[M-IS09] Weathering and conservation of cultural heritage and geosites

[MIS09-P03] Material properties and durability of stone in a medieval fortress; lessons to learn: an example from Hungary

*Akos Torok¹, Benedek Lógó¹ (1.Budapest University of Technology and Economics)

Keywords:basaltic tuff, physical properties, condition assessment, medieval

The material use of Medieval structures justifies the local knowledge and experience of the builders. Studying material properties and construction technology helps to understand medieval skills and expertise. In this study, the stone and renders of a 14^th to the 15^th-century fortress is presented. The fortress is located at Balaton Highland at Nagyvázsony (Hungary). It has an emblematic 25 m high tower, which was used as a living quarter. The fortress is surrounded by a system of external walls, while the tower is in the courtyard. The structure was mostly built from stone but rammed earth was also used for the interior parts of the wall. Stone, render were studied on-site using various non-destructive techniques. Surface strength of materials was tested by Schmidt hammer and Duroskop while moisture content was measured on-site with a portable device. Petrology of lithotypes was identified on site using a portable microscope. Samples were also taken for laboratory testing. Physical and mechanical properties such as density, ultrasonic pulse wave propagation, uniaxial compressive strength (UCS) and indirect tensile strength (Brasilian) test were measured in laboratory conditions according to EN and ASTM standards. Samples were measured in dry and water-saturated conditions. According to lithological description and laboratory tests, the prevailing lithotypes are basaltic tuffs, well-cemented limestone and travertine. A few ashlars of Miocene porous limestone, travertine and sandstone were also identified. The condition assessment of stone elements and laboratory tests suggest that basaltic tuffs suffered the most for weathering while other stone types seem to be more durable. This current study provides new hints to understand the medieval construction techniques and the material selection of medieval fortresses of Central Europe.