POROUS NETWORK STRUCTURE AND TOTAL POROSITY OF ROCKS USED IN HISTORICAL MONUMENT CHELLAH

The aim of this work is to determine the physical and mineralogical characteristics of the building stones used In the archeological Roman site named Chellah In the Rabat city (Morocco). For that, many experimental measurements, based on the mercury Intrusion porosimetry and Scanning Eelectron Microscopy were carried out on samples extracted from different areas of the building. The SEM analysis shows a net change in the Internal structure of the altered stone according to the depth. The porosity is essentially localized between the primary particles and can be completely sealed by secondary precipitations. The mercury porosimetry measurements allow obtaining several parameters and show the presence of three types of porosity domains :1) a macroporosity domain In which the access ray is greater than 2 mu m), II) a microporosity domain In which the access ray Is smaller than 0.2 mu m and III) no porosity variation (0.2 < access ray < 2 mu m), which evolves to a class of mesoporosity during the alteration of the material. The increase in the microporosity and macroporoslty is caused by a partial dissolution of cements. The analysis of altered and unaltered samples of various orientations shows a difference between the pore volumes for samples perpendicular and parallel to the bedding plane. This result confirms that Calcarenite stones are anlsotroplc materials in which the porous network connectivity is characteristic of the petrophysical properties anisotropy.