Understanding historic mortars and their variations : a condition for performing restoration with traditional materials (original) (raw)
Related papers
In order to design a restoration mortar with properties and composition similar to the original mortar, it is important to analyze the historic mortar in several ways. A combination of analyses give information about the mixing ratio between binder and aggregates, chemical composition of the mortar, additives, tool marks, application technique etc. This paper shows the variations in Swedish medieval lime mortars with a high rate of binder. By analysing historic mortar with a combination of ocular investigations, microscopically studies of thin section specimens, Scanning Electron Microscopy and X-Ray Powder Diffraction, all the information needed for designing a restoration mortar, with composition and properties similar to the historic mortar, is gained.
In order to design a restoration mortar with properties and composition similar to the original mortar, it is important to analyze the historic mortar in several ways. A combination of analyses give information about the mixing ratio between binder and aggregates, chemical composition of the mortar, additives, tool marks, application technique etc. This paper shows the variations in Swedish medieval lime mortars with a high rate of binder. By analysing historic mortar with a combination of ocular investigations, microscopically studies of thin section specimens, Scanning Electron Microscopy and X-Ray Powder Diffraction, all the information needed for designing a restoration mortar, with composition and properties similar to the historic mortar, is gained.
A method to recreate historic mortars applied at Norrlanda church on the Island of Gotland, Sweden
In the process of restoring a lime plaster on an old building, a lot of knowledge is needed in order to make the new plaster similar to and compatible with the old one. This work was carried out with the aim to create a method which makes it possible to recreate historic mortars. There are two important steps in the method: i) a practical data base consisting of mortars made with the application of local materials, known craftsmanship and the variation of a number of parameters was produced; ii) a combination of field studies and material analysis methods was used to investigate the structure and properties of the historic mortar. By combining field studies with microscopic studies of mortars in SEM and thin section specimens it was found to be possible to compare historic lime plaster surfaces and new reference surfaces of lime plaster on both a macroscopic and a microscopic scale. Microscopic studies using SEM give information about the type of slaked lime used in the mortar, as well in the reference as in the old mortars. Investigations of thin section specimens in an optical microscope give information about the type of lime and sand used, the mixing ratio, the working technique, the resulting pore structure of the mortar etc. In field studies old plaster surfaces and newly made reference surfaces are compared. It gives knowledge about how the mortars were built up and worked on, which tools that might have been used, how it was lime washed etc. The combination of those studies makes it possible to create restoration mortars with lime slaked as the historic lime, sand with similar particle size distribution curve and mineral composition, similar mixing ratio and pore structure. It is also possible to build up the new plaster in the same way as originally concerning layers and working technique, with similar tools and lime wash with recipes similar to historic ones. The use of the method is illustrated in a case study of the plaster restoration on the medieval church Norrlanda on Gotland, carried out in the summer of 2006.
Research project on ancient and contemporary lime mortars in the walloon region (Belgium)
These studies should improve our restoration habits, which could be usefully re-oriented in order to improve practices on the restoration sites and ensure the permanence of our monuments. The main aim is to understand better the short-, medium-, and long-term behaviour of lime mortars. Some 100 formulations have been developed for laboratory testing according to various standards. A dozen "basic recipes" that should enable us to determine the main differences in their mechanical behaviour according to their composition were subjected to the standardised tests first. Taking these formulae as our starting points, it should be possible to develop other formulae that are better suited for ancient buildings. Our analyse is using a new leading-edge technology, the scratching test, developed at Polytechnic Faculty of Mons (Faculté Polytechnique de Mons). At the same time, mortar samples from buildings and vestiges of all periods from all over the Walloon Region are being collecte...
In the process of restoring a lime plaster on an old building, a lot of knowledge is needed in order to make the new plaster similar to and compatible with the old one. This work was carried out with the aim to create a method which makes it possible to recreate historic mortars. There are two important steps in the method: i) a practical data base consisting of mortars made with the application of local materials, known craftsmanship and the variation of a number of parameters was produced; ii) a combination of field studies and material analysis methods was used to investigate the structure and properties of the historic mortar. By combining field studies with microscopic studies of mortars in SEM and thin section specimens it was found to be possible to compare historic lime plaster surfaces and new reference surfaces of lime plaster on both a macroscopic and a microscopic scale. Microscopic studies using SEM give information about the type of slaked lime used in the mortar, as well in the reference as in the old mortars. Investigations of thin section specimens in an optical microscope give information about the type of lime and sand used, the mixing ratio, the working technique, the resulting pore structure of the mortar etc. In field studies old plaster surfaces and newly made reference surfaces are compared. It gives knowledge about how the mortars were built up and worked on, which tools that might have been used, how it was lime washed etc. The combination of those studies makes it possible to create restoration mortars with lime slaked as the historic lime, sand with similar particle size distribution curve and mineral composition, similar mixing ratio and pore structure. It is also possible to build up the new plaster in the same way as originally concerning layers and working technique, with similar tools and lime wash with recipes similar to historic ones. The use of the method is illustrated in a case study of the plaster restoration on the medieval church Norrlanda on Gotland, carried out in the summer of 2006.
2005
The mineralogical characterisation of historic mortars is performed for a number of reasons related to the conservation of traditional structures. The reasons for analysis and the questions posed during the conservation, repair or restoration of an old building determine the analysis methods that will be chosen. A range of mineralogical characterisation methods is available for the study of historic masonry mortars. These include X-ray Diffraction (XRD), Optical Microscopy, Scanning Electron Microscopy (SEM), Thermal and Infra-Red methods. Sample preparation is important; adequate separation of binder from aggregate is required for instrumental as opposed to microscopic investigation methods. An ordered scheme of analysis can be developed and is presented in flowchart form. It is difficult, and perhaps unwise, to analyse a mortar with only one method of characterisation. Corroboration of evidence of identification and quantification for mineralogical composition is best supported by...
Mortars For Intervention In Monuments And Historical Buildings
WIT Transactions on the Built Environment, 2003
The main problem in designing repair mortars for monuments and historical buildings is their compatibility with the old ones. Many parameters such as colour, texture, porosity, composition, size and type of aggregates as well as mechanical characteristics influence this compatibility. In the framework of many research projects sponsored by the Greek Ministry of Culture and European Committee, a great number of ancient mortars (from monuments of different historical periods) have been analyzed at the Laboratory of Building Materials of Aristotle University of Thessaloniki. Their composition, the physicochemical properties as well as their behaviour were found and studied systematically. Therefore, much experience has been accumulated. Based on this experience a long-term experimental study has been performed concerning the design and the quality of the repair mortars. In this paper the characteristics of a series of lime-based mortar compositions are presented. The research is focuse...
Chemical-mineralogical and physical-mechanical investigations of old mortars
1999
Problems with the fabric of many historic buildings involves damage to mortars, or damage related to interactions with mortars. Characterisation of the chemical and physical attributes of mortar (and allied materials such as render and grout) is often required in order to identify and remedy the causes of decay, or to specify compatible replacement materials. However, within the practical business of analysing the causes of damage, the relationships between sampling, analysis and cost are not always clear. In an effort to clarify this situation and to provide some advice on the options for investigation, the RILEM Technical Committee; "Characterisation of old mortars with respect to their repair" has as an aim: the determination of methods of analysis to be used on mortars to obtain information about their chemical-mineralogical composition and their physical and mechanical properties (1-9).