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Query: "author" (Mo��ina Barbara) .

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Potential of green ceramics waste for alkali activated foams
Barbara Horvat, Vilma Ducman, 2019, original scientific article

Abstract: The aim of the paper is to research the influence of foaming and stabilization agents in the alkali activation process of waste green ceramics for future low cost up-cycling into lightweight porous thermal insulating material. Green waste ceramics, which is used in the present article, is a green body residue (non-successful intermediate-product) in the synthesis of technical ceramics for fuses. This residue was alkali activated with Na-water glass and NaOH in theoretically determined ratio based on data from X-ray fluorescence (XRF) and X-ray powder diffraction (XRD) that was set to maximise mechanical properties and to avoid efflorescence. Prepared mixtures were compared to alkali activated material prepared in theoretically less favourable ratios, and tested on the strength and density. Selected mixtures were further foamed with different foaming agents, that are Na-perborate (s), H2O2 (l), and Al (s), and supported by a stabilization agent, i.e., Na-dodecyl sulphate. The goal of the presented work was to prepare alkali activated foam based on green ceramics with density below 1 kg/l and compressive strength above 1 MPa.
Keywords: alkali activation, foaming, SEM, XRF, XRD, mechanical strength
Published in DiRROS: 14.09.2023; Views: 250; Downloads: 126
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The potential of ladle slag and electric arc furnace slag use in synthesizing alkali activated materials; the influence of curing on mechanical properties
Mark Češnovar, Katja Traven, Barbara Horvat, Vilma Ducman, 2019, original scientific article

Abstract: Alkali activation is studied as a potential technology to produce a group of high performance building materials from industrial residues such as metallurgical slag. Namely, slags containing aluminate and silicate form a useful solid material when activated by an alkaline solution. The alkali-activated (AA) slag-based materials are promising alternative products for civil engineering sector and industrial purposes. In the present study the locally available electric arc furnace steel slag (Slag A) and the ladle furnace basic slag (Slag R) from different metallurgical industries in Slovenia were selected for alkali activation because of promising amorphous Al/Si rich content. Different mixtures of selected precursors were prepared in the Slag A/Slag R ratios 1/0, 3/1, 1/1, 1/3 and 0/1 and further activated with potassium silicate using an activator to slag ratio of 1:2 in order to select the optimal composition with respect to their mechanical properties. Bending strength of investigated samples ranged between 4 and 18 MPa, whereas compressive strength varied between 30 and 60 MPa. The optimal mixture (Slag A/Slag R = 1/1) was further used to study strength development under the influence of different curing temperatures at room temperature (R. T.), and in a heat-chamber at 50, 70 and 90 °C, and the effects of curing time for 1, 3, 7 and 28 days was furthermore studied. The influence of curing time at room temperature on the mechanical strength at an early age was found to be nearly linear. Further, it was shown that specimens cured at 70 °C for 3 days attained almost identical (bending/compressive) strength to those cured at room temperature for 28 days. Additionally, microstructure evaluation of input materials and samples cured under different conditions was performed by means of XRD, FTIR, SEM and mercury intrusion porosimetry (MIP).
Keywords: alkali activation, slag, influence of curing regime, FTIR
Published in DiRROS: 13.09.2023; Views: 236; Downloads: 127
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Izgradnja lizimetrov za preučevanje izpiranja potencionalno nevarnih snovi iz gradbenih proizvodov
Janez Turk, Janko Urbanc, Ana Mladenovič, Alenka Sešek Pavlin, Primož Oprčkal, Karmen Fifer Bizjak, Barbara Likar, Marko Brodnik, Nina Mali, 2020, original scientific article

Abstract: Z uporabo recikliranih odpadkov v gradbeništvu nadomeščamo naravne materiale in s tem vzpostavljamo krožno gospodarstvo na lokalnem nivoju. Pomemben vidik je tudi ohranjanje naravnih virov. To je še posebno pereče pri zemeljskih delih (npr. zasipih in nasipih), kjer prihaja do velike porabe materialov. Geotehnični kompoziti iz recikliranih materialov, v primerjavi z naravnimi agregati ali zemljinami, lahko vsebujejo višje celotne koncentracije potencialno nevarnih snovi (težke kovine, klorid, sulfat, fluorid, organska onesnaževala itd.). Pogoj za uporabo takšnih kompozitov je, da so v njih potencialno nevarne snovi imobilizirane in da so zato iz kemijskega vidika trajno inertni. Možni vplivi na okolje, predvsem prenos različnih potencialno nevarnih snovi iz kompozitov v tla oziroma vodonosnik, so običajno ovrednoteni na laboratorijski ravni, medtem ko je njihovo obnašanje v dejanskem okolju slabo proučeno. Zato se pojavljajo zahteve po razvoju občutljivih, zanesljivih in cenovno ter časovno učinkovitih orodij za določitev masnih tokov potencialno nevarnih snovi iz gradbenih proizvodov, na primer geotehničnih kompozitov, pod vplivi različnih okoljskih dejavnikov. V članku predstavljamo postopek vzpostavitve terenskega laboratorija na osnovi sistema "pan" lizimetrov, za zbiranje izcednih voda iz zasipov, ki so bili izdelani iz geotehničnih kompozitov iz recikliranih materialov. Lizimetre smo konstruirali in izvedli tako, da je njihova izgradnja cenovno ugodna, hkrati pa so po svojih dimenzijah dovolj veliki, da reprezentativno odražajo procese v zgrajenih geotehničnih zasipih. Pridobljeni podatki o količini in parametrih izcedne vode bodo služili kot osnova za določanje vodne bilance in za študij imobilizacije potencialno nevarnih snovi v kompozitih. Hkrati bodo uporabljeni kot vhodni podatki za geokemijski numerični model, s katerim bomo simulirali transport potencialno nevarnih snovi, sproščenih iz preučevanih kompozitov, v različnih tipih vodonosnikov (npr. medzrnski in razpoklinski).
Keywords: lizimeter, izlužek, okoljski monitoring, geotehnični zasip, odpadki
Published in DiRROS: 12.09.2023; Views: 244; Downloads: 110
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