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Restoration and preservation of the reinforced concrete poles of fence at the former Auschwitz concentration camp

(in lingua inglese)

A number of reinforced concrete pillars present on the area of former Auschwitz concentration and extermination camp call for restoration due to their significant degradation following 70 years of atmospheric exposure. The pillars, which were subjected to repair 10 years ago reveal deficiencies in applied restoration exemplified as cracking between original concrete part of the pillar and the fresh mortar applied during the restoration. The possible reasons of the interfacial cracking between original and new concrete layers are: shrinkage of mortar upon settlement or more probably corrosion process occurring on the reinforcement causing the concrete to crack.

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Articoli tecnico scientifici o articoli contenenti case history
Articolo Case Studies in Construction Materials, 2015

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da Alessia De Giosa




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Case study Restoration and preservation of the reinforced concrete poles
of fence at the former Auschwitz concentration and
extermination camp A. Miszczyk*, M. Szocinski, K. Darowicki Gdansk University of Technology, Chemical Faculty, Department of Electrochemistry, Corrosion and Materials Engineering, 11/12
Narutowicza Street, 80-809 Gdansk, Poland A R T I C L E I N F O Article history:
Received 28 October 2015
Received in revised form 1 December 2015
Accepted 3 December 2015
Available online 14 December 2015 Keywords:
Concrete renovation
Cultural heritage
Sacri ficial protection Rebar corrosion A B S T R A C T The objective of this study was to assess the present state of the reinforced concrete poles of
fence at the former Auschwitz I and Auschwitz II-Birkenau concentration and
extermination camp. The poles were subjected to renovation about 10 years ago. After
this time some de ficiencies of applied renovation method were noticed. Cracks appeared between fresh and original part of concrete cover. Analysis of the reasons of these failures
was performed and a modi fication of used restoration method was proposed to overcome this de ficiency. The modification consists in application of sacrificial anodes mounted outside the pole, in soil and inside the concrete cover. ã 2015 The Authors. Published by Elsevier Ltd. All rights reserved. 1. Introduction Fences, consisting of concrete poles and barbed wire are a visual symbol of death camps created during World War II by Nazi Germany (Fig. 1). KL Auschwitz was the largest of the concentration and extermination camps. This memorial for the
tragic events of World War II and a symbol of the Holocaust and Nazi German crimes is a warning to the world and should be
preserved as intact as possible for the future generations. This area is now the Auschwitz-Birkenau State Museum, which is
visited annually by over 1.5 million people from all over the world (Auschwitz Report, 2014). The museum consists of two
distinct areas: Auschwitz I (the older part, founded in 1940) and Auschwitz II-Birkenau (founded in 1942), located at a
distance of about 3 km from each other and situated in or near the town Oswiecim. The whole area of the former camp
Auschwitz is ca. 200 ha. This area was surrounded and divided by a fencing system, which has been connected to the
electrical high voltage and guarded by sentries on the watchtowers (Swiebodzka, 2008). After more than 70 years of
exposure the former concentration and extermination camps Auschwitz I and Auschwitz II-Birkenau, need assessment of the
current state of buildings, ruins and other elements included in order to undertake the necessary comprehensive
maintenance. In particular, this applies to the reinforced concrete poles of fences. A comprehensive and systematic approach
to their renovation to prevent progressive degradation was undertaken at the end of the twentieth century (Swiebodzka,
2008). As the aim was to restore them using the principles of minimum necessary intervention, they were dif ficult to perform and required the participation of many people with different specializations. About 3000 poles were renovated.
Currently, it has been over 10 years since the completion of this work. It was decided to review the status of these poles to
gather experience and possibly correct methods used. There are still poles requiring renovation (Fig. 2). * Corresponding author. Fax: +48 58 3471092. E-mail address: andrzej.miszczyk@pg.gda.pl (A. Miszczyk). http://dx.doi.org/10.1016/j.cscm.2015.12.002
2214-5095/ ã 2015 The Authors. Published by Elsevier Ltd. All rights reserved. Case Studies in Construction Materials 4 (2016) 42 ''48 Contents lists available at ScienceDirect Case Studies in Construction Materials j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c s c m 2. Mechanism of destruction The results of conducted study showed that the primary cause of the destruction of the reinforced concrete poles is the process of carbonation and high humidity of environment due to high levels of groundwater. As a result of these phenomena,
the environment of the concrete cover becomes close to neutral, which leads to corrosion of steel reinforcement (Ann et al.,
2010; Bartolini et al., 2013; Nguyen et al., 2015; Crevello et al., 2015). Because steel corrosion products occupy several times
larger volume (up to 6 times (Jaffer and Hansson, 2009)) than consumed steel, disintegrating stresses arise which cause
cracks and the loosening of concrete cover (Fig. 3). It has been found that the presence of adverse ions (chlorides, sulfates) in
the environment was minor and did not affect the degradation process. 3. Used method of restoration and preservation There is scarcity of the repair methods of historic reinforced concrete structures damaged by carbonation inducted corrosion (Mietz, 1995; Bertolini et al., 2008; Zheng et al., 2012; Mosoarca and Victor, 2013; Franzoni et al., 2014; Pagliolico
et al., 2014). The approach selected for restoration and preservation of the reinforced concrete pillars consisted in cleaning of
the exposed bare reinforcement from corrosion products using abrasive methods. Then such prepared rebar was protected [(Fig._1)TD$IG] Fig. 1. A fragment of fence and barrack in the former Auschwitz II ''Birkenau. [(Fig._2)TD$IG] Fig. 2. Some poles need still renovation. A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48 43 with an organic coating and finally the missing concrete layer was substituted with a fresh mortar. Fig. 4 illustrates an exemplary pillar restored using the above technology. Unfortunately, after 10 years of atmospheric exposure most of the
renovated pillars have experienced degradation in form of cracks. The cracks run along the interface between original
concrete and the part of the mortar applied during the renovation (Figs. 4 and 5). The first suspicion on possible reason of this degradation was disbonding between the original and new part of concrete due to signi ficant shrinkage of fresh mortar. It created the stress, which occurred to be signi ficant enough to overcome interfacial adhesion between old and repaired part of concrete. However, the fact that the cracks had not formed within the period of time directly following restoration did not
support this assumption. Thus, the most probable scenario was degradation due to renewed corrosion of steel reinforcement
according to the mechanism described in Section 2. The small amount of mortar used for the restoration did not change
signi ficantly the environment of concrete cover to passivate bare steel and after about 10 years of service life of coatings applied on steel rebar a protection has finished. Also the mortar used for the restoration suffered from carbonation over time and the organic coating applied on the reinforcement during renovation no longer provided anticorrosion protection. Hence,
corrosion products build-up caused concrete cracking due to the formation of corrosion products on a much larger volume
than the consumed steel. Probability of this scenario is supported by the fact that in all cases the cracks appear at the side of
the pillar where the rebar is located (closer to steel rebar). In the case of shrinkage different location of crack with respect to
joints will be justi fied. 4. Suggested modi fication of the used methods In order to help that situation and prevent that type of pillar degradation the authors propose a modi fication to the applied protection method. The modi fication involves utilization of cathodic protection system with sacrificial (galvanic) anodes (Wilson et al., 2013; Redaelli et al., 2014). It is an electrochemical approach, in which steel structure to be protected is [(Fig._3)TD$IG] Fig. 3. Mechanism of destruction of reinforcing steel bars embedded in concrete due carbonation process. [(Fig._4)TD$IG] Fig. 4. Reinforced concrete pillar subjected to repair in 2004. The red arrow indicates the crack and the blue rectangle the new mortar. (For interpretation of
the references to color in this figure legend, the reader is referred to the web version of this article). 44 A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48 electrically connected with more active electrode (named sacri ficial anode or protector), which exhibits lower electrochemical potential than the protected element. In this way an electrochemical cell is formed and it is the protector
that corrodes and thus protects the structure. This solution requires periodical replacement of the consumable protector.
Magnesium or zinc sacri ficial anodes are used in soil environment for steel protection. In order to ensure effective protection of steel reinforced pillar two variants of protection are suggested. The first one consists in placing the protector in ground in vicinity of the reinforced concrete pillar as illustrated in Fig. 6a . Electrical
connection between the protector and the steel reinforcement is accomplished in the underground section of the pillar, so
the protection system is not visible for the potential visitors, which ful fills the requirements for conservation of historical heritage objects. The same requirement is ful filled by the second variant of protection, which predicts positioning of the protector directly on the reinforcement (Fig. 6b). In this case the protector is typically in form of small-dimension zinc disc or
wire fixed on and electrically connected with the reinforcement bar. Then missing layer of concrete is applied covering the rebar together with the protector. As long as the concrete layer is not penetrated by water, ions and the front of carbonation is
away from the reinforcement, steel does not corrode and the protectors play a waiting role. The moment the aforementioned
agents reach the rebar the sacri ficial anodes start to provide electrochemical protection. The second variant of protection is ideally suited for the degraded pillars calling for restoration where the reinforcement is revealed and exposed to atmospheric
conditions. In case of both approaches the effectiveness of applied protection as well as the time instant when the protector
has to be replaced can be monitored and determined by measurements of electrochemical potential of the pillar ''s [(Fig._5)TD$IG] Fig. 5. Examples of cracks on the border between original material and new additions after 10 years of exposure. The red arrow indicates the crack and the
blue rectangle the new mortar. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article). A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48 45 [(Fig._6)TD$IG] Fig. 6. Suggested methods of pole protection. Two variants: sacri ficial anode situated in soil (a) and sacrificial anode situated inside concrete cover of the pole (b). 46 A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48 reinforcement. Both proposed variants of electrochemical protection have already been implemented at separate pillars
present on the area of the former Auschwitz camp (Fig. 7a and b). [(Fig._7)TD$IG] Fig. 7. Pillars located in the former Auschwitz camp protected with sacri ficial anodes before applying a new repair mortar: variants with protector buried in soil (a), variant with protector placed directly on reinforcement (b). A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48 47 In order to increase the ef ficiency of protection and lifetime of the pillars equipped with cathodic protection systems it is also proposed to apply hydrophobic treatment to the pillars (Fig. 6). In this way thin film of water repellent agent is going to be deposited on the concrete surface signi ficantly elongating the time of water ingress into vicinity of the reinforcement. 5. Summary and conclusions The case-study presented allows to draw the following conclusions: - A number of reinforced concrete pillars present on the area of former Auschwitz concentration and extermination camp call for restoration due to their signi ficant degradation following 70 years of atmospheric exposure. - The pillars, which were subjected to repair 10 years ago reveal de ficiencies in applied restoration exemplified as cracking between original concrete part of the pillar and the fresh mortar applied during the restoration. - The possible reasons of the interfacial cracking between original and new concrete layers are: shrinkage of mortar upon settlement or more probably corrosion process occurring on the reinforcement causing the concrete to crack. - Two variants of protection of the pillars were proposed: the first one consisted in application of sacrificial anode buried in ground in vicinity of the pillar; the second one predicts placement of protector discs or wires directly on the reinforcement
and covering them with missing concrete layer. - Both variants ful fill the requirements for conservation of historical heritage objects as the applied protection methods do not change the appearance of the pillars perceived by the visitors of the Museum. - Both variants of protection are proposed to be supplemented with hydrophobic treatment of concrete surface to elongate the time necessary for water to reach the reinforcement. Acknowledgment The study was conducted as part of the Master Plan for Preservation at the Auschwitz-Birkenau State Museum. References Ann, K.Y., Pack, S.W., Hwang, J.P., Song, H.W., Kim, S.H., 2010. Service life prediction of a concrete bridge structure subjected to carbonation. Constr. Build. Mater. 24, 1494 ''1501. Auschwitz Report, 2014. Available at: http://auschwitz.org/en/museum/news/, news dated (05.08.15).
Bertolini, Carsana, M., Redaelli, E., 2008. Conservation of historical reinforced concrete structures damaged by carbonation inducted corrosion by means of electrochemical realkalisation. J. Cult. Herit. 9, 376 ''385. Bartolini, L., Elsener, B., Pedeferri, P., Redaelli, E., Polder, R.B., 2013. Corrosion of Steel in Concrete: Prevention, Diagnosis Repair, 2nd edition Wiley-VCh, Weinheim. Crevello, G., Hudson, N., Noyce, P., 2015. Corrosion conditions evaluations of historic concrete icons. Case Stud. Constr. Mater. 2, 2 ''10. Franzoni, E., Varum, H., Natali, M.E., Bignozzi, M.C., Melo, J., Rocha, L., Pereira, E., 2014. Improvement of historic reinforced concrete/mortars by impregnation and electrochemical methods. Cem. Concr. Compos. 49, 50 ''58. Jaffer, J.S., Hansson, C.M., 2009. Chloride-inducted corrosion products of steel in craced-concrete subjected to different loading conditions. Cem. Concr. Res. 39, 116 ''125. Mietz, J., 1995. Electrochemical realkalisation for rehabilitation of reinforced concrete structures. Mater. Corros. 46, 527 ''533. Mosoarca, M., Victor, G., 2013. Structural safety of historical buildings made of reinforced concrete, from Banat region ''Romania. J. Cult. Herit. 14S, e29''e34. Nguyen, T.T.H., Bary, B., De Larrard, T., 2015. Coupled carbonation-rust formation-damage modeling and simulation of steel corrosion in 3D mesoscale reinforced concrete. Cem. Concr. Res. 74, 95 ''107. Pagliolico, S.L., Doglione, R., Tulliani, J.-M., 2014. Diagnosis of the surface layer damage in a 1960 reinforced concrete building. Case Stud. Constr. Mater. 1, 77 ''82. Redaelli, E., Lollini, F., Bertolini, L., 2014. Cathodic protection with localised galvanic anodes in slender carbonated concrete elements. Mater. Struct. 47, 1839 '' 1855. The architecture of crime. In: Swiebodzka, T. (Ed.), The Security and Isolation System of the Auschwitz Camp. Auschwitz-Birkenau State Museum, Oswiecim.
Wilson, K., Jawed, M., Ngala, V., 2013. The selection and use of cathodic protection systems for the repair of reinforced concrete structures. Constr. Build. Mater. 39, 19 ''25. Zheng, H., Li, W., Ma, F., Kong, Q., 2012. The effect of a surface-applied corrosion inhibitor on the durability of concrete. Constr. Build. Mater. 37, 36 ''40. 48 A. Miszczyk et al. / Case Studies in Construction Materials 4 (2016) 42 ''48

Document Outline

Restoration and preservation of the reinforced concrete poles of fence at the former Auschwitz concentration and extermina ... 1 Introduction 2 Mechanism of destruction 3 Used method of restoration and preservation 4 Suggested modification of the used methods 5 Summary and conclusions Acknowledgment References


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