Analysis and recognition of dolomitic lime mortars (original) (raw)
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Proceedings of the 5th Historic Mortars Conference, 2019
The Benedictine convent of St. John at Müstair (UNESCO world heritage site) in Grisons, Switzerland, preserves a huge amount of well-documented (dolomitic) archaeological mortar samples dated from the Carolingian to the Baroque Age (8 th to 18 th century). In the medieval period, the architecture of the Val Müstair and the surrounding regions was characterized by stone and mortar constructions. The geological overview of the area around the monastery indicates that dolomitic rocks are widely available and the production of lime was a common practice in the Müstair valley as demonstrated by the presence of mortar mixers, lime-kilns and local toponyms. As part of an ongoing research project, the question about the potential source(s) of the raw materials for the production of the binder of the historic mortars was posed. The proposed research is based on the close relationship between the geological raw materials and the underburnt relics (lime lumps) found in the archaeological mortars. Textural features and mineralogical composition were investigated by combining Polarizing Light Microscopy (PLM) and X-ray Powder Diffraction (XRPD) analysis. Results indicate that the textural evidence (sometimes) retained by underburnt relics of dolomitic rocks cannot be used as possible criteria for provenance studies due to the high variability of dolomite crystal size, fabric and heterogeneity within the same group and at the scale of individual samples. However, the presence of silicate phases may suggest potential proxies.
Chemical Analysis of Historic Lime Mortars: Role of Sample Preparation
Advanced Materials Research, 2015
The characterization of historic lime mortars is crucial for many cultural heritage conservation issues. In this work, the characterization of a historical lime mortar is described. Samples for chemical analysis were obtained after different milling times and using the RILEM acid digestion method on several replicates. Qualitative and quantitative determination of phases in the mortar and in the residues after acid attack and the potential presence of CaCO3 polymorphs, were accomplished with X-ray powder diffraction. Results suggest that representativeness of the sample and the homogenisation, although not always achievable in conservation practice, are strongly affecting results.
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...
Essempi di Architettura, 2015
Two types of lime mortar (glue and plaster) have been characterized, and these types of lime mortar were used in the construction of masonry bridges, called Puente Calicanto or Puente Ortiz, which are located in Cali (Colombia) and were put into service in 1845. To this end, the techniques of Xray Diffraction (XRD), Infrared Spectroscopy by Fourier Transform (FT-IR), Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) have been employed. Using these different techniques, it can be concluded that each of these mortars exhibit differences in the proportion of their constituent materials, and the successful use of empirical knowledge can be demonstrated in the selection of the types of lime used by the builders. XRD characterization is adequate when crystalline phases are present, but for low-crystallinity materials, FT-IR analysis and DSC are more appropriate.
The petrography of lime inclusions in historic lime based mortars
Lime inclusions are fine to coarse grained lumps of unmixed binder material commonly found in old mortars in historic buildings. Interpretations for their origin have been advanced including the practice of "hot mixing" or "dry-slaking" of quicklime direct with sand and water and poor mechanical combination of the material prior to application. Their composition and microstructure may provide clues as to their origin and to their preservation. Several historic mortars from Scotland and Belgium have been investigated. This paper presents details of the inclusions found in these mortars. A number of different textures are evident from clotted, peliodal to psuedomorphs of precursor limestones. The presence of cores of unburnt limestone with coronas of hydrated lime texture suggest a possible reason for the integrity of lime inclusions throughout the mixing and application procedures. Lime inclusions also provide material for the assessment of the composition and provenance of the raw materials, and the freshly burnt lime, without the influence of mortar additives such as pozzolans. The presence of lime lumps are useful in suggesting the nature of historic mortar production and application practices.
Microchemical Journal, 2019
This work presents a chemical-mineralogical study of archaeological lime mortars from Amaiur Castle (Navarre, Spain) dated between the 14th and 17th centuries. The study focuses on the analysis of the reaction zone observed around the dolomitic aggregates of lime mortars by means of optical microscopy, scanning electron microscopy with X-ray microanalysis, micro-Raman spectroscopy and X-ray diffraction. Multi-analytical analysis show that the reaction zone is composed of two reaction rims and a halo formed as result of the dedolomitization of dolomitic mortar aggregates in a strongly alkaline medium. The mineralogical results suggest mortars cured at around 60°C, pointing to a traditional hot-mixing manufacture method. 2. Materials and methods 2.1. Samples Archaeological lime mortar samples from Amaiur Castle (Navarre Spain) were analyzed in order to study the reaction zone in dolomitic aggregates. The mortars belong to structures built in different periods: a wall between the 14th and15th centuries, a 16th century bastion and fillings, and a second bastion dated in the 17th century (Fig. 1).
Geochemical Characterization of Archeological lime Mortars: Provenance inputs
"Chemical and mineralogical analyses were carried out on historical lime mortars from the parish church of Santa María La Real (Guipúzcoa). The study included various periods ranging from Roman to modern times and allowed the identification of various types of raw materials. In order to obtain pure binder, free of carbonate aggregates and charcoal particles, an innovative binder separation method was implemented. The chemical composition of the binder allows discrimination of different provenance areas for the raw materials, although those areas do not correlate with specific historical periods. In addition, the influence of burial processes on the primeval chemical features has been assessed and reveals that modern mortars display greater chemical modification than the Roman mortars."
Microstructural Characterization of Mortars
2016
The variability of the internal structure of the coating mortar makes the analysis and comparison of the various performance properties a complex task. To facilitate it, the use of advanced characterization and diagnostic techniques contribute to a better analysis of the chemical, mineralogical and microstructural mortars, and the establishment of the relevant performance parameters. In the scope of thermal mortar properties, various formulations with light weight aggregates (expanded cork, expanded clay and silica aerogel) were used. The methodology of the study includes X-ray Microtomography (micro-CT), Electronic Scanning Microscope (SEM), X-ray Diffraction (DRX) and Infrared Spectroscopy Fourier Transform (FTIR), and Stereo Microscopy. Thus, it is intended to study the solid structure in terms of the aggregate, binder and aggregate/binder interface, and the porous structure regarding to the amount, shape, size and connecting pores. In addition, information was obtained on the co...
Geochemical Characterization of Archaeological Lime Mortars: Provenance Inputs
Archaeometry, 2008
Chemical and mineralogical analyses were carried out on historical lime mortars from the parish church of Santa María La Real (Guipúzcoa). The study included various periods ranging from Roman to modern times and allowed the identification of various types of raw materials. In order to obtain pure binder, free of carbonate aggregates and charcoal particles, an innovative binder separation method was implemented. The chemical composition of the binder allows discrimination of different provenance areas for the raw materials, although those areas do not correlate with specific historical periods. In addition, the influence of burial processes on the primeval chemical features has been assessed and reveals that modern mortars display greater chemical modification than the Roman mortars.