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Analytical building material microscopy was established as a research group at the MPA in 1989 and has taken on the task of investigating damage processes on a wide range of building materials relevant to historic monuments. The list of the monument objects examined so far as well as the completed research projects and those currently in progress give a good impression of the great experience that MPA Bremen has gained in this field of research.

The experience gained in the research projects is used by clients from the field of those responsible for the preservation of monuments and historic buildings or the restoration of ageing building materials. The main focus is on damage analysis with petrographic determinations and phase and microstructure descriptions, but also expert opinions regarding a sensible restoration.

A further focus is the microscopic assessment of damage with expert opinions in modern building materials technology. Thereby chemical, physical and biological influences on building and materials are examined and visualized. In particular, the possibilities of electron microscopic investigations using cryo-technology prove to be extremely helpful, e.g. in the assessment of setting and solidification processes in concrete. Currently, intensive cooperation in this field is underway with renowned building material institutes and companies.

Today, microscopic research is also of great importance in the field of building material recycling, where the close cooperation with the research association "Recycling of valuable materials in building material technology", which is located at the MPA, has proved to be particularly beneficial. At present several projects are in progress.

As a special service, asbestos investigations with identification determinations, ambient air measurements and remediation recommendations are offered.

 

Fields of activity at a glance

  • Analysis of damage mechanisms during building material weathering/corrosion (research on monument preservation)
  • Investigation and visualisation of chemical, physical and biological influences on building materials
  • Phase and microstructure analysis / petrography / concreteography
  • Loss clarification and expert opinion
  • Asbestos tests

Projects

Handling of old hydrophobic coatings: Model conservation of objects made of Baumberger sand-lime bricks damaged by old hydrophobization and development of a practice-oriented guideline fiber

In the 50-80s, hydrophobing was carried out in Westphalia on sculptures and ashlars made of the regionally typical Baumberg sand-lime brick almost everywhere.  This often led to consequential damage and further mostly unsuccessful restorations. At the present time, no reliable statement can be made about a sustainable measure for the preservation of these monuments. The main focus of the project is to clarify the material science relationships and to develop a novel modular guide and its dissemination concept for the conservation of the affected objects.

The aim of hydrophobic coatings is to reduce the damage caused by water penetrating the porous natural stone as a result of sprinkling and splashing. Unfortunately, the fact that the objective pursued was usually not achieved can be seen today in many severely damaged natural stone objects. Massive substantial damage due to softening, flaking and peeling can be seen, which is accompanied by a progressive loss of material. The situation in Westphalia is seen as particularly problematic at the monuments made of Baumberger limestone, which are threatened by progressive decay. In the past, unsuccessful attempts were made to counteract a supposedly insufficient resistance to weathering, which was attributed to the specific rock properties (modal composition, bond ratios, porosity, etc.), with a water-repellent impregnation.
Damage detection - MODULE DETECTION
Within the scope of the project, typical damage phenomena on Baumberger sand-lime bricks will be recorded at selected objects in Westphalia. Restorative, scientific and material-technical investigations and developments are carried out on the structures and in the laboratory to record the damage, with special consideration of any old hydrobobing that may have occurred. The material characteristics of the samples from the objects will be compared with those of freshly quarried Baumberg sand-lime bricks from operating quarries in the region. The results will be used to clarify the damage processes. In addition, a survey and evaluation of previous conservation and restoration measures on monuments made of Baumberg sand-lime brick damaged by old hydrophobing will be carried out. Within the scope of this damage detection, it is planned to develop an investigation program for damage definition and condition analysis for a guideline.
Process development - MODULE ACTION
In a second step, materials and methods for the conservation and restoration of objects made of Baumberger sand-lime brick damaged by old hydrophobing are to be designed and developed. In this context, methodical and material-technical interlocking conservation and restoration measures are to be developed in the sense of a modular system (such as cleaning, consolidation, bonding, cavity filling, application, slurry application, etc.). The development of materials and methods for conservation and restoration measures is carried out in a preliminary application and determination of material characteristics. This is done on the basis of individual and composite samples in the laboratory before the developed measures are carried out as sample restorations on selected objects in Westphalia and Lower Saxony.
Maintenance and monitoring - MODULE MAINTENANCE
In the third step of the project, a specific monitoring program will be developed on the basis of the selected and examined objects in Westphalia. This will also be used for further evaluation of the measure on the sample areas.

Sponsor: German Federal Environmental Foundation (DBU)
Processing: IWT-WT-MPA-Civil Engineering
Cooperation partnerships:
Westfälisches Denkmalamt – Denkmalpflege, Landschafts- und Baukultur in Westfalen des Landschaftsverbands Westfalen-Lippe (LWL-DLBW) – Antragsteller
Fachhochschule Potsdam, Studiengang Konservierung/Restaurierung  
Technische Hochschule Köln, Fakultät der Kulturwissenschaften, Studienrichtung Restaurierung und Konservierung
Hochschule für angewandte Wissenschaft und Kunst Hildesheim/Holzminden/Göttingen, Fakultät Bauen und Erhalten, Studienrichtung Konservierung und Restaurierung
Niedersächsisches Landesamt für Denkmalpflege

Contact:
Dr. rer. nat. Frank Schlütter
Telefon: +49421 53708 43
E-Mail: schluettermpa-bremende

 

 

Model development of monitoring and evaluation procedures of mural paintings damaged by anthropogenic environmental influences examined and restored more than 25 years ago

The subject of the project are six exemplarily selected monuments with historical wall paintings, on which extensive investigations with subsequent conservation were carried out from the year 1988 within the framework of the large BMFT project "Research for the Protection of Monuments". In the following decades, these paintings were practically not subjected to any follow-up inspection, so that it is not known whether the recommendations for action at that time led to the hoped-for goal. Modern analytical methods are to be selected and used for a substance-preserving success control based on the current state of knowledge and technology.

In the course of the BMFT's funding programs at that time, a large number of wall paintings could be examined by an interdisciplinary research team, which included both experienced restorers and natural scientists active in the field from the areas of building physics, building material microscopy, chemistry, mineralogy and microbiology, as well as art historians.
The damage identified at the time can be summarized as follows:

  • Direct moisture damage of various origins (rising damp, unregulated water flows and water ingress through damaged areas in the building envelope, condensation caused by cold bridges and climate change)
  • Salt damage (periodic crystallization and re-dissolution under and on the painting surface during climatic changes and associated damage, salt efflorescence) including salts harmful to the building from unsuitable restoration materials or environmental stresses.
  • Mineral strengthening materials (e.g., potassium silicate) that introduce a salt load into the painting layer and support.
  • Organic strengthening materials (natural as well as synthetic materials), which tend to tension in the course of the climate and also lead to detachment of the painting layer, among other things, but also have a substrate effect for microorganisms.
  • Microbiological colonization (mold, bacteria, algae)

Extensive examination results are available from all objects, which are still available in the archives of the coordinating offices at the time and/or the research institutes and laboratories involved. However, a complete compilation or even a comprehensive overview of the results is not available.
For the investigated objects with quite different damage patterns, the results led to concrete recommendations for action, e.g. room air conditioning, salt reduction, structural strengthening.
It is not known in all cases whether and when these recommendations were implemented in the restoration process and whether they led to the desired result. Some of those coordinating and responsible for restoration at the time, as well as the research institutes involved, are still available today, so that an evaluation and examination of these objects after 25-30 years will provide insights into further handling.
The reappraisal will focus on the following questions:

  • What investigations were conducted at the time and what were the results?
  • What recommendations for action and conservation concepts were proposed at the time?
  • Which measures were implemented?
  • Did the proposed concepts lead to success?

Such reflections can evaluate the research projects and results at the time and provide important insights into the sustainability of the proposed conservation concepts. In some cases, it is also possible to obtain complementary or extended results using new research methods that have since been established and were not available at the time.
For example, with the thermodynamic equilibrium states of salt mixtures (instead of the individual salts), which are known in the meantime, recalculations of the equilibrium humidities can be made today and compared with the current room climatic conditions. In this way, any changes in the conditions of use that may have occurred in the meantime, and thus also the heating concepts, can be evaluated both from the point of view of the system and with regard to the climatic parameters defined for control purposes. The same applies to the effects of insulation measures and the replacement of windows and doors.  Significant influences on certain damage processes are to be expected from this. The effects of partial structural repairs to the exterior masonry and foundations can also be assessed.
For the diagnosis of microbial colonization, activity measurements of the energy content of the colonization but also of the photosynthetic activity of algae and cyanobacteria coverings as well as daylight and UV images of the spread of mold infestation in particular, which are to be quantified as far as possible with digital image processing, are suitable. Supplementary laboratory investigations on microbial activity under the climatic conditions prevailing/to be realized in the respective objects are to be carried out on selected isolates.
All investigations in the objects are to be standardized as far as possible and elaborated in such a way that appropriately trained restorers can also carry out the monitoring.

Sponsor: German Federal Environmental Foundation (DBU)
Processing: IWT-WT-MPA-Civil Engineering
Cooperation partner:
Hochschule für angewandte Wissenschaft und Kunst Hildesheim/Holzminden/Göttingen, Fakultät Bauen und Erhalten, Studienrichtung Konservierung und Restaurierung – Antragsteller
Universität Hamburg, Institut für Anorganische und Analytische Chemie
Ingenieurbüro Dr. Helmut Berling, Braunschweig

Contact:
Dr. rer. nat. Frank Schlütter
Telefon: +49421 53708 43
E-Mail: schluettermpa-bremende