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Povzetek: The production of textile-reinforced concrete (TRC) requires less materials and energy in comparison with conventional concrete reinforced with steel rebars, which draws some solutions towards the production of net zero concrete that the Cement and Concrete Industry sector should reach by 2050. To go one step further, this study investigates the development of flax based meshes as basic components for a reinforcement grid in cementitious materials. Flax strands and hybrid strands (combination of flax strands and glass or basalt rovings) were impregnated with an epoxy resin to form meshes. The physical and mechanical properties of the flax based meshes were assessed and the alkaline resistance of these reinforcing materials was evaluated to determine their durability in a cementitious matrix. At isoweight of reinforcement, the flax-based meshes demonstrated the best performance in terms of specific modulus and specific strength compared to the hybrid meshes. The hybrid meshes from the control batch displayed specific properties in the same range, whether they were constituted of AR-glass or basalt. However, the use of alkali-resistant glass rovings strongly mitigated the degradation of the mechanical properties of the hybrids meshes by making them less affected by the alkaline environment, among all the reinforcement meshes. In contrast, hybrid meshes with basalt experienced an extensive reduction in tensile strength and strain after exposure to alkaline environment, due to the corrosion of the basalt fibres. Pull-out tests revealed maximum bond strengths for the flax based meshes embedded in a high-performance concrete matrix.
Ključne besede: alkali, cement, flax, reinforcement
Objavljeno v DiRROS: 27.08.2025; Ogledov: 446; Prenosov: 215
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Povzetek: The content of leftover cement paste is a crucial parameter for determining recycled aggregates quality. Various methods assess this, including wet techniques (acid dissolution, chemical degradation, water absorption), physical approaches (freeze-thaw cycles, mechanical shredding, oven-dried density, thermal disaggregation), and spectroscopic or microscopy analyses. However, these methods often lack accuracy, are time-consuming, or depend on operator skill. A novel X-ray Powder Diffraction and Rietveld quantitative phase analysis approach is introduced to improve measurements precision. Results are compared with multi-scale analyses (microscopy, Xray computed tomography, mechanical testing) on recycled aggregate concrete specimens. Findings highlight a strong correlation between leftover cement paste content and key concrete properties, including microstructure, hydration products, and mechanical performance. This study confirms that leftover cement paste content is a decisive factor in recycled concrete aggregate properties, and that the proposed method offers a rapid and reliable approach to control this parameter.
Ključne besede: recycled concrete aggregate, leftover cement paste, CDW, X-ray diffraction, microstructure
Objavljeno v DiRROS: 27.08.2025; Ogledov: 332; Prenosov: 217
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Povzetek: We show that biholomorphic maps between certain pairs of Runge domains in the complex affine space ${\mathbb C}^n$, $n > 1$, are limits of holomorphic automorphisms of ${\mathbb C}^n$. A similar result holds for volume preserving maps and also in Stein manifolds with the density property. This generalises several results in the literature with considerably simpler proofs.
Ključne besede: Runge domains, holomorphic automorphisms, Stein manifolds, density property
Objavljeno v DiRROS: 26.08.2025; Ogledov: 271; Prenosov: 156
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Povzetek: In the photochemical reactions between MF2 (M = Cu, Ni), Ru, and F2 in anhydrous HF, Cu(RuF6)2, and Ni(RuF6)2 are formed. Only crystals of Cu(RuF6)2 are obtained during the crystallization of the powdered products. Cu(RuF6)2 crystallizes in the triclinic space group Pmathematical equation. The Cu atoms are coordinated by six F atoms, which are shared with octahedral RuF6 units. Together, they form slabs that are interconnected by van der Waals forces. In the reactions between M(RuF6)2 (M = Cu, Ni) and 2XeF2 (1:2 molar ratio), [Cu(XeF2)2](RuF6)2 and [Ni(XeF2)2](RuF6)2 are formed. They both crystallize in the monoclinic space group P21/c. The metal center is coordinated by six F atoms. Two F atoms are provided by two nonbridging XeF2 molecules, while the remaining four originate from four bridging [RuF6]- anions. In the reactions between M(RuF6)2 (M = Cu, Ni) and an excess of XeF2, [Cu(XeF2)6](RuF6)2 and [Ni(XeF2)6](RuF6)2 are formed. They are not isostructural, as the first crystallizes in the triclinic space group Pmathematical equation, while the second crystallizes in the trigonal space group Rmathematical equation. In both cases, homoleptic cations [M(XeF2)6]2+ are present, with the metal center coordinated by six nonbridging XeF2 molecules, while the [RuF6]- anions are discrete.
Ključne besede: coordination chemistry, X-ray diffraction, xenon difluoride
Objavljeno v DiRROS: 26.08.2025; Ogledov: 348; Prenosov: 175
Celotno besedilo (2,51 MB)
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Objavljeno v DiRROS: 26.08.2025; Ogledov: 368; Prenosov: 203
Celotno besedilo (6,94 MB)
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