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Povzetek: This study focuses on the kinetics of hydration, phase assemblage, microstructure and mechanical properties after various hydration times of two different BCSA cements at 5, 20, 40 and 60 ◦C and compares experimental data with thermodynamic modelling. Different curing temperatures change the type of hydrates and their amounts. Ye’elimite and gypsum in belite-ye’elimite-ferrite cements are almost fully reacted after 24 h of hydration at 20, 40 and 60 ◦C, while not at 5 ◦C. The hydration of belite is slower than the one of ye’elimite, but reaches a high degree of hydration after 150 days which is increasing with temperature. Less ettringite is present at elevated temperatures due to its increasing solubility, while more monosulfate is observed. Furthermore, with increasing temperature siliceous hydrogarnet forms at the expenses of strätlingite as well as more C S H is found as more belite reacts resulting in higher compressive strength. Dense and homogenous microstructure is observed at 5 ◦C, while it is more heterogeneous at higher temperatures. The presence of more ye’elimite resulted in higher ettringite and str¨atlingite formation and a higher compressive strength, while more belite yields more C S H in the hydrates and lower compressive strength.
Ključne besede: belite-ye’elimite-ferrite cement, temperature, hydration, thermodynamic modelling
Objavljeno v DiRROS: 11.12.2023; Ogledov: 170; Prenosov: 142
Celotno besedilo (9,96 MB)
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Povzetek: In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO2/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO2/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility.
Ključne besede: photocatalytic coating, consolidant, protection, conservation, porous substrate, cultural heritage
Objavljeno v DiRROS: 21.11.2023; Ogledov: 235; Prenosov: 175
Celotno besedilo (2,55 MB)
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Povzetek: The present study deals with the characterisation of pigments used in two overlaid gothic wall paintings from the former 13th century Minorite church of St. Francis of Assisi (Koper, Slovenia), in order to define differences in the technologies used. Paint layer samples were analysed via Raman microspectroscopy, supported by SEM/EDS and FTIR analysis, when necessary. The results revealed that the 14th century mural was painted mainly a fresco with final elements a secco, a technique typical of Italian mediaeval wall painting. In contrast, the 15th century painting was executed mostly a secco, a technique often applied in Northern Europe and the Alpine region. The differences between the two paintings are especially obvious in the pigments applied. While the earlier painting is characterised by azurite, carbon black, red and yellow ochres, lime white and green earth, the palette used for the younger painting is much broader. In addition to red and yellow ochres, carbon black and lime white, lead pigments such as lead white, red lead and lead-tin yellow type I were also determined, as well as a number of expensive pigments including cinnabar, azurite and malachite. Also found in the younger painting was the rare orange yellow pigment vanadinite. In both layers, azurite was applied a secco for the background area. Gilding was confirmed in both layers, carried out as application of gold leaves on red bole (in the earlier mural) and on mordant (on a younger, superimposed (overlaid painting), which is quite exclusive and rare for Slovene mediaeval painting. In the younger layer also a use of tin foil for secondary elements was discovered.
Ključne besede: wall paintings, pigments, Gothic, golding, Raman microspectroscopy
Objavljeno v DiRROS: 27.10.2023; Ogledov: 398; Prenosov: 161
Celotno besedilo (4,58 MB)
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Povzetek: Not only is the energy efficiency of buildings nowadays becoming more and more important; the legislative requirements, the people’s awareness of the environmental questions and their thermal comfort expectations are also on a much higher level. All of these issues can be addressed by making the building envelope more thermally resistant. However, with the traditional thermal insulation materials the thickness of thermal insulation layers is already at the viable limits. Therefore, the development of new, more efficient thermal insulation products with a higher thermal resistance is highly promoted. Preliminary research results can be applied to models to develop and confirm the conceptual designs of such new materials. In this paper, an analysis of thermal performance is presented for a novel thermal insulation consisting of graphite polystyrene (GPS) matrix with cavities filled with an insulative gas, and a protective sheath to prevent it from leaking. Bearing in mind the suitability for later production, different configurations of the assembly were considered, regarding the matrix geometry, the type of the gas filling, and the surface emissivity of the cavities. A range of numerical simulations of heat transfer was conducted to determine the efficiency of different designs in reducing the conductive, the convective, and the radiative heat transfer. Advantages, limitations and some detailed parameters of the proposed design concepts were determined, which were then used for optimisation. The analysis of the results indicates that the equivalent thermal conductance of a GPS panel can be significantly reduced by the introduction of gas-filled cavities. The reduction is highly dependent on the type of the gas filling (thermal conductivity, viscosity, specific heat, etc.), the size of the cavities, and the cavity surface emissivity.
Ključne besede: gas-filled cavities, graphite polystyrene, numerical simulation, thermal insulation
Objavljeno v DiRROS: 15.09.2023; Ogledov: 262; Prenosov: 122
Celotno besedilo (1,21 MB)
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Povzetek: Novel prefabricated insulating façade panels were developed from construction and demolition waste (CDW) aggregates under the framework of the European H2020 project InnoWEE. These non-structural components, aimed at improving the thermal efficiency of existing buildings, consist of an insulating plate covered by a facing layer made of CDW aggregates bound with metakaolin, furnace slag and class F fly ash activated by a potassium silicate solution. The paper presents the design and assessment of the binder and panels for exterior use, taking into account mechanical performance, behaviour in the presence of water and durability issues. Testing was carried out on both laboratory prototypes and panels from the pilot industrial production.
Ključne besede: construction and demolition waste, alkali activated materials, geopolymers, properties, up-scalimg
Objavljeno v DiRROS: 21.08.2023; Ogledov: 265; Prenosov: 143
Celotno besedilo (2,99 MB)
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