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Opis: There is a need to develop new construction materials with improved mechanical performance and durability that are low-priced and have environmental benefits at the same time. This paper focuses on the rheological, mechanical, morphological, and durability properties of synthetic and steel fiber reinforced self-compacting concrete (SCC) containing 5–15% metakaolin (M) by mass as a green replacement for Portland cement. Testing of the fresh mixes included a slump-flow test, density, and porosity tests. Mechanical properties were determined through compression and flexural strength. A rapid chloride penetrability test (RCPT) and the chloride migration coefficient were used to assess the durability of the samples. A scanning electron microscope (SEM) with energy dispersion spectrometry (EDS) was used to study the concrete microstructure and the interfacial transition zone (ITZ). The results show that a combination of metakaolin and hybrid fibers has a negative effect on the flowability of SCC. In contrast, the inclusion of M and hybrid fibers has a positive effect on the compressive and flexural strength of SCC. The fracture of SCC samples without fibers was brittle and sudden, unlike the fiber-reinforced SCC samples, which could still transfer a considerable load with increasing crack mouth opening deflection. Overall, the chloride migration coefficients were reduced by up to 71% compared to the control mix. The chloride reduction is consistent with the resulting compact concrete microstructure, which exhibits a strong bond between fibers and the concrete matrix.
Ključne besede: self-compacting concrete, synthetic and steel fibers, metakaolin, rheology, mechanical properties, chloride penetration, SEM-EDS
Objavljeno v DKUM: 12.03.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (6,46 MB)
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Opis: This study explores the potential of using basalt reinforced UHPC by incorporating simulta- neously self-cleaning and self-luminescent features, paving the way for sustainable advancements in civil engineering. New green formulations of UHPC were developed by integrating supplementary cementitious materials and optimizing water to the binder ratio, followed by using basalt fibers to enhance strength and ductility. The fabricated samples with high particle-packing density exhibit sufficient workability and compressive strength up to 136 MPa, and, when incorporating basalt fibers, a notable reduction in brittleness. The inner microstructure of basalt fibers was observed to be smooth, homogeneously distributed, and well adhered to the UHPC matrix. To ensure the desired long-lasting visual appearance of decorative UHPC and reduce future maintenance costs, a time-effective strategy for creating a light-emitting biomimetic surface design was introduced. The samples exhibit high surface roughness, characterized by micro to nano-scale voids, displaying superhydrophobicity with contact angles reaching up to 155.45◦. This is accompanied by roll-off angles decreasing to 7.1◦, highlighting their self-cleaning features. The self-luminescence feature showcased intense initial light emission, offering a potential energy-efficient nighttime lighting solution.
Ključne besede: UHPC, basalt fibers, mechanical properties, morphology, superhydrophobic, self-luminescence
Objavljeno v DKUM: 16.10.2024; Ogledov: 0; Prenosov: 14
Celotno besedilo (12,91 MB)

Opis: This study explores the potential of using basalt reinforced UHPC by incorporating simultaneously self-cleaning and self-luminescent features, paving the way for sustainable advancements in civil engineering. New green formulations of UHPC were developed by integrating supplementary cementitious materials and optimizing water to the binder ratio, followed by using basalt fibers to enhance strength and ductility. The fabricated samples with high particle-packing density exhibit sufficient workability and compressive strength up to 136 MPa, and, when incorporating basalt fibers, a notable reduction in brittleness. The inner microstructure of basalt fibers was observed to be smooth, homogeneously distributed, and well adhered to the UHPC matrix. To ensure the desired long-lasting visual appearance of decorative UHPC and reduce future maintenance costs, a time-effective strategy for creating a light-emitting biomimetic surface design was introduced. The samples exhibit high surface roughness, characterized by micro to nano-scale voids, displaying superhydrophobicity with contact angles reaching up to 155.45°. This is accompanied by roll-off angles decreasing to 7.1°, highlighting their self-cleaning features. The self-luminescence feature showcased intense initial light emission, offering a potential energy-efficient nighttime lighting solutio
Ključne besede: UHPC, basalt fibers, mechanical properties, morphology, superhydrophobic, self-luminescence
Objavljeno v DKUM: 29.01.2024; Ogledov: 368; Prenosov: 447
Celotno besedilo (14,47 MB)
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Opis: Ogroženost okolja in globalne podnebne spremembe so med največjimi izzivi sodobnega časa. Človeške dejavnosti, kot so izgorevanje fosilnih goriv, krčenje gozdov in intenzivno kmetijstvo, povzročajo povečanje toplogrednih plinov v ozračju, ki zadržujejo toploto in spreminjajo naravno ravnovesje. Posledice so vidne v porastu povprečne temperature zraka in oceanov, taljenju ledenikov in polarnega ledu, dvigu morske gladine, pogostejših in ekstremnejših vremenskih dogodkih ter izgubi biotske raznovrstnosti. Nujno je treba ukrepati na vseh ravneh, od lokalne do globalne, da bi zmanjšali emisije toplogrednih plinov, prilagodili se spremenjenim razmeram in ohranili naravne vire za prihodnje generacije. Analiza življenjskega cikla (LCA) je metodologija za ocenjevanje okoljskih vplivov, povezanih z vsemi fazami življenjskega cikla izdelka, procesa ali storitve. V tej študiji s pomočjo LCA-analize primerjamo proizvodnjo petih različnih izolacijskih materialov v gradbeništvu: škrobnega aerogela, silikatnega aerogela, kamene volne, steklene volne ter poliuretanske pene. Cilj analize je ugotoviti, kateri material ima najnižji okoljski odtis glede na različne kategorije vpliva. Na podlagi rezultatov lahko sklepamo, da sta škrobni in silikatni aerogel bolj trajnostni izbiri za izolacijske materiale v gradbeništvu kot kamena volna, steklena volna ali poliuretanska pena. Vendar pa je treba upoštevati tudi druge dejavnike, kot so stroški, razpoložljivost, zmogljivost in trajnost materialov pri konkretnih aplikacijah.
Ključne besede: izolacijski materiali, aerogeli, LCA
Objavljeno v DKUM: 19.06.2023; Ogledov: 528; Prenosov: 85
Celotno besedilo (2,41 MB)

Opis: V magistrskem delu je na podlagi pregledanih člankov in laboratorijskih preiskav predstavljena raziskava konoplje, konopljinega betona, izdelanih receptur apnenega konopljinega betona in materialov, ki ga sestavljajo. Raziskali smo fizikalne, mehanske in trajnostne lastnosti konopljinega betona in pripravljenih receptur apnenih konopljinih betonov z dodatki granulirane plavžne žlindre in portlandskega cementa 42,5 N, z vsebnostjo 5 % mase konopljinega pezdirja namesto agregata (zrnavosti 0/4 mm). Ugotovili smo, da na lastnosti konopljinega betona v otrdelem stanju vplivajo obdelava in sorta industrijske konoplje ter vrste uporabljenih veziv. Na otrdelih pripravljenih vzorcih smo opravili preiskave tlačnih in upogibnih nateznih trdnosti, od katerih so v obeh primerih najboljše rezultate dali vzorci z dodatkom portlandskega cementa in najslabše tisti z dodatkom mlete granulirane plavžne žlindre. Preverjali smo protimikrobno učinkovitost pripravljenih vzorcev v otrdelem stanju, kjer sta cono inhibicije razvila vzorca z dodatkom deleža cementa in dodatkom cementa skupaj z žlindro v vezivu. Od pripravljenih receptur je TGA/DSC pokazala, da ima največji masni delež CaCO3 in najmanjši masni delež Ca(OH)2 vzorec z dodatkom cementa. Ugotovili smo, da so cene konopljinih betonov v Evropi redko dostopne, močno variirajo zaradi različnih sestav in načina vgrajevanja in so posledično težko primerljive. Primerjava raziskav LCA pri različnih parametrih je dokazala, da je konopljin beton, sestavljen iz konopljinega pezdirja, veziva in vode, v svojem življenjskem ciklu ogljično negativen. Konopljin beton, ki ne vsebuje kamnitega agregata, je primeren za uporabo v Sloveniji, saj obstaja iz njega že več zgrajenih objektov, kot tudi podjetje, ki se ukvarja z gradnjo s konopljinim betonom.
Ključne besede: konopljin beton, industrijska konoplja, analiza življenjskega cikla konopljinega betona
Objavljeno v DKUM: 25.11.2022; Ogledov: 720; Prenosov: 105
Celotno besedilo (6,41 MB)