Mortar Materials in Building Conservation

Dear Colleagues,

In historic buildings, mortar materials represent the most important composite influencing their sustainability, but at the same time they are also a material carrying valuable information and significant heritage values. Sustainability research on mortar materials must study the mechanisms of their degradation and develop technologies to prevent their destruction. Climate change causes more frequent hazardous situations accompanied by extraordinary demands on the behaviour of mortar materials when they are saturated with water and subjected to repeated alternating mechanical or temperature cycles, including fires. With the onset of more intense weather conditions, it is important to learn about the durability and life cycles of conservation materials and processes that save degrading mortar materials. A persistent problem is the determination of the compatibility limits of changes in the material properties of treated materials and the methods of their testing. At the same time, we must not forget the effects of the application of these new technologies and materials on the environment and, in particular, on the health of restorers and residents. Mortar materials not only carry the monumental values of works of art on their surface, but also contain hidden information that can be revealed by scientific methods. These include, for example, the determination of the age of the material from the time of production, the determination of the provenance of the components, including the raw material, and the technological traces of production and construction, e.g., formwork fingerprints. The results of basic and applied research in these areas are welcome to be contributed to this Special Issue.

Prof. Dr. Miloš Drdácký
Prof. Maria Stefanidou
Guest Editors

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• impact of climate and weather on mortar characteristics and durability
• mortar and plaster degradation mechanisms
• mortar resilience during exceptional loading or environmental situations
• conservation materials and procedures improving mortar materials behavior
• in situ testing of mortar qualities before and after conservation interventions
• lifecycles of efficiency of mortar conservation, protection, or strengthening materials
• mortar conservation with reduced health risks
• mortar materials as an information carrier

Title: Influence of CO2 environment on the properties of natural fiber-reinforced lime mortars
Author: Stefanidou
Highlights: 1. The possitive role of bio-fibres in lime mortars 2. The improved properties in lime mortars produced by hot-lime technology 3. The positive effect of accelarated carbonation on mechanical properties of lime mortars 4. Hemp fibre reinforced lime mortars using quicklime and cured in high CO2 environment present increased strength

Title: Degradation mechanisms of mortar layers
Authors: Miloš Drdácký; Radek Ševčík; Dita Frankeová; Veronika Koudelková; Jaroslav Buzek; Marek Eisler; Jaroslav Valach
Affiliation: Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Department Heritage Science
Abstract: The article presents a case of complex investigation of defects of lime mortar and plaster that have been developing over a period of 48 years in a house in Prague, and that are strongly influenced by thermal and salt crystallization cycles. The aim of the research was to describe the degradation phenomena of mortars and plasters observed on a narrowly limited part of the building combining structural elements of different types and ages and to explain the mechanisms of their formation and development. The geometric characteristics of the defects were determined by non-destructive methods, especially optical interference moiré, laser profilometry, photogrammetry and infrared thermography. Material data was determined on samples by electron microscopy, ion exchange chromatography and direct moisture content measurements. The results supported the hypothesis of the increase in the deformation of large buckles of detached plasters by the mechanism of buckling caused by loading of the edges with compression generated by volume changes. Direct loading of the boundary surfaces causes the formation of the bulges in the confined areas. The study shows the importance of failure analysis of real structures to gain knowledge about the behavior of structures and materials under long-term service conditions.