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Archaeometrical investigation of mud plasters on Hittite buildings in Şapınuwa-Çorum

Güdücü, Gülnur
The study aimed to identify mud brick and mud plaster technology of Hittites by examining some burnt mud brick walls of Shapinuwa Hittite city and to point out repair and conservation needs of those burnt mud brick structures. The walls were documented by mapping the visual decay forms. The bulk density, total porosity, water absorption by capillarity and water vapour permeability were obtained as basic physical properties. The mechanical properties were expressed by the modulus of elasticity and the uniaxial compressive strength. Compositional and mineralogical properties were determined by optical microscopy, XRD, TGA and SEM coupled with EDX, and by XRF analyses. In addition, pozzolanic activity of powdered samples was determined.. The samples studied had low bulk density, high porosity and high water vapour permeability. The Emod values and the UCS values showed that their mechanical properties were comparable with some historic mortars and bricks. The petrographic and mineralogical analyses of burnt materials indicated a mud brick composition containing fine and medium sized siliceous aggregates mainly composed of quartz. The binder was concluded to be composed of kaolinite illite and micritic calcite that indicated the use of ideal soil compositions by Hittites to make lime stabilized mud bricks, in terms of today standards. The temperature during the fire was estimated to be around 700-800 C. The high pozzolanicity of burnt mud bricks and plasters, provided an opportunity to repair the structure using pozzolanic lime mortars to produce good adhesion. The first results of consolidation treatments had shown that the physical and mechanical properties of burnt mud brick can be improved by impregnation with ethylsilicates such as Tegovakon V.