Unveiling the Secrets of Ancient Waterproofing: A Multi-Analytical Characterization of Traditional Qadhad Mortar from Sira Castle, Yemen
Qadhad is one of the most prominent traditional construction materials in Yemeni architecture, it has been used for centuries in lining cisterns, roofs, and hydraulic structures due to its high resistance to water and moisture, as well as its remarkable long-term durability. This study aims to characterize and analyze the properties of traditional Qadhad used in the historic Sira Castle in Aden City, thereby providing a scientific basis for its reproduction with comparable performance in contemporary conservation and construction as a waterproofing material. Physical tests (apparent density, open porosity, water absorption, and capillary absorption), hydraulic tests (permeability and hydraulic indices), and mineralogical analyses (XRD, XRF, SEM-EDS) were conducted in accordance with international standards. The results indicated that the apparent density of the Sira Castle Qadhad reached 1740 kg/m³, while the open porosity was 19.6%. The water absorption was 11.27%, and the permeability coefficient was approximately 6.55×10⁻⁹ m/s, demonstrating an exceptional ability to resist water infiltration and an excellent balance between density and durability. The mineral analyses (XRD and XRF) revealed the mineralogical and chemical composition of the Qadhad, while SEM-EDS micrographs showed its dense microstructure formed by calcium and aluminum hydrate gels that fill the pores, granting the material outstanding waterproofing performance that has endured for centuries in coastal environments.
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