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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: 347; Prenosov: 222
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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: 279; Prenosov: 159
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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: 350; Prenosov: 175
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Objavljeno v DiRROS: 26.08.2025; Ogledov: 373; Prenosov: 207
Celotno besedilo (6,94 MB)
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Objavljeno v DiRROS: 25.08.2025; Ogledov: 425; Prenosov: 186
Celotno besedilo (2,62 MB)
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