Study of mineralogical, chemical and geotechnical properties of the historic materials for restoration of the Kutubiyya Mosque

Abstract

The preservation of built heritage represents a cultural and scientific challenge of great significance, particularly as many historical monuments in Morocco have suffered extensive deterioration. Given that the renovation of facade and interior plasters is among the most common tasks in restoration projects, it is crucial to analyze the composition of stones and plasters to ensure the compatibility of materials and their effective interaction with the substrate. In this context, our study focuses on characterizing the stone and plaster from the enclosure of the Kutubiyya Mosque in Marrakech, as well as the materials used in its restoration. To achieve this, we applied mineralogical, chemical, and petrographic characterization methods, including X-ray diffraction (XRD), X-ray fluorescence (XRF), and petrographic analysis. The masonry stone of the Kutubiyya Mosque has been identified as a marly limestone with properties characteristic of hard rocks. The primary exterior plaster is composed of lime and silty sand, with a proportion of gypsum added to accelerate the setting process. X-ray diffraction analysis revealed the presence of crystalline phases in the original masonry stone, such as calcite, clays, quartz, and dolomite. Additionally, X-ray fluorescence analysis identified the major chemical elements in the plaster. These findings reveal notable differences in the chemical composition of the original and restoration materials, highlighting their influence on the quality and durability of the restoration efforts at the Kutubiyya Mosque.