[M-IS07] Geomaterials in cultural heritage: weathering, investigation techniques, and conservation

[MIS07-P04] Moisture and salt distribution in thick porous limestone walls of built heritage, examples from Budapest

*Akos Torok¹、Annamária Kis¹ (1.Department of Engineering Geology and Geotecnics, Budapest University of Technology and Economics)

キーワード：salt, weathering, moisture, limestone, cultural heritage

Limestone walls often suffer from salt weathering and salt crystallisation is of the main mechanisms that lead to stone decay. The trigger factors of the deterioration and salt crystallization are linked to moisture content and mobilisation of salts. The present study focuses on the moisture distribution of limestone walls, using a case study from Budapest (capital of Hungary). The studied building, a fortress was constructed from highly porous (up to 35% porosity) marine limestone of Miocene age. It is located on a hilltop and exposed to wind that regularly brings moisture in the form of rain, snow. Foggy periods also occur during autumn. Moisture distribution and salt content of the ashlars were tested. The measurements were made at the surface of the walls along vertical profiles seasonally, to understand the differences in moisture distribution between hot summer and cold winter periods. Small drillings were also made to detect the in depth moisture content of the walls. The distribution and composition of the salts were recorded. Drilled samples and surface samples collected from the wall were analysed. Applied techniques included textural analyses by microscopy, elemental analyses by XRF and mineralogical compositional tests using XRD and thermogravimetry. The moisture and salt distribution clearly linked to seasons, show significant changes in between summer, and winter period. The observed trends help in understanding the seasonal changes in salts and allow to assess the seasonal differences in salt weathering not only in porous limestone but also in other lithologies.