Investigative methods for the characterisation of historic mortars—Part 1: Mineralogical characterisation

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 a combination of methods, including chemical analysis methods. All methods of characterisation require qualified and experienced people to cary out the analyses.RésuméLa caractérisation minéralogique des mortiers historiques est exécutée pour des raisons différentes qui sont liées à la conservation des constructions traditionnelles. Les raisons de l’analyse et les questions posées lors de la conservation, la réparation ou la restauration d’une construction historique déterminent les méthodes d’analyse choisies. Une gamme de méthodes de caractérisation minéralogique est disponible pour l’étude des mortiers historiques de maçonnerie. Celles-ci comprennent la diffractométrie par rayon X (DRX), la microscopie optique, la microscopie électronique de balayage (MEB), les méthodes thermiques et infrarouge. La préparation de l’échantillon est importante: la séparation adéquate du liant et du granulat est obligatoire pour des méthodes instrumentales (comme les analyses chimiques), ce qui n’est pas le cas pour les méthodes d’investigation microscopiques. Il est difficile, et peut-être peu judicieux, d’analyser un mortier avec une seule méthode de caractérisation. Un schéma systématique relatif aux analyses à exécuter peut être développé et est présenté sous forme d’organigramme. Toutes les méthodes de caractérisation exigent du personnel qualifié et expérimenté pour exécuter les analyses.

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