCl-loaded and Na2SO4-loaded cycles, and only a little mass loss in NaCl-Na2SO4 loaded cycles, followed by hydrolyzed Me2Si(OMe)2/ SiO2. However, the treated stones by three POSS-based hybrids only passed NaCl salt cycles, but could not give enough protecti- on in the Na2SO4 and mixed salt cycles. The weathering behavior for untreated stone and treated stone by hydrolyzed MeSi(OMe)/SiO
SWBSS 2017 – Abstracts
powder. While the treated stones by POSS-ba- sed hybrids are occurred cracks first and then spread over the whole body. It is possible to suggest that two SiO2-based hybrids perform much better protection than three POSS-ba- sed hybrids.
Keywords: Hybrids; Protective performance;
Salt crystallization behavior; Hygrothermal cycles.
SWBSS 2017 – Abstracts
Thursday, 21 September 2017 Studies for conservation issues
Efficiency of laboratory produced water re- pellent treatmets on limestone
C. Charalambous and I. Ioannou*
Department of Civil and Environmental Engineering, University of Cyprus, Cyprus
* Corresponding author
Abstract
A number of cultural and architectural he- ritage structures all over the world are built with natural stone. Although this material is considered to be one of the most durable geomaterials, many existing stone buildings and monuments show clear evidence of decay and weathering. The deterioration of stone is strongly related to the presence and mo- vement of water within its pore network. Th- erefore, hydrophobic surface treatments are usually adopted to protect existing or new stonework. Such treatments, however, should not affect the breathability of stone; else, the- re is a risk of enhancing possible decay me- chanisms, such as salt crystallization.
Natural limestones appear to have a degree of inherent water repellency. This has been confirmed through multiple measurements of capillary absorption at different tempera- tures, using water and organic liquids. The measurements were carried out on several building and decorative limestones, showing in each case an anomalously low water sorpti- vity. This natural water repellency of limesto- nes was attributed to the presence of organic contaminants, such as fatty acids, in the pore network of the materials under investigation.
In this paper, the natural water repellency of Cypriot limestones is exploited to develop several water repellent surface treatments, based on oleic acid. The aforementioned labo- ratory produced treatments were applied on a Cypriot calcarenite with proven poor dura- bility characteristics. The results suggest that all treatments can permanently reduce the wettability of the stone under investigation, without modifying its composition or appe- arance.
In order to investigate the durability of the treated stone, wetting/drying cycles were per- formed. The results provide strong evidence that treatment with oleic acid positively af- fects the durability of the stone under study.
Consequently, the aforementioned surface treatment may be potentially used in practice to protect stone facades in buildings and cul- tural heritage sites.
Keywords: Limestone, Oleic Acid, Water Repellency, Wetting, Drying
Environmental control for mitigating salt deterioration by sodium sulfate on Moto- machi Stone Buddha in Oita prefecture, Japan
K. Kiriyama 1,*, S. Wakiya2, N. Takatori1, D. Ogura1, M.
Abuku3 and Y. Kohdzuma2
1 Kyoto University, Japan
2 Nara National Research Institute for Cultural Properties, Japan
3 Kindai University, Japan
* kiriyama.kyoko.24n@st.kyoto-u.ac.jp
Abstract
This study aimed to develop an appropriate interior environment to mitigate the deteri- oration by sodium sulfate crystallization on Motomachi Stone Buddha in Oita prefecture of Japan. This Stone Buddha is carved on the fragile welded tuff and has been covered by a shelter for the preservation. On this site, salt crystallization, especially in winter, is a ma- jor deterioration factor of this Buddha. In pre- vious studies, the crystallization of sodium sulfate and calcium sulfate were identified by XRD. The temperature and relative humidity were measured both indoor and outdoor. Wa- ter quantity analysis of the groundwater near the Stone Buddha has been conducted revea- ling a higher solute content near the Buddha than in the general groundwater in Japan.
According to the temperature and humidity
SWBSS 2017 – Abstracts
measured inside the shelter in winter, it was suggested that the solubility of sodium sulfa- te decreased greatly with dropping in interior temperature and phase change from mirabi- lite to thenardite (sodium sulfate anhydrate) caused the deterioration of the statue. Hence, the shelter was improved to reduce ventila- tion frequency and block the direct solar ra- diation in order to reduce evaporation and decreasing interior temperature in winter. In this study, we have conducted environmental research and salt crystallization experiments under controlled temperature and relative humidity to assess the improvements of the shelter. After improvements of the shelter, the indoor temperature and relative humidi- ty increased in winter. According to our ex- perimental results, the deterioration of the Stone Buddha is reduced highlighting the efficiency of the improvements.
Keywords: Salt Deterioration, Sodium Sulfate, Shelter
Management of sodium sulfate damage to polychrome stone and buildings
David Thickett* and Bethan Stanley English Heritage
* david.thickett@english-heritage.org.uk
Abstract
English Heritage holds large collections of polychrome stone. Often the polychromy only remains as small fragments, loosely adhered to the stone surface with any origi- nal binders having converted to oxalate. The sixteenth century limestone Thetford Tomb fragments are amongst the most significant part of the collection. Salt analyses indicated very high concentrations of sodium sulfate present, (up to 1.5% by mass of the stone). Con- sidering the very fragile nature of the remai- ning polychromy and the aggressive nature of this salt, strict preventive conservation is needed to ensure survival of the informati- on. Theoretically, keeping the RH below the thenardite transition line (the RH is tempera- ture dependant) should avoid any damaging salt transitions. Monitoring with acoustic emission in the storage environment, provi- ded a direct tracing of salt transitions. When
plotted against temperature, it became clear that transitions were occurring at between 3 and 7% lower RH than expected from theory.
Tests with pure sodium sulfate powder coin- cided with the theoretical values. The most likely reason is the effect of the pore struc- ture, particularly fine pores. The values are consistent for a single piece of stone and vary between pieces. A good correlation was ob- served between acoustic emission events and small pieces appearing on the imaging plate of a prototype particle deposition analyser.
Loss of material from two interior building surfaces was monitored using a similar auto- mated camera system. Inspection of the en- vironmental data when material fell, shows similar depression of the RH below the theo- retical values for sodium sulfate.
Keywords: Sodium sulfate, polychromy, acoustic emission, image analysis, preventive conservation
Conservation of marble artifacts by phos- phate treatments: Influence of gypsum con- tamination
E. Sassoni1,*, G. Graziani1, E. Franzoni1, and G. W.
Scherer2
1 Dept. of Civil, Chemical, Environmental and Mate- rials Engineering (DICAM), University of Bologna, Italy
2 Dept. of Civil and Environmental Engineering (CEE), Princeton University, Princeton (NJ), USA
* enrico.sassoni2@unibo.it
Abstract
The use of ammonium phosphate solutions has proven to be very promising for protec- tion and conservation of marble. However, all the studies carried out so far have been performed on uncontaminated marble. Un- fortunately, this is rarely the case in the field, because marble artifacts exposed outdoors are often affected by sulfation, i.e. formati- on of a gypsum crust on the surface. Because gypsum is much more soluble than calcite, the outcome of the ammonium phosphate treatment is expected to be sensibly alte- red by the presence of gypsum. Therefore, in this study the nature and morphology of the new calcium phosphate phases formed
SWBSS 2017 – Abstracts
by reacting gypsum with aqueous solutions of diammonium hydrogen phosphate (DAP) were investigated. In particular, the effect of DAP concentration, ethanol addition (aimed at reducing gypsum solubility), and pH were explored. The result is that phase formati- on can be controlled by suitably tuning the above mentioned parameters. Phases with low solubility (such as tricalcium phosphate and hydroxyapatite) can be obtained by in- creasing the ethanol concentration, the DAP concentration or the pH. However, their for-
mation is associated with diffused cracking, likely because of excessive growth of the new phases. Among the investigated formula- tions, treatment with a 0.1 M DAP solution with 30 vol% ethanol at pH=8 seems to be the most suitable one, as it leads to formation of brushite (about 30 times less soluble than gypsum), without cracking, so that a reduc- tion in gypsum solubility in rain is expected.
Keywords: Marble; Gypsum; Black crusts;
Hydroxyapatite; Protection
Salt crystallization tests
Salt crystallization tests: Focus on their objective
A. Elena Charola1,*, Inge Rörig-Dalgaard2, Jacek Chwast3 and Jan Elsen3
1 Museum Conservation Institute, Smithsonian Insti- tution, Washington, DC, USA
2 DTU, Department of Civil Engineering, Group of Construction Materials, Lyngby, Denmark
3 KU Leuven, Department of Earth and Environmental Sciences, Leuven, Belgium
* charolaa@si.edu
Abstract
Many factors influence the durability of a building material, such as its mechanical resistance, exposure conditions and the pre- sence of soluble salts in it. Since the latter interact with each other, it is difficult to rela- te any of them to the specific damage obser- ved. Lubelli et al.1 have recently summarized the shortcoming of some salt crystallization tests and of the mathematical models based on the accepted salt crystallization theories.
The net result is that there is no single salt crystallization test that can provide all ans- wers since crystallization kinetics, depending on specific circumstances, play a critical role in the induced deterioration. Nonetheless, specific tests have been developed which have proved to be practically viable in as- sessing particular material compatibility or potential damaging sources. Two such tests are described, one using sodium chloride to determine compatibility of restoration mort-
lead to the conclusion that salt tests should be designed for specific objectives.
Keywords: sodium chloride test, sodium sul- fate test, masonry materials, crystallization kinetics
Mitigating salt damage in lime-based mort- ars with mixed-in crystallization modifiers
Sanne J. C. Granneman1, Barbara Lubelli1,* and Rob P. J. van Hees1,2
1 Delft University of Technology, Delft, The Nether- lands
2 TNO Technical Sciences, Delft, The Netherlands
*B.Lubelli@tudelft.nl
Abstract
This paper presents the most important re- sults of a research project which focused on the use of crystallization modifiers mixed in lime mortar to mitigate salt crystallization damage. The research focused on two of the most damaging salts, sodium chloride and sodium sulfate, and suitable crystallization modifiers (sodium ferrocyanide and borax).
We report the major findings related to the effectiveness of the modifiers when mixed in the mortar, and the results of characterizati- on of the additivated mortars in comparison with reference mortars. Moreover, the dura- bility of the developed mortars to salt decay is discussed, based on the results of an ac- celerated salt weathering test carried out in
SWBSS 2017 – Abstracts
plication of crystallization modifiers in resto- ration mortars. Additionally, the mortars with mixed-in modifiers showed a consider- able improvement of the salt resistance when compared to reference mortars. Considering these results an outlook for future research pathways is given.
Keywords: Crystallization modifiers, self- healing, lime mortar
Artificial decay of rocks for stone treat- ments evaluation in laboratory
Dória Costa
National Laboratory for Civil Engineering drcosta@lnec.pt
Abstract
The study of conservation treatments on laboratory requires the use of materials si- milar to those present on the monument.
Sampling is always very limited and almost always insufficient to obtain materials to be tested in laboratory. Very often, the use of quarry materials with a different state of al- teration, when compared with those present in the monument, is the common practice.
To obviate this difficulty an alternative is the preparation of specimens using laborato- ry artificially tests “to age” stone materials.
Freeze and thaw, crystallization of salts, ther- mal or thermal shock or can be used to ob- tain damaged specimens. The choice depends on the original characteristics of the materi- als and quite often determined by the need to obtain rapid transformation of the materi- al that is available. However, where salts are the proven agent of damage, it seems reaso- nable to recommend that the preparation of these artificially aged samples should be made using the same action that is effective in practice.
Weathered surfaces present on monuments are generally heterogeneous, showing profi- les where the outermost zone is more altered than the inner part. For this reason, the pro- tocol of testing should also be able to provide specimens that can simulate these characte- ristics.
Salt crystallization test has a long tradition of use to access the stone durability to salts.
sodium sulphate. It is a very aggressive test, able to produce damage on porous materials, in particular in very porous stones. However, low porosity materials (less than 5% porosity) like granites, are excluded.
The protocol used in this research includes also an “impregnation step” repeated several times before “desalination”. Samples are imp- regnated at 40ºC, placed in a climatic cham- ber (or equivalent) at 5-10ºC for 30-60 minu- tes and then dried at 40ºC, in a ventilated oven, for about 24h. However, the protocol is not universal and must be tested and evalua- ted previously on a non-tested variety.
The test performed on granites used a 10%
sodium sulphate solution concentration but other concentrations can be used, depending on the stone type characteristics and its vul- nerability to salt damage.
Physical changes, like porosity, water ab- sorption by capillarity and mechanical re- sistance of the materials were used to cha- racterize and compare the materials after damage. Depending on the type of material (“porous” or “fissured“ type) drilling resistan- ce or ultrasonic pulse velocity are recommen- ded. On fissured rocks, like granites, ultraso- nic methods (“ultrasonic pulsed velocity”
- UPV) are considered very sensitive, allowing the detection of salt effect and presence, par- ticularly in laboratory conditions. Drilling resistance used on limestones allows evalua- ting the hardness in depth. The interpretati- on of the profiles must considered the two possible effects; strength increase due to the presence of salt or its decrease due to the da- mage promoted by them, evident after des- alination.
Keywords: salt crystallization test, drilling resistance, ultrasonic pulse velocity, natural stone
First results of the RILEM TC 271 ASC – A review of salt crystallization tests
Barbara Lubelli1,* and RILEM TC 271 ASC working group
1 Delft University of Technology, Delft, The Nether- lands
* B.Lubelli@tudelft.nl
Abstract
The durability of building materials with
SWBSS 2017 – Abstracts
An effective laboratory ageing test should assess, in a reliable way and within a rea- sonable period of time, the durability and, especially when the conservation of historic buildings is concerned, the compatibility of a material in practice. However, existing (stan- dard) crystallization test procedures do not generally reproduce solution transport and salt crystallization processes realistically.
This may result in damage types that are dif- ferent from those known from practice for the material concerned.
The literature on this subject shows the re- luctance of researchers to use standard tests.
The use of different procedures hinders the comparison between the results of different studies. Moreover, none of the existing stan- dards prescribes an objective, quantitative and reliable method for monitoring the da- mage. Another limit of current standard salt crystallization tests consists in the scarce va- lidation of the results from the accelerated test through comparison with field data, for factors such as damage type and severity.1
The RILEM Technical Committee 271 ASC2, initiated in 2016, aims at overcoming the above-mentioned limitations by the develop- ment of improved test procedures for the as- sessment of the behaviour of materials with respect to salt crystallization.
An extensive literature review of laboratory tests is one of the first outcomes of the ongo- ing work of the RILEM TC 271-ASC. The review provides an overview of existing procedures (standard and not) and identifies their advan- tages and limitations.
The following variables are considered in the literature review:
- Specimen type, shape, size, number of repli- cates, etc.
- Salt type and amount
- Salt contamination procedure - Drying conditions
- Methods for the assessment of the damage and criteria of evaluation of the decay
Based on the review, improved ideas are provided for the development of effective salt crystallization procedures.
References
1 B. Lubelli, R.P.J. van Hees, T.G. Nijland, Salt crystallization damage: How realistic are existing ageing tests? In: Proc. 3rd Int. Conf.
Salt Weathering of Buildings and Stone
Sculptures SWBSS 2014 (Ed. H. De Clercq) Brussels: KIK-IRPA, 2014, 259-273.
2 https://www.rilem.net/groupe/271-asc-ac- celerated-laboratory-test-for-the-assess- ment-of-the-durability-of-materials-with-re- spect-to-salt-crystallization-355 (retrieved on September 10, 2017).
Predicting salt damage in practice: A theo- retical insight into laboratory tests
Robert J. Flatt1,*, Nevin Aly Mohamed2, Francesco Caruso3, Hannelore Derluyn4, Julie Desarnaud5, Ro- ald Hayen6, Barbara Lubelli7, Rosa Maria Espinosa Marzal8, Leo Pel9, Carlos Rodriguez-Navarro10, George W. Scherer11, Noushine Shahidzadeh12 and Michael Steiger13
1 ETH Zurich, Switzerland, 2 Suez University, Egypt,
3 University of Oslo, Norway, 4 University of Pau, Fran- ce, 5 The Getty Institute, USA, 6 Royal Institute for Cul- tural Heritage, Belgium, 7 TU Delft, The Netherlands
8 University of Illinois at Urbana Champaign, USA, 9 Uni- versity of Eindhoven, The Netherlands, 10 Universtiy of Granada, Spain, 11 Princeton University, 12 Univer- sity of Amsterdam, The Netherlands, 13 University of Hamburg, Germany
Abstract
Salt crystallization is accepted to represent one of the major causes for the degradation of building and ornamental stone. As such, it has attracted the attention of researchers, who over the years have progressively unra- veled most mechanisms involved in salt da- mage. Despite this, many questions subsist about how to quantitatively predict damage or its progression, and in particular how to relate performance on site to that in labora- tory tests.
In this context, a new RILEM TC has been started with the objective of defining labora- tory tests that deliver more reliable predic- tions of field behavior. One deliverable of this TC, is to provide a theoretical insight into this question based on recent progress on the understanding of salt damage. This paper presents a summary of this work, highligh- ting key aspects relating to crystallization pressure, chemo-mechanics and transport.
Implications are more specifically discussed in relation to existing accelerated tests in an attempt to better define the type of field ex- posure that they may best represent.
SWBSS 2017 – Abstracts
Friday, 22 September 2017 Studies for conservation issues
Combined non-destructive measurements to understand the salt weathering at the Torre de Quintela, Portugal
Menezes A. Ricardo1,*, Wanja Wedekind2, L. M. O.
Sousa3 and Siegfried Siegesmund1
1 Georg-August University Goettingen, Germany
2 Applied Conservation Science (ACS) Goettingen/Ber- lin, Germany
3 Universidade de Trás-os-Montes, Vila Real, Portugal
*amandamricardo@gmail.com
Abstract
The Middle Age tower in this study is loca- ted in a small village in the region of Quinte- la, north of Portugal, from which the tower also receives its name. This building is part of a simple agricultural area near the Alvão Mountains that has been standing since the 11th Century. The Quintela Tower exhibits a prismatic format with dimensions of 8.6 m x 10.5 m x 18 m and is built from different types of granite. The interior is divided into three floors.
Three main types of granites are used on the façade of this building, and they can be classified as leucocratic, phaneritic, in- equigranular, with subhedral crystals and grain sizes varying from coarse, medium to fine. The most common weathering forms are efflorescence, back-weathering, coloring, fractures and biological colonization.
The main cause for the back-weathering evident on the Quintela Tower might be rela- ted to the behavior of salts crystallizing near and under the surface of the granites. Crys- tallization of a supersaturated solution can provide sufficient crystallization pressure to cause several ruptures on the stones.
To understand the state of decay by salt weathering, combined non-destructive mea- surements and acquisitions were applied.
The measuring procedure consisted of three measurements from the same point in the middle of the stone blocks, using a simple moisture measuring device of the brand GE Portimeter. The open porosity was checked by measuring the water uptake using test-pi-
pes. The different granite lithotypes as well as the damages were mapped and quantified.
This measuring equipment allows the moisture level to be determined by measu- ring the capacity, the dry conductivity and the wet conductivity. For the first two measu- rements the equipment is placed against the surface of the ashlar. For wet conductivity, however, sterilized cotton pads are used and moisturized with 5 ml of distilled water. They are then placed on the stone blocks for thirty seconds and the conductivity measured over the pad.
In total 1,355 measurements were taken on the tower. Outside the tower 728 measure- ments were obtained (182 per each one of the four sides) up to the same maximum reacha- ble level, and inside 627 were done, where 375 were taken on the first floor, 132 on the se- cond floor and 120 on the third and last floor.
Generally, conductivity is higher when the wet cotton pads are used and shows so- metimes different results comparing to the dry performed measurements. This can be traced back to soluble but not hygroscopic salts. Moreover, the measurements show dif- ferent results according to the orientation of the four façades of the tower. This can be tra- ced back to, not only the main wind and rain direction, but also to the sun incident angle and the environmental conditions (moisture) throughout the years and other features dis- cussed in this study.
Keywords: Non-destructive measurements, salt weathering, Torre de Quintela
Protecting Pompeii with clay barriers
Martin Michette1 and Ralf Kilian2
1 University of Oxford, School of Geography, UK
2 Fraunhofer-Institut für Bauphysik, Valley, Germany
Abstract
The project will identify local soils from the Pompeii region for use in protecting the ar- chaeological sites from ground moisture. Sui-
