Characterization and compatibility assessment of commercial stone repair mortars

Barbara Lubelli*, Timo G. Nijland, Rob P.J. van Hees

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Compatibility of repair materials in conservation is a widely desired goal, but difficult to achieve. In this research, the compatibility of four commercial stone repair mortars, commonly used in conservation practice in the Netherlands and neighbouring countries, is discussed. In order to do so, they have been characterized in laboratory. The composition of the repair mortars, their content of soluble salts, porosity and pore size distribution, hygric dilation and flexural and compressive strength were measured. The effect of curing was assessed by comparing specimens cured in laboratory and under outdoor conditions. The effect of 3 years outdoor exposure on the curing and weathering of the mortars was evaluated. The results show that the composition of the selected mortars varies significantly, even though, based on their technical information sheets, they appeared to be similar. Consequently, their moisture transport properties differ significantly. As expected, both the type of binder and the porosity were shown to affect the mechanical properties of the mortar: the mortar based on an inorganic polymer binder showed the highest mechanical strength; the most porous, lime- or lime-cement-based mortars, showed the lowest mechanical strength. Based on compatibility criteria defined in literature and the results obtained in this research, an attempt was made to assess the technical compatibility of the selected mortars with building stones commonly used in the Netherlands. It was found that some requirements are hard to be fulfilled and not all requirements can be fulfilled at the same time. Besides, technical sheets of commercial mortars are often incomplete; therefore repair mortars can hardly be selected based only on the properties reported by the producers.

Original languageEnglish
Pages (from-to)174-182
Number of pages9
JournalJournal of Cultural Heritage
Volume49
DOIs
Publication statusPublished - 2021

Keywords

  • Compatibility
  • Microstructure
  • Porosity
  • Stone repair mortars
  • Strength

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