Investigation of mortars from historical monuments of North-East Poland and assessment of compatibility between historic and restoration mortars

This study aims to provide insight into the properties of existing historical brick masonry structures through an integrated physical, microstructural and hygric characterization of masonry binders used in five monuments from northeast Poland in order to maintain as much as possible the original traditions and to provide appropriate conservation strategies. The analytical characterization of historic mortars was carried out by means of laboratory tests, such as density, grain size analysis, water absorption and capillary absorption coefficient. In order to assess the microstructural and chemical characteristics of the tested samples, XRF, XRD, optical microscopy and mercury intrusion porosimetry (MIP) tests were performed. These tests were conducted on mortars from medieval and Baroque buildings of great historic significance as well as on currently produced repair mortars in order to identify the similarities and differences between specific groups of material properties. The results of this study will contribute to evaluating the compatibility of repair materials with those historically used in terms of moisture, microstructure, mineralogical composition and mechanical properties to achieve successful restoration work. Moreover, the findings may enhance modeling programmes, which can help simulate, as closely as possible, humidity transfer in real conditions. • Physical, microstructural and hygric analysis of masonry binders from historic monuments in northeast of Poland. • Comparison of historic and modern mortars to assess compatibility for restoration. • Knowledge of brick wall materials by period to support effective repair planning. • Input data improves simulation of real moisture behavior in historical structures. • Input data for modeling humidity transfer in real conditions.