Analysis of Lime Capping Mortars After Two Decades of Carbonating in Ambient Conditions or Exposed to Natural Weathering at Corfe Castle

Research output: Chapter or section in a book/report/conference proceedingChapter or section

Abstract

In 1993, 13 lime-based mortar mixes were produced for trials at Corfe Castle, Dorset, UK [1, 2]. The trials aimed to evaluate mortars used for consolidating a section of the wall head at Corfe Castle. These mortars had to be resilient to weathering at the exposed location of the castle but remain sacrificial to the underlying historic stone. A sample of each binder and each mortar mix was also placed in sealed polythene bags and stored indoors under ambient conditions (unweathered). In 2019 (weathered) samples of each mortar mix were extracted from the mortar surface and 50 mm below the surface. This paper compares the unweathered and weathered samples for five mortar mixes that used Blue Lias lime putties with different hydraulicities, Unilit B Fluid X (Unilit) hydraulic lime, or Unilit and Chards non-hydraulic lime putty blends. Physical and chemical characterisation was conducted using thermogravimetric analysis (TGA), powder X-ray diffraction, optical imaging, and scanning electron microscopy (SEM) imaging with energy dispersive X-ray (EDX) analysis. These tests enabled a comparison between the hydraulicity and chemical composition of these mixes. TGA results demonstrated that binder choice and weathering conditions had no noticeable impact on carbonation after 26 years. Optical microscopy showed lichen growth on the weathered surface samples but not on the unweathered samples. SEM and EDX identified self-healing of cracks in weathered samples only. Moisture transfer, the ability to self-heal and acting as a barrier between lichen and stone are key features that enabled the mortars to protect the historic material.

Original languageEnglish
Title of host publicationStructural Analysis of Historical Constructions (SAHC 2023)
EditorsY. Endo, T. Hanazato
Place of PublicationCham, Switzerland
PublisherSpringer Science and Business Media B.V.
Pages496-513
Number of pages18
ISBN (Electronic)9783031396038
ISBN (Print)9783031396021
DOIs
Publication statusPublished - 4 Sept 2023

Publication series

NameRILEM Bookseries
Volume47
ISSN (Print)2211-0844
ISSN (Electronic)2211-0852

Bibliographical note

Funding Information:
The authors thank Tugce Bursa Su (University of Bath) for extracting samples from Corfe Castle and Pam White, Abby Horsman, and Martin Taylor (National Trust) for their assistance. Thank you also to Dr Olivier Camus, Diana Lednitzky, Silvia Martínez Micol, Dr Gabriele Kociok-Köhn and Mathew Ball (University of Bath) for technical support [30]. This study was supported by the EPSRC Centre for Decarbonisation of the Built Environment (dCarb) [grant number EP/L016869/1].

Funding Information:
Acknowledgements. The authors thank Tugce Bursa Su (University of Bath) for extracting samples from Corfe Castle and Pam White, Abby Horsman, and Martin Taylor (National Trust) for their assistance. Thank you also to Dr Olivier Camus, Diana Lednitzky, Silvia Martínez Micol, Dr Gabriele Kociok-Köhn and Mathew Ball (University of Bath) for technical support [30]. This study was supported by the EPSRC Centre for Decarbonisation of the Built Environment (dCarb) [grant number EP/L016869/1].

Keywords

  • Crack healing
  • Energy dispersive X-ray analysis
  • Heritage conservation
  • Lime mortar
  • Thermogravimetric analysis
  • Weathering

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Mechanics of Materials

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