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SALT CRUST - EFFLORESCENCE
SALT CRUST - EFFLORESCENCE

Sample

Church of the Monestir d’Aviganya.  Ntra. Sra. del Remei Chapell. LLeida. Spain.


Pathology Causes

Alkaline salts (potassium and sodium sulphates) from the cement used in the repairs of the Church roof have leaked in the walls of the building. These salts have also reacted with the components of the stone, especially with the dolomite mineral, generating new salts of different composition, magnesium sulphates (hexaedrite). The two processes have combined to accelerate the process of alteration (synergic effect).


Visual Image

Author: CETEC-patrimoni

Description: Efflorescence and salt crust on stone ashlars associated with damp patches due to leaks from the roof.


Image detail / macro

SALT CRUST - EFFLORESCENCE
Author: CETEC-patrimoni
Magnification: 20 x
Description: Crystal aggregates of white colour and irregular size and shape. They present different crystalline forms: needle-like, rounded, and fibrous.

Microscope Image

SALT CRUST - EFFLORESCENCE
SALT CRUST - EFFLORESCENCE
Author: CETEC-patrimoni
Magnification: Figure 1. SEM-BSEI-image x100. Figure 2.- SEM-BSEI-image x2000
Description: Figure 1. There are two types of crystalline aggregates. The first one is a needle-like or lenticular gypsum tablets. The second one is a crystalline aggregate with crystals rounded or globular composed of magnesium sulphate.
Figure 2. Dolomite crystal altered by chemical reaction with the salts of cement, generating new magnesium salts

Associated Pathologies

Flaking.

Sanding.

Alveolization.


Other Tests

XRD. Efflorescence of gypsum and hexaedrite.

Observations

Efflorescence of gypsum and hexaedrite showing that dolomite crystal has been altered by chemical reaction with the cement salts, generating new magnesium salts.

Bibliography

CARNER, E.N.; DERMICI, S; TURKMENOGLOU, A.G. Deterioration of dolomite by soluble salts in Divrigi Great Mosque –Turkey. V Th. Int. Congrees on deterioration on conservation of stone. Lausanne 1985.

 

MADRUGA, F.; SAAVEDRA, J.; MARTIN PATINO, M.T.  Eflorescencias y costras sobre areniscas de

Villamayor. Ensayos de laboratorio. Materiales de Construcción, vol 44, nº 234. 1994. doi:10.3989/mc.1994.v44.i234.587

Author

Jose Luis Prada Pérez. prada43@wanadoo.es

Geologo


Institution or Company

ESCRBCC


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