Speaker
Dr
Francesca Sciarretta
(Department of Design and Planning in Complex Environments, Università Iuav di Venezia)
Description
There is a strong demand for knowledge and diagnostics on architectural heritage buildings to be obtained mostly with non-destructive techniques, especially for large and complex assets. The motivation is to physically preserve materials and get an information picture as extensive as possible. From this viewpoint the modelling of a heritage building, be it numerical or physical or both, is recognized as a powerful tool to investigate and/or predict the real structure’s mechanical response to service and ultimate state loads. Models implement mechanical properties, which may rely on empirical data yielded from the building itself or from laboratory measurements. We aimed at establishing a multidisciplinary procedure to characterize porous historic construction materials, whose properties (physical and mechanical, as well as chemical composition) can be affected by the presence and action of water content and salt ions. The whole procedure’s objective is to relate qualitative to quantitative information, to get an evaluation of the selected material’s mechanical properties. We developed a neutron-based investigation technique to assess the condition of historic buildings’ construction materials. Neutron radiography and tomography, as well as prompt-gamma activation analysis and imaging were applied to various types of stone blocks (which can be characterized e.g. with different levels of liquid permeability in saturated conditions) to detect the uptake of water and salt ions in porous construction materials of cultural heritage significance. The results enlighten the accurate water intrusion patterns, the evaluation of the water content in unsaturated conditions, the movement of water and salt contents inside the stone samples. The established methodology may find its application niche in the non-destructive assessment of historic and contemporary building construction materials. The results of the neutron imaging (NR/NT) and elemental mapping obtained by position-sensitive neutron-based analytical techniques (PGAI, NR/NT-driven PGAI) could answer relevant scientific questions in porous cultural heritage construction materials. Among them there are the structural information for water uptake patterns from tomographic images, a time-dependence of water or salt ion solution flow in the medium, and the quantitative estimation of the spatial distribution of the water content in unsaturated conditions. The measurement and visualization of the spatial and temporal distribution is deemed useful to test and/or predict e.g. (1) the service time-dependent behavior of a weather-exposed structure or cladding, (2) the performance of materials used for restoration, for instance local substitution of cladding, (3) possible alternatives for restoration works. The time- and spatially-resolved visualization would provide a clear and immediate comprehension of stone properties even to the non-specialist, e.g. clients, accomplished or general audience interested in cultural heritage preservation.
Primary authors
Dr
Francesca Sciarretta
(Department of Design and Planning in Complex Environments, Università Iuav di Venezia)
Dr
László Szentmiklósi
(Nuclear Analysis and Radiography Department, Centre for Energy Research, Hungarian Academy of Sciences)
Dr
Zoltán Kis
(Nuclear Analysis and Radiography Department, Centre for Energy Research, Hungarian Academy of Sciences)
