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ASHLAR PERIPHERAL CRUST
ASHLAR PERIPHERAL CRUST

Sample

Figure 1. Roman Wall of Tarragona. Spain.
Figure 2. Roman Amphitheatre of Tarragona. Spain.

Pathology Causes

This peripheral crust has originated from two combined processes: an intense differential erosion inside the stone and a reaction with the hydraulic repair mortars. These mortars generate the neoformation of dolomite (and other minerals) in the peripheral, hardening the outer sides of the ashlars.


Visual Image

Author: J.L.Prada
Description: Millimeter crust of hardened stone in the periphery of the ashlar.

Image detail / macro

ASHLAR PERIPHERAL CRUST
Author: J. L. Prada
Magnification: x10

Description: Detail of the peripheral crust. (A) Mortar, (B) crust, (C) ashlar with granular disintegration.


Microscope Image

ASHLAR PERIPHERAL CRUST
ASHLAR PERIPHERAL CRUST
Author: J.L.Prada
Magnification: Figure 1. x200. Figure 2. x1080
Description: Figure 1. Neoformation of dolomite crystals in the peripheral crust ashlar. Petrographic microscope image.
Figure 2. Neoformed dolomite crystals are compact, homogeneous and without zoning.

Associated Pathologies

Alveolization.

Flaking.

Sanding


Other Tests

XRD analysis

Observations

The table summarizes the XRD analysis indicating that the peripheral crust contains more dolomite than the rest of the stone.

Bibliography

CANER, E.N.; DERMICI, S.; TURKMEMOGLOU, .A.G. (1985). Deterioration of dolomite by soluble salts in Divrigi Great Mosque – Turkey. V Th. Int. Congrees on deterioration on conservation of stone. Lausanne, 1985.
 
PRADA, J. L. (1995) Caracterización de Formas y Procesos de Alteración observados en Piedra de Construcción de Edad Miocénica del Área Monumental Romana de Tarragona". PhD.


Author

Jose Luis Prada Pérez. prada43@wanadoo.es

Geologo


Institution or Company

ESCRBCC


Published Articles

PRADA, J.L.; VALENCIANO, A.; NAVARRO, A. (1995). Procesos de alteración de materiales pétreos en edificios de interés histórico. Acta GeolÓgica HispÁnica, vol 30, nº 13. Universidad de Barcelona. pp. 97-110.
 
PRADA, J.L.; VALENCIANO, A. (1995). Alteración de unas dolomitas zonadas del Miocéno de Tarragona. XVII Reunion Bienal de la Sociedad Española de Microscopía Electrónica. Oviedo. pp. 282-283.

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