Akademischer Direktor am Geologischen Institut der RWTH Aachen. Leiter der AG Natursteine und Verwitterung Experte für Natursteine,Verwitterung,Schadensdiagnose historischer Bauwerke ,Denkmalschutz.
The destructive impact of biodeterioration processes on the structural substance of historical mo... more The destructive impact of biodeterioration processes on the structural substance of historical monuments, and distinct individual objects of art made of various kinds of materials, means that conservation and restoration practice requires adequate and non-hazardous methods for their sterilisation and preservation. The studies presented here will show how highly microbially contaminated carbonate rocks and different quartzitic sandstones, mainly originating from archaeological diggins of Roman settlements in Trier (Germany), were completely sterilised by ethylene oxide without any measurable changes to the mineralogical structure and physical characteristics. In view of the fact that several biocides have recently been banned, and that ethylene oxide is regarded as highly toxic, this commercial procedure is under the close control of health authorities. However, it seems to be one of the few methods with some future in the decontamination of objects of the cultural heritage. The application of the documented results for a successful anti-microbial treatment of other objects of art is discussed. -- ICCROM
Zeitschrift Der Deutschen Gesellschaft Fur Geowissenschaften, 2005
Weltweit werden große Anstrengungen zur Erhaltung verwitterungsgeschädigter Natursteinbauwerke un... more Weltweit werden große Anstrengungen zur Erhaltung verwitterungsgeschädigter Natursteinbauwerke unternommen. Einhellig vertreten heute alle Bausachverständigen die Meinung, dass der Weg vom geschädigten zum dauerhaft und kostengünstig sanierten Bauwerk nur über eine gesicherte Material-und Schadensdiagnose führt. Die Bauwerkskartierung ist ein zerstörungsfreies, zeit-und kostengünstiges Diagnoseverfahren, das vielfältige Dokumentationsmöglichkeiten und eine quantitative Bewertung der Verwitterungsschäden an Natursteinbauwerken erlaubt. Sie empfiehlt sich für den routinemäßigen Einsatz in der Denkmalpflege. Methode und Anwendungsbeispiele der Bauwerkskartierung werden vorgestellt.
Many Maltese monuments made from Globigerina limestones today show damages of alarming intensity.... more Many Maltese monuments made from Globigerina limestones today show damages of alarming intensity. Salt weathering can be recognized as an important process evoking the stone deterioration. At representative monuments the occuring damages were registered and documented. Laboratory analyses were executed for the determination of characteristical stone properties. Correlations between stone properties and weathering behaviour were deducted and, furthermore, statements with regard to monument preservation works.
Macla: revista de la Sociedad Española de Mineralogía, 2014
Stone monuments represent an important part of our world´s cultural heritage. The awareness of in... more Stone monuments represent an important part of our world´s cultural heritage. The awareness of increasing stone damage on monuments and the danger of further irretrievable loss of cultural heritage have resulted in great efforts worldwide for sustainable monument preservation. A precise damage diagnosis with comprehensive characterization, interpretation and rating of stone damage represents the basis for effective and economic monument preservation measures. The experienced methodological approach to the assessment of stone damage combines in situ investigation and laboratory studies. The monument mapping method is presented as an established non-destructive procedure for in situ studies on stone damage. It can be applied to all stone types and to all kinds of stone monuments. The use of weathering forms, damage categories and damage indices for the registration, documentation, quantitative evaluation and rating of stone damage is explained. Furthermore, complementary in situ measurements are discussed.
Summary Weathering damage of varying intensity occurs at the monuments in the ancient town of Pet... more Summary Weathering damage of varying intensity occurs at the monuments in the ancient town of Petra. These monuments are carved out of bedrock. As a result of fieldwork, the rocks were differentiated according to lithology. Furthermore, the weathering forms at the monuments were classified and mapped. From these results models of the development of weathering forms could be constructed. Additionally, microclimatic data were registered. Petrographie characteristic values relevant to weathering were determined through laboratory experiments on rock samples.
... 4. Profile measurements with a commercial profile comb were made at 30 petroglyphs of the Bro... more ... 4. Profile measurements with a commercial profile comb were made at 30 petroglyphs of the Bronze Age for ... A cor-relation scheme ''weathering forms, damage categories'' was developed for the monument under investigation, in which all ... Very fine sand (63125 μm) 14.3 17.6 ...
Calcarenite from Puerto de Santa Maria, a stone widely used in historic monuments of Western Anda... more Calcarenite from Puerto de Santa Maria, a stone widely used in historic monuments of Western Andalucia, does not show important porosity variations after five hundred years of weathering in the Cartuja of Seville. However, its macroporosity (o 10-300µ) falls from 14% to 10% after a treatment with Tegovakon, an ethyl silicate harder, because of amorphus silica is deposited into the big pores, and also to surface area of micropores encreases due to the silica gel presence, but the porosity of the stone treatted with Tegosivin, a water repellent, does not vary. Nevertheless, both treatments lead to an abruptly decreasing of water absorption. In order to improve the technical characteristics of the Puerto stone as building material, a previous protection treatment with a harder followed of a water repellent is suggested.
The consolidation of weathered tuff material is problematical in most cases due to their unusual ... more The consolidation of weathered tuff material is problematical in most cases due to their unusual pore size distribution. For the case of the Rano Raraku tuff of Easter Island under study, the distribution shows a trimodal pattern. The problem arises because the smallest capillary pores are not reached by the liquid, gel-forming consolidants, such as silicate esters, which mainly fills the larger capillary pores. Thus, the weakened area around the smallest capillary pores is not reinforced. Furthermore, the enormous rates of hygric swelling observed for this material contribute to curtail the durability of this type of consolidation treatment. This study tested commercially available and modified silicate esters, as well as newly developed anti-swelling agents on Rano Raraku tuff samples taken from the quarry and from broken moai (statues). Treated and untreated specimens were studied by SEM and their pore size distribution and specific surfaces determined. Their hygroscopicity, hygric dilation and their drill resistance were also measured. Both treated and untreated specimens were then subjected to artificial weathering, simulating an exaggerated Easter Island subtropical climate, and the studies and aforementioned measurements repeated. The results obtained are discussed and the possible durability of the treatments assessed.
The Pharaonic stone monuments in Upper Egypt represent cultural heritage of outstanding universal... more The Pharaonic stone monuments in Upper Egypt represent cultural heritage of outstanding universal value. All monuments have suffered weathering damage. In the year 2000 an Egyptian-German research cooperation was started aiming at the systematic investigation of stone weathering on the historical monuments in Upper Egypt as a contribution to monument preservation. Pilot studies were carried out on the Karnak Temple and on the Luxor Temple, composed of sandstones originating from the Gebel el-Silsila region. First results on the petrographical properties of these sandstones and their state of weathering damage on the Pharaonic temples in Luxor are presented.
Stone monuments represent an important part of our world´s cultural heritage. The awareness of in... more Stone monuments represent an important part of our world´s cultural heritage. The awareness of increasing stone damage on monuments and the danger of irretrievable loss of cultural heritage have resulted in great efforts worldwide for sustainable monument preservation. A precise damage diagnosis with the comprehensive characterization, interpretation and rating of stone damage represents the basis for effective and economic monument preservation measures. The experienced methodological approach to the assessment of stone damage combines in situ investigation and laboratory studies. The monument mapping method is presented as an established nondestructive procedure for in situ studies on stone damage. It can be applied to all stone types and to all kinds of stone monuments. The use of weathering forms, damage categories and damage indices for the registration, documentation, quantitative evaluation and rating of stone damage is explained. Furthermore, complementary in situ measurements are discussed. A wide range of analytical procedures and weathering simulation tests contribute to modern damage diagnosis on stone monuments.
The destructive impact of biodeterioration processes on the structural substance of historical mo... more The destructive impact of biodeterioration processes on the structural substance of historical monuments, and distinct individual objects of art made of various kinds of materials, means that conservation and restoration practice requires adequate and non-hazardous methods for their sterilisation and preservation. The studies presented here will show how highly microbially contaminated carbonate rocks and different quartzitic sandstones, mainly originating from archaeological diggins of Roman settlements in Trier (Germany), were completely sterilised by ethylene oxide without any measurable changes to the mineralogical structure and physical characteristics. In view of the fact that several biocides have recently been banned, and that ethylene oxide is regarded as highly toxic, this commercial procedure is under the close control of health authorities. However, it seems to be one of the few methods with some future in the decontamination of objects of the cultural heritage. The application of the documented results for a successful anti-microbial treatment of other objects of art is discussed. -- ICCROM
Zeitschrift Der Deutschen Gesellschaft Fur Geowissenschaften, 2005
Weltweit werden große Anstrengungen zur Erhaltung verwitterungsgeschädigter Natursteinbauwerke un... more Weltweit werden große Anstrengungen zur Erhaltung verwitterungsgeschädigter Natursteinbauwerke unternommen. Einhellig vertreten heute alle Bausachverständigen die Meinung, dass der Weg vom geschädigten zum dauerhaft und kostengünstig sanierten Bauwerk nur über eine gesicherte Material-und Schadensdiagnose führt. Die Bauwerkskartierung ist ein zerstörungsfreies, zeit-und kostengünstiges Diagnoseverfahren, das vielfältige Dokumentationsmöglichkeiten und eine quantitative Bewertung der Verwitterungsschäden an Natursteinbauwerken erlaubt. Sie empfiehlt sich für den routinemäßigen Einsatz in der Denkmalpflege. Methode und Anwendungsbeispiele der Bauwerkskartierung werden vorgestellt.
Many Maltese monuments made from Globigerina limestones today show damages of alarming intensity.... more Many Maltese monuments made from Globigerina limestones today show damages of alarming intensity. Salt weathering can be recognized as an important process evoking the stone deterioration. At representative monuments the occuring damages were registered and documented. Laboratory analyses were executed for the determination of characteristical stone properties. Correlations between stone properties and weathering behaviour were deducted and, furthermore, statements with regard to monument preservation works.
Macla: revista de la Sociedad Española de Mineralogía, 2014
Stone monuments represent an important part of our world´s cultural heritage. The awareness of in... more Stone monuments represent an important part of our world´s cultural heritage. The awareness of increasing stone damage on monuments and the danger of further irretrievable loss of cultural heritage have resulted in great efforts worldwide for sustainable monument preservation. A precise damage diagnosis with comprehensive characterization, interpretation and rating of stone damage represents the basis for effective and economic monument preservation measures. The experienced methodological approach to the assessment of stone damage combines in situ investigation and laboratory studies. The monument mapping method is presented as an established non-destructive procedure for in situ studies on stone damage. It can be applied to all stone types and to all kinds of stone monuments. The use of weathering forms, damage categories and damage indices for the registration, documentation, quantitative evaluation and rating of stone damage is explained. Furthermore, complementary in situ measurements are discussed.
Summary Weathering damage of varying intensity occurs at the monuments in the ancient town of Pet... more Summary Weathering damage of varying intensity occurs at the monuments in the ancient town of Petra. These monuments are carved out of bedrock. As a result of fieldwork, the rocks were differentiated according to lithology. Furthermore, the weathering forms at the monuments were classified and mapped. From these results models of the development of weathering forms could be constructed. Additionally, microclimatic data were registered. Petrographie characteristic values relevant to weathering were determined through laboratory experiments on rock samples.
... 4. Profile measurements with a commercial profile comb were made at 30 petroglyphs of the Bro... more ... 4. Profile measurements with a commercial profile comb were made at 30 petroglyphs of the Bronze Age for ... A cor-relation scheme ''weathering forms, damage categories'' was developed for the monument under investigation, in which all ... Very fine sand (63125 μm) 14.3 17.6 ...
Calcarenite from Puerto de Santa Maria, a stone widely used in historic monuments of Western Anda... more Calcarenite from Puerto de Santa Maria, a stone widely used in historic monuments of Western Andalucia, does not show important porosity variations after five hundred years of weathering in the Cartuja of Seville. However, its macroporosity (o 10-300µ) falls from 14% to 10% after a treatment with Tegovakon, an ethyl silicate harder, because of amorphus silica is deposited into the big pores, and also to surface area of micropores encreases due to the silica gel presence, but the porosity of the stone treatted with Tegosivin, a water repellent, does not vary. Nevertheless, both treatments lead to an abruptly decreasing of water absorption. In order to improve the technical characteristics of the Puerto stone as building material, a previous protection treatment with a harder followed of a water repellent is suggested.
The consolidation of weathered tuff material is problematical in most cases due to their unusual ... more The consolidation of weathered tuff material is problematical in most cases due to their unusual pore size distribution. For the case of the Rano Raraku tuff of Easter Island under study, the distribution shows a trimodal pattern. The problem arises because the smallest capillary pores are not reached by the liquid, gel-forming consolidants, such as silicate esters, which mainly fills the larger capillary pores. Thus, the weakened area around the smallest capillary pores is not reinforced. Furthermore, the enormous rates of hygric swelling observed for this material contribute to curtail the durability of this type of consolidation treatment. This study tested commercially available and modified silicate esters, as well as newly developed anti-swelling agents on Rano Raraku tuff samples taken from the quarry and from broken moai (statues). Treated and untreated specimens were studied by SEM and their pore size distribution and specific surfaces determined. Their hygroscopicity, hygric dilation and their drill resistance were also measured. Both treated and untreated specimens were then subjected to artificial weathering, simulating an exaggerated Easter Island subtropical climate, and the studies and aforementioned measurements repeated. The results obtained are discussed and the possible durability of the treatments assessed.
The Pharaonic stone monuments in Upper Egypt represent cultural heritage of outstanding universal... more The Pharaonic stone monuments in Upper Egypt represent cultural heritage of outstanding universal value. All monuments have suffered weathering damage. In the year 2000 an Egyptian-German research cooperation was started aiming at the systematic investigation of stone weathering on the historical monuments in Upper Egypt as a contribution to monument preservation. Pilot studies were carried out on the Karnak Temple and on the Luxor Temple, composed of sandstones originating from the Gebel el-Silsila region. First results on the petrographical properties of these sandstones and their state of weathering damage on the Pharaonic temples in Luxor are presented.
Stone monuments represent an important part of our world´s cultural heritage. The awareness of in... more Stone monuments represent an important part of our world´s cultural heritage. The awareness of increasing stone damage on monuments and the danger of irretrievable loss of cultural heritage have resulted in great efforts worldwide for sustainable monument preservation. A precise damage diagnosis with the comprehensive characterization, interpretation and rating of stone damage represents the basis for effective and economic monument preservation measures. The experienced methodological approach to the assessment of stone damage combines in situ investigation and laboratory studies. The monument mapping method is presented as an established nondestructive procedure for in situ studies on stone damage. It can be applied to all stone types and to all kinds of stone monuments. The use of weathering forms, damage categories and damage indices for the registration, documentation, quantitative evaluation and rating of stone damage is explained. Furthermore, complementary in situ measurements are discussed. A wide range of analytical procedures and weathering simulation tests contribute to modern damage diagnosis on stone monuments.
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