Experimental study of Chemical deterioration

of Chellah Monument stones

 

A. Samaouali1*, L. Laanab3, Y. Geraud4, A. Nounah2, M. Boukalouch1

1  Laboratoire de Thermodynamique, Département de Physique, Faculté des Sciences,  B. P. 1014, Rabat. Maroc

2  Laboratoire des Sciences de l’Environnement, Ecole Supérieure de Technologie, B.P. 227, Salé Médina, Maroc

3  Centre de Microscopie, Département de Physique, Faculté des Sciences, B. P. 1014, Rabat. Maroc

4 Ecole et Observatoire des Sciences de la Terre, Université Louis Pasteur,

Institut de Physique du Globe Strasbourg UMR 7516, 1 rue de  Blessing,  F-67084 Strasbourg Cedex, France

* Corresponding author. E-mail: samouali@fsr.ac.ma

Received: 26 June 2008; revised version accepted: 30 October 2008

 

 

Abstract  

    The stones of the site monument Chellah Roman are mainly made up of limestone resulting from a quarry of the Rabat area (Morocco). They are made up in majority of Calcium Carbonate. In the course of time, these stones underwent much chemical deterioration which is responsible for the degradation of these monuments. The major chemical weathering is the dissolution of calcium carbonate by rainwater, favoured, on the one hand by the solubility of calcite in aqueous medium, and on the other hand, by the action of the acids present. In this work, we undertake a structural study, based on Scanning Electron Microscopy coupled to Energy dispersive

     X-ray spectrometer (SEM-EDX) and X-ray diffraction, on the stones Chellah monument. The objective is to highlight the structural and chemical difference between the altered and unaltered samples. The stones studied present various structural, morphological and chemical properties, which can be explained throughout a mechanism of dissolution of the calcite bringing into, play various chemical reactions. This mechanism is mainly activated by the filtration of rainwater accompanied by an increase in the acidity of the medium.

 

Keywords:  Calcarenite rocks decay; Dissolution calcite; Chemical weathering.

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