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Povzetek: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Ključne besede: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Objavljeno v DiRROS: 22.11.2023; Ogledov: 307; Prenosov: 146
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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: 265; Prenosov: 184
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Povzetek: We live in a material world where the markets are flooded with all kinds of products. At the same time, we are facing a population growth, as well as a product demand growth. But, are we aware of the raw materials needed for our favourite daily products? In which part of the world are they extracted? Do we recognize the value chains from the mine to the product? And, where do these products end up after we use them? Many school curriculums include this topic only briefly, thus there is a need to raise awareness among youngsters about mining and raw materials in general. EIT RawMaterials funded by the European Commission, is the largest community dealing with raw materials in Europe. One of its main objectives is to raise awareness among general public about the raw materials and their indispensability, about the consequences of their uses, about the mining and production systems as well as about the utilization and recycling. Innovative and attractive pathways are employed in the process. One of the projects bringing raw materials and mining closer to pupils is the BRIEFCASE project. Using non - conventional teaching methods, tools and guided workshops, the project provides pupils with a unique hands - on experience. It draws their attention to raw materials and their applications and helps pupils recognize minerals in products we use every day. Besides emphasizing the importance of minerals in our everyday life and addressing sensible issues like conflict minerals, the consequences of our purchase decisions, the sustainability of mining operations and their environmental implications are also presented.
Ključne besede: Project BRIEFCASE, minerals, raising awareness, non-conventional teaching tools, EIT RawMaterials, award
Objavljeno v DiRROS: 21.11.2023; Ogledov: 820; Prenosov: 155
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Povzetek: Nonwoven geotextiles are often used in road construction as a separation layer. They consist of the web of fibers with different orientations. The orientation of fibers has an important influence on physical and mechanical properties of nonwoven geotextiles. The production of nonwoven geotextiles is cheaper in comparison to woven or knitted fabrics which can also be used as separation geotextiles. The purpose of this research was to study the influence of structural properties of nonwoven geotextiles, namely the diameter of fibers and mass and thickness of nonwoven geotextiles, on their mechanical and hydraulic properties. Six types of nonwoven geotextiles were used in the research. They were produced by the drylaid process (carded) using mechanical bonding technique and also with the combination of mechanical and thermal bonding technique. The research confirmed that the bonding technique and structural properties significantly influence the separation and filtration properties of nonwoven geotextiles, such as opening size and water permeability. It was also found that there are no significant differences in mechanical properties, such as viscoelastic properties and compression creep, between the samples in the dry and wet conditions.
Ključne besede: nonwoven geotextiles, bonding techniques, opening size, water permeability
Objavljeno v DiRROS: 16.11.2023; Ogledov: 413; Prenosov: 156
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Povzetek: Chromium-molybdenum steel (16Mo3) is widely used in petroleum, gas, automotive, and construction industries due to its good oxidation resistance and mechanical properties at moderately elevated temperatures. The aim of the research was to evaluate the corrosion susceptibility of 16Mo3 steel in hot rolled and aluminized states. Aluminization was performed by diffusion pack aluminization process at 900°C/2h and 730°C/4h, respectively. Electrochemical corrosion testing included measuring open circuit potential (EOCP), linear polarization resistance (LPR), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in potassium phosphate buffer (KH2PO4, pH = 7). Optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were used for surface layer microstructure characterization before and after corrosion tests. It was demonstrated that corrosion resistance of aluminized steel increased substantially. Corrosion properties were related to the structure and properties of intermetallic phase (FeAl, FeAl2 and Fe2Al5) that formed on the surface of 16Mo3 steel.
Ključne besede: aluminide coatings, aluminized steel, aluminizing, electrochemical corrosion investigation, 16Mo3 steel
Objavljeno v DiRROS: 16.11.2023; Ogledov: 388; Prenosov: 182
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