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Documentation and examination of historic building materials for the purpose of conservation : case study, part of the walls at the citadel of Ankara

Tokmak, Musa
The study aimed to identify deterioration problems, repair and conservation needs of andesites on the walls of the Ankara Castle. Decay forms of walls were documented by visual examination. Samples taken from the surface of the weathered andesites were examined for their basic physical, mechanical compositional and minerological properties. The bulk density and total porosity were determined as basic physical properties. The mechanical properties were expressed as ultrasonic velocity and modulus of elasticity (Emod). Compositional and mineralogical properties were determined by optical microscopy and XRD analyses. Soluble salt content of the andesite samples was determined by spot tests of anions and electrical conductivity measurements. Findings were evaluated in terms of the long-term weathering behaviour of andesites under the effect of the prevailing climate, air pollution problems of Ankara, dampness problems of the structure, previous repairs with incompatible cement mortars. The surfaces of Ankara Castle andesite blocks were heavily weathered. The results were compared with the physical and mechanical properties of fresh andesites from G_lbasi-Ankara quarry. The surface of the andesite blocks at the Ankara Castle, had low bulk density and high porosity, low ultrasonic velocity and low Emod values. Thin section and XRD analyses supported those results by revealing the presence of physical and chemical weathering on feldspars and other main minerals of andesite, as well as the presence of amorphous minerals at the surface.