Petrography of historic mortar materials: polarising light microscopy as a method for characterising lime-based mortars

Kristin Balksten, Bo Nitz, John J. Hughes, Jan-Erik Lindqvist

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In studying historic, repair and restoration mortars comprised of lime-based material there is an analytical method that answers more questions than any other; transmitted (and reflected) polarised light microscopy (PLM). The present study is based on thin-section analysis of historic and restoration mortars made by the authors in Sweden and Scotland since the 1980’s, previous research [1, 2, 3, 4] and petrographic atlases [5, 6, 7, 8]. This paper is written to be a pedagogically useful complement to previous work.

We present a selection of microphotographs to show the variety of questions that the method can give answers to, such as, in the study of:
-lime binder; source materials, hydraulicity, slaking methods, lime lumps, cracking characteristics
-aggregates; grading, mineralogy/lithology and texture
-additives; inorganic puzzolanic materials and organic materials
-paint layers; different binders, pigments, thicknesses
-pore structure; durability, vapour transport and capillarity
-craftsmanship; various application and working techniques

The aim of this paper is to contribute with more illustrations of reference materials and to illustrate the usefulness of Polarising Light Microscopy as a method for characterising lime-based mortars and to review the most significant analyses parameters.
Original languageEnglish
Title of host publicationProceedings of the 5th Historic Mortars Conference
Subtitle of host publicationRILEM Proceedings PRO 130
EditorsJose Ignacio Alvarez, Jose Maria Fernandez, Inigo Navarro , Adrian Duran, Rafael Sirera
Place of PublicationParis
PublisherRILEM Publications S.A.R.L.
Number of pages15
VolumePRO 130
ISBN (Electronic)9782351582220
ISBN (Print)9782351582213
Publication statusPublished - 16 Jul 2019
Event5th Historic Mortars Conference 2019 - Universidad de Navarra, Pamplona, Spain
Duration: 19 Jun 201921 Jun 2019
Conference number: 5

Publication series

NameRILEM Proceedings
PublisherRILEM Publications S.A.R.L.


Conference5th Historic Mortars Conference 2019
Abbreviated titleHMC 2019
Internet address


  • Historic Mortar
  • petrography


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