Salt weathering

Frans J.P.M. Kwaad,
physical geographer


This website is about the mechanism of salt weathering.

Salt weathering is a form of mechanical or physical weathering of rock. No chemical alteration of rock constituents is involved in salt weathering. The salt derives from an external source (capillary rising ground water, eolian origin, sea water along rocky coasts, atmospheric pollution). Salt weathering is favoured by dry conditions, such as are found in warm and cold (arctic) arid climates. Salt weathering (salt damage, salt decay) also occurs on buildings and monuments in arid climates as well as under dry microclimatic conditions in humid climates. Corrosion by sea water (marine corrosion, aqueous corrosion) is not a mechanical but an electrochemical process. 

Rock breakdown by salt weathering takes place through salt crystal growth in rock pores and/or through hydration of hydrate forming salts, like sodium sulphate (Na2SO4 -> Na2SO4.10H2O). The expanding salt crystals exert a pressure on the walls of the rock pores that exceeds the tensile strength of the rock. In the following paper a series of experiments with a climatic cabinet is described and discussed aimed at elucidating the mechanism of salt weathering. The experiments were carried out at the Department of Physical Geography and Soil Science, University of Amsterdam, The Netherlands.

Click  here  to download the paper in pdf-format (3,3 Mb).

Here is an example of salt weathering of granite at the French Mediterranean coast near St. Tropez.

Marine abrasion of granite preceded and facilitated by rock disintegration through salt weathering in the surf zone (French Mediterranean coast near St. Tropez).

In the following pictures, details are shown:

Developing salt crust through evaporation of salt brine in the surf zone.

Crystallized salt on the rock surface and in rock fissures in granite in the surf zone.

Rock particles released by salt weathering of granite in the surf zone.

Rock particles released by salt weathering of granite in the surf zone. 

Salt weathering links
My name is Frans Kwaad, former lecturer in geomorphology, Dept. Physical Geography and Soil Science, University of Amsterdam, The Netherlands.

Weathering on Mars
Click here for some very interesting images of rock breakdown on the surface of Mars, presented by Heather Viles.

Full online-texts
Stone conservation: an overview of current research - Doehne and Price, 2010 (full pdf-text of book, 86 pp.)
Rock weathering in Central Spitsbergen and in Northern Victoria Land (Antarctica) - Angelique Prick and others, 2004 (full pdf-text)
Roads and salinity - NSW Australia, 2003 (full pdf-text)
Influence of salt weathering on the properties of concrete - Mokhtar M. Aburawi and R.N. Swamy, 2008 (full pdf-text)
Salt weathering distress on concrete exposed to sodium sulfate environment - Harvey Haynes and others, 2008 (full text)
Salt weathering of masonry walls: the Venice experience - Collepardi and others (full pdf-text)
Fracture of porous materials induced by crystallization of salt - Katzoff, 2004 (full pdf-text)
Salt damage in porous materials: an RH-XRD investigation - Linnow, 2007 (full pdf-text)
Salts in the deterioration of porous materials: an overview - Charola, 2000 (full pdf-text)
Transport and crystallization of dissolved salts in cracked porous building materials - Poupeleer, 2007 (full pdf-text, 323 pp.)
Salt deterioration and microclimate in historical buildings - Bionda, 2004 (full pdf-text)
Stone properties and weathering induced by salt crystallization of Maltese Globigerina Limestone - Rothert et al., 2007 (full pdf-text)
The thermal expansion and crystal structure of mirabilite (Na2SO4.10D2O) - Brand and others, 2008 (full pdf-text)

Other links
Corrosion doctors
Marine corrosion
Marine corrosion forum
Salt weathering of medieval stone cave ruins: Example of Yagura's in Kamakura, Central Japan - Kawano Tatsuyasu and Kosaka Kazu, 2002
Weathering damage on pharaonic sandstone monuments in Luxor, Egypt - Bernd Fitzner and others (pdf-abstract, 2003)
Salt weathering: a neglected geological erosive agent in coastal and arid environments - Wellman and Wilson, 1965
Crystal growth during the hydration of CaSO4.1/2H2O - Chatterji and Jeffery, 1963
The influence of petrophysical properties on the salt weathering of porous building rocks - Benavente and others, 2007
Influence of capillary properties and evaporation on salt weathering of sedimentary rocks - Angeli and others, 2006
Surface recession by salt-weathering-induced granular disintegration of porous building stone in central Michigan - Velbel, 2006
Salt weathering of airoplanes - Fred R. Boucher
Salt weathering on buildings and stone sculptures - Conference Copenhagen, Denmark, 2008
Salt weathering on buildings and stone sculptures - Conference 2008 Copenhagen, Denmark
Heritage, weathering and conservation - Conference proceedings 2006
Salt decay of sandstone, 1999
Salt weathering: a selective review, 2002
Salt weathering and tafoni
Papers on salt weathering
Stone decay in central Oxford
Salt weathering hazards - Goudie and Miles, 1997
Salt research: mechanisms of salt decay and methods of mitigation
Assess to what extent salt is an aggressive agent in the breakdown of rock and engineering structures in arid regions. What factors can be adopted to combat such problems? - Cathy Davies
Understanding stone decay