Alteration process of stone by crystallisation of soluble salts
CICRP programme steering: Philippe Bromblet (director) and Jean-Marc Vallet
Partnership(s): Center for Interdisciplinary Nanoscience of Marseille (CINaM), Paul Cézanne Aix University – Marseille III
The research efforts on the role of soluble salts in the alteration of materials have been carried out primarily in the context of the doctorate of Julie Désarnaud, student co-supervised by the CINaM and the CICRP. This doctorate, entitled ‘Alteration process of stones by cristallisation of soluble salts’, has been financed by a PACA regional grant.
This research has consisted in renewing the experiments carried out since 1920 (Taber, Correns etc.) that are at the root of the concept of cristallisation pressure. An experimental device was developed to measure the displacement induced by potential growth of the constrained faces of a KCl crystal submerged in a saturated solution in a controlled environment of T and HR and subjected to a known initial theoretical constraint on its upper face. The dimensions and weights of crystals are monitored before and after the experiment. The development of the height of the crystal is continuously monitored during the entire duration of the experiment by a displacement sensor. The experiment is carried out under different conditions (contact or near-contact of the mechanical constraint and the crystal, different rates of solution saturation etc.). In every case, the height of the crystal decreases progressively through the dissolution of the constrained summital and basal faces. The constrained faces have a higher solubility than the non-constrained faces and dissolve under mechanical constraint in every scenario, in accordance with Riecke’s principle as well as the general laws of crystalline growth. These experiments call into question the notion of crystallisation pressure as referred to in alteration phenomena of stone relating to soluble salts.
- Workshop CRYSPOM 1 organised by the École Nationale des Ponts et Chaussées in Paris in 2008, communication and publication of the summary ‘Crystal growth under mechanical constraint: new experimental results using KCl‘, J. Désarnaud, p. 1.
- Workshop CRYSPOM 2 organised by ETH Zurich in 2010 at Brienz, Switzerland, communication and publication of the summary, ‘Growth and dissolution of a loaded KCl crystal: Impact and limit of the supersaturation rate‘, Desarnaud J., Baronnet A., Bromblet P., Vallet J.-M. and Grauby O., p. 1.
- Désarnaud J., Baronnet A., Bromblet P., Grauby O. and Vallet J.-M. (2008), ‘Crystal growth under mechanical constraint: new experimental results using KCl’, Proceedings from the International Conference on Salt Weathering of Buildings and Stone Sculptures, 22–24/10/2008, Copenhagen, Denmark, Technical University of Denmark, 103–113.
- Désarnaud J., ‘Mécanisme de croissance et de dissolution de cristaux de KCl sous charge, apport dans la connaissance des altérations des pierres par les sels’, thesis of Paul Cézanne Aix University – Marseille III, 2009, p. 197.
- Désarnaud J., Baronnet A., Bromblet P., Grauby O. and Vallet J.-M., ‘Growth and dissolution of crystals under load: new experimental results on KCl‘, submitted to Crystal Growth & Design.