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Role of clays in the deterioration of stone: application in the conservation of the ‘Molasse du Midi’ in terms of durability and compatibility of materials used

Role of clays in the deterioration of stone: application in the conservation of the ‘Molasse du Midi’ in terms of durability and compatibility of materials used

Programme start: 2009

CICRP: Philippe Bromblet (director), Jérémie Berthonneau (doctoral student 2010–2012), Jean-Marc Vallet

Partnership(s): Bureau of Geological and Mining Research (BRGM), Center for Interdisciplinary Nanoscience of Marseille (CINaM) (Aix-Marseille University), PACA Regional Council

This project forms the topic of a thesis (Jérémie Berthonneau) cofinanced by the BRGM, the PACA Regional Council and the CICRP, focusing on the role of clays in the deterioration of stone, and more specifically on the spalling affecting monuments built from Burdigalian molasses in the region. Petrophysical, petrographic and mineralogical profiles as well as hydric and hygric dilation tests have been carried out on the full range of samples taken from approximately 30 quarries and a few monuments. Field visits have been carried out to evaluate the durability of the stones studied in the regional heritage. These investigations have shown that there is a relationship between the clay content, the amplitude of the dilations and the alterability of the molasse. Qualitative and quantitative analyses of clay minerals are in progress using different methodologies (DRX and MET/EDS) on approximately 10 of the more alterable and clay-rich facies to determine precisely the impact of swelling clay materials and their location in the material in the development of spalling.

Publications:

  • J. Berthonneau, ‘Relationships between internal properties and durability in the « Molasse du Midi » limestone (South-East of France)‘, Euromat Colloquium, Montpellier 2011, summary and communication
  • J. Berthonneau, O. Grauby, A. Baronnet, D. Dessandier, P. Bromblet and J.-M. Vallet, ‘Role of swelling clay minerals in the spalling decay mechanism of the « Molasse du Midi » limestone (South-east of France)’, 12th International Congress on the Deterioration and Conservation of Stone, 2012.
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