In situ investigation of stone heritage sites for conservation purposes: a case study of the Sz\xe9kesfeh\xe9rv\xe1r Ruin Garden in Hungary

Magdalini Theodoridou,Ákos Török

doi:10.1186/s40645-019-0268-z

Abstract

This paper demonstrates the application of in situ diagnostic tools to document stone heritage sites prior to conservation interventions using a Medieval ruin of Central Europe (Székesfehérvár, Hungary). The applied methods included lithological mapping and characterisation and mapping of decay forms as well as in situ measurements of physical parameters such as Schmidt hammer rebound, moisture content and micro-drilling resistance. The combination of these methods allowed the condition assessment of different lithotypes and demonstrated the role of micro-fabric, mineralogical composition and climatic conditions in stone durability. Differences were found in the properties and in the weathering forms of fine-grained and medium-grained porous oolitic limestone and travertine. The black crust observed in porous limestone is less prone to detachment on medium-grained oolitic limestone ashlars, while scaling was observed on fine-grained oolitic limestone blocks. The micro-drilling resistance of exposed porous limestone showed higher drilling resistance at the crust zone (upper 1–2 mm) than below, marking the upper cemented zone, while the drilling resistance of porous limestone under shelter showed an opposite trend. The shelly limestone, the sandy calcarenite and red compact limestone also showed an increase in drilling resistance at the topmost app. 2 mm zone. The applied in situ, non-invasive and micro-destructive techniques helped in the identification of endangered zones at Székesfehérvár, thus, they can provide key information on condition assessment of stones at heritage sites, where sampling is limited and preventive conservation is important.

Highlights

Tangible cultural heritage such as ruins or stone buildings needs special attention in terms of preservation and documentation (Jokilehto 1999)
Based on micro-fabric analyses, it is very probable that oolitic limestone (OL), which was used at Székesfehérvár, was quarried in Budapest region (Török 2002), while shelly limestone (SL) and sandy calcarenite (SC) came from Öskü area (Török 2004a)
The mapping method presented in this paper proved to be very useful for the identification of the site, such as the documentation of the different lithotypes used over the different construction periods, the record of the in situ measured values and their ensuing interpretation in relation with the existing climatic conditions and the correlation of the identified weathering forms with the different lithotypes

Summary

Introduction

Tangible cultural heritage such as ruins or stone buildings needs special attention in terms of preservation and documentation (Jokilehto 1999). The present study focuses on the diagnostics of a medieval ruin garden located in Hungary It focuses on the geological composition of materials, exposure and air pollutants, as well as previous construction activities. The monument, which is comprised of different construction materials (e.g. various stones and mortars), needs a complex diagnostic approach. In this case, the role of earth scientists is crucial (Přikryl 2007). The diagnostic survey can have a very broad context referring to geotechnical studies concerning the ground support and groundwater table; geomaterials characterisation from lithological description to detection of weathering forms and to measuring on site physico-mechanical properties and mineralogical and chemical composition.

Results

Discussion

Conclusion