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1.
Aggregates obtained by alkali activation of fly ash : the effect of granulation, pelletization methods and curing regimes
Ognjen Lj. Rudić, Vilma Ducman, Mirjana Malešev, Vlastimir Radonjanin, Suzana Draganić, Slobodan Šupić, Miroslava Radeka, 2019, izvirni znanstveni članek

Povzetek: This paper presents results regarding the phase composition, microstructure and textural properties of two types of aggregates, which were prepared via crushing or pelletization of alkali-activated Class F fly ash and cured under different conditions. The alkali activator was the same for aggregate products, containing an alkaline solution consisting of 8 M NaOH and Na-silicate (8 M NaOH/Na-silicate = 1:2.5 mass ratio). The aforementioned properties were influenced by two different preparation procedures combined with varying curing regimes (under normal conditions at 20 %C, RH 40%60% for 28 and 120 days and under an accelerated regime, at 65 %C for 5 days). Aggregates were characterized using X-ray diffraction (XRD), Fourier-transform transmission infrared spectroscopy (FTIR), back scattered electron microscopy with energy dispersive spectrometer (BSE-EDS) analyses and mercury intrusion porosimetry (MIP). The results showed noteworthy structural and textural diversities between the two types of aggregate. The method of preparation and curing regime affected the formation of the N-A-S-H structure and the texture of the alkali-activated fly ash product, with the crushing method giving an advantage
Ključne besede: alkali activation, agregat, FTIR
Objavljeno v DiRROS: 14.09.2023; Ogledov: 214; Prenosov: 124
.pdf Celotno besedilo (5,27 MB)
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2.
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, izvirni znanstveni članek

Povzetek: 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).
Ključne besede: alkali activation, slag, influence of curing regime, FTIR
Objavljeno v DiRROS: 13.09.2023; Ogledov: 235; Prenosov: 127
.pdf Celotno besedilo (10,76 MB)
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3.
An electrochemical and spectroscopic study of surfaces on bronze sculptures exposed to urban environment
Dajana Mikić, Helena Otmačić Ćurković, Tadeja Kosec, Neven Peko, 2021, izvirni znanstveni članek

Povzetek: Polluted urban environment enhances dissolution of patina and underlying bronze material of recent and historical bronze sculptures exposed outdoors. In this work, two bronze statues, situated in one of the most polluted Croatian cities, were examined in order to characterize composition of patina and its electrochemical stability. The composition of patina on several positions on each sculpture was determined by EDS, Raman spectroscopy, and FTIR measurements. Electrochemical impedance spectroscopy measurements were conducted in order to evaluate the corrosion stability of both patina and underlying bronze. Results obtained in this work show that the two examined bronze sculptures were covered with patina layer that was mainly composed of copper sulfides and sulphates, which is in accordance with the high concentrations of H2S and SO2 in the atmosphere. However, the variations in the appearance of FTIR and Raman spectra revealed that the amount of each species differed from spot to spot, as well as the fact that other compounds, such as carbonates, were present at some areas. This difference in patina composition was reflected in electrochemical behavior as observed by electrochemical impedance spectroscopy.
Ključne besede: bronze, corrosion, spectroscopy, FTIR, Raman, EIS, open access
Objavljeno v DiRROS: 16.05.2023; Ogledov: 274; Prenosov: 159
.pdf Celotno besedilo (4,82 MB)
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Etanolamin v zaščitenem lesu
Miha Humar, Marko Petrič, 2000, izvirni znanstveni članek

Povzetek: Zaščita lesa je, kljub poostrenim okoljevarstvenim zahtevam, še vedno nujno potrebna in ekonomsko upravičena. Zaradi dobrih fungicidnih lastnosti se za impregnacijo lesa množično uporablja tudi bakrove spojine. Ker se dokaj slabo vežejo v les, se iz njega izpirajo. V kombinaciji s kromom pa se baker v lesu dobro fiksira. V zadnjem času so v mnogih državah omejili uporabo kromovih soli, oziroma jih nameravajo prepovedati. Strokovnjaki zato za fiksacijo bakra iščejo druge spojine. Kot primerni in potencialno uporabni so se izkazaliamini. Raziskovali smo interakcije med bakrovimi pripravki z etanolaminom (C2H7NO, 2-aminoetanol) in komponentami lesa. Opazili smo, da etanolamin z lesom reagira. Z metodo nihajne spektroskopije (FTIR) smo opazilispremembe na skupinah lignina in polioz. Razvili smo tudi metodo, kjer reagent z barvno reakcijo dokaže prisotnost etanolamina v lesu.
Ključne besede: zaščita lesaq, etanolamin, fiksacija etanolamina, barvna reakcija, FTIR, zaščiteni les
Objavljeno v DiRROS: 12.07.2017; Ogledov: 4313; Prenosov: 1817
.pdf Celotno besedilo (748,24 KB)

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