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2. Mineral waste into alkali-activated pavementsMajda Pavlin, Kaja Zupančič, Alenka Sešek Pavlin, 2025, objavljeni znanstveni prispevek na konferenci Povzetek: The study highlights the pressing need to recycle mineral waste to mitigate resource depletion and environmental damage. It focuses on creating sustainable pavement slabs through alkali activation, using a variety of waste materials such as bio-ash, local slags and mineral wool. Through extensive testing of different mix designs, the optimal mixture was identified: bio-ash, ladle slag, and metakaolin, activated with sodium silicate. This combination demonstrated good mechanical properties and showed low concentrations of toxic elements in leaching tests, confirming environmental safety. The research also prioritized energy efficiency, with the curing process conducted at room temperature and demolding after just one day. A test field at Termit d.d. was established to assess the practical application and potential for commercial use of these innovative paving materials, aiming to support a circular economy by extending the lifecycle of resources.
Ključne besede: alkali-activation, pavement slabs, mineral waste, recycling
Objavljeno v DiRROS: 07.04.2025; Ogledov: 109; Prenosov: 46
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3. Influence of curing / drying methods including microwave heating on alkali activation of waste casting coresBarbara Horvat, Vilma Ducman, 2021, objavljeni znanstveni prispevek na konferenci Povzetek: Within previous investigation alkali activation of waste casting cores at room temperature did not give promising results, i.e. when the precursor was gently ground and sieved below 600 %m the alkali activated material fell apart at demolding, and when the precursor was ground below 90 %m, the alkali activated material did not solidify in more than 2 years. , Therefore different drying/curing methods were applied to enhance the reaction. Waste casting cores were prepared in two granulations (sieved below 600 %m and below 90 %m), activated with Na -water glass and 10 M NaOH, cured at different temperatures (70 °C and room temperature), and subsequently cured/dried at three different conditions: room temperature, 110 °C, and irradiated with microwaves. The highest compressive strength, 25 MPa, was gained with subsequent curing/drying at 110 °C. The lowest density, 0.5 kg/l, with compressive strength above 3 MPa, was achieved with subsequent curing/drying with microwaves .
Ključne besede: waste casting cores, alkali activation, curing, drying, microwaves, mechanical strength
Objavljeno v DiRROS: 22.01.2024; Ogledov: 701; Prenosov: 476
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4. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Ključne besede: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Objavljeno v DiRROS: 22.11.2023; Ogledov: 1746; Prenosov: 428
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5. Production of lightweight alkali activated mortars using mineral woolsAhmad Alzaza, Mohammad Mastali, Paivo Kinnunen, Lidija Korat Bensa, Zahra Abdollahnejad, Vilma Ducman, Mirja Illikainen, 2019, izvirni znanstveni članek Povzetek: This experimental study aimed to develop a fiber-reinforced lightweight mineral wool-based alkali activated mortar. The lightweight mineral wool-based alkali activated mortars were produced using premade foam and reinforced by polypropylene (PP) fibers. They were assessed in terms of fresh and hardened-state properties. Fresh-state properties were investigated by mini-slump tests. Hardened-state characteristics were assessed by ultrasonic pulse velocity, dry density, compressive and flexural strengths, drying shrinkage, efflorescence, water absorption, and permeable porosity. For the first time, the resistance of the synthesized lightweight mineral wool-based alkali activated mortars against harsh conditions (carbonation, freeze and thaw, and high temperature) were evaluated. The porous structures of the developed lightweight alkali activated mortars were also analyzed using an X-ray micro-computed tomography (CT) technique. Lightweight mix compositions with densities in a range of 770%1510 kg/m3, compressive strengths of 1%9 MPa, and flexural strengths of 2.6%8 MPa were developed. Increases in both density and strength after carbonation were also recorded, while a decrease of strength was noticed after exposure to freeze/thaw and high temperatures of up to 500 %C.
Ključne besede: alkali activation, mineral wool, mortars
Objavljeno v DiRROS: 24.10.2023; Ogledov: 868; Prenosov: 429
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6. Impacts of casting scales and harsh conditions on the thermal, acoustic, and mechanical properties of indoor acoustic panels made with fiber-reinforced alkali-activated slag foam concretesMohammad Mastali, Paivo Kinnunen, Marjaana Karhu, Zahra Abdollahnejad, Lidija Korat Bensa, Vilma Ducman, Ahmad Alzaza, Mirja Illikainen, 2019, izvirni znanstveni članek Povzetek: This paper presents experimental results regarding the efficiency of using acoustic panels made with fiber-reinforced alkali-activated slag foam concrete containing lightweight recycled aggregates produced by using Petrit-T (tunnel kiln slag). In the first stage, 72 acoustic panels with dimension 500 % 500 % 35 mm were cast and prepared. The mechanical properties of the panels were then assessed in terms of their compressive and flexural strengths. Moreover, the durability properties of acoustic panels were studied using harsh conditions (freeze/thaw and carbonation tests). The efficiency of the lightweight panels was also assessed in terms of thermal properties. In the second stage, 50 acoustic panels were used to cover the floor area in a reverberation room. The acoustic absorption in diffuse field conditions was measured, and the interrupted random noise source method was used to record the sound pressure decay rate over time. Moreover, the acoustic properties of the panels were separately assessed by impedance tubes and airflow resistivity measurements. The recorded results from these two sound absorption evaluations were compared. Additionally, a comparative study was presented on the results of impedance tube measurements to compare the influence of casting volumes (large and small scales) on the sound absorption of the acoustic panels. In the last stage, a comparative study was implemented to clarify the effects of harsh conditions on the sound absorption of the acoustic panels. The results showed that casting scale had great impacts on the mechanical and physical properties. Additionally, it was revealed that harsh conditions improved the sound properties of acoustic panels due to their effects on the porous structure of materials.
Ključne besede: alkali activation, slag, acoustic panels
Objavljeno v DiRROS: 15.09.2023; Ogledov: 811; Prenosov: 451
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7. Potential of green ceramics waste for alkali activated foamsBarbara Horvat, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: 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.
Ključne besede: alkali activation, foaming, SEM, XRF, XRD, mechanical strength
Objavljeno v DiRROS: 14.09.2023; Ogledov: 1693; Prenosov: 456
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8. Aggregates obtained by alkali activation of fly ash : the effect of granulation, pelletization methods and curing regimesOgnjen 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: 765; Prenosov: 431
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9. The potential of ladle slag and electric arc furnace slag use in synthesizing alkali activated materials; the influence of curing on mechanical propertiesMark 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: 797; Prenosov: 417
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10. Influence of particle size on compressive strength of alkali activated refractory materialsBarbara Horvat, Vilma Ducman, 2020, izvirni znanstveni članek Povzetek: Influence of particle size on the mechanical strength of alkali activated material from waste refractory monolithic was investigated in this study. Precursor was chemically and mineralogically analysed, separated on 4 fractions and alkali activated with Na-water glass. Alkali activated materials were thoroughly investigated under SEM and XRD to evaluate the not predicted differences in mechanical strength. Influence of curing temperature and time dependence at curing temperatures on mechanical strength were investigated in the sample prepared from a fraction that caused the highest compressive strength.
Ključne besede: refractory materials, alkali activation, particle size, SEM, XRF, XRD, compressive strength
Objavljeno v DiRROS: 21.08.2023; Ogledov: 1148; Prenosov: 592
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