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Pilot production of façade panels : variability of mix design
Majda Pavlin, Barbara Horvat, Vilma Ducman, 2023, objavljeni znanstveni prispevek na konferenci

Povzetek: As part of the WOOL2LOOP project, the Slovenian National Building and Civil Engineering Institute (ZAG), in collaboration with Termit d.d. were responsible for the production of façade panels. An initial mix design was developed at ZAG, where alkali-activated façade panels were produced, primarily from stone wool waste, while production took place at Termit. The mix design was changed twice during the pilot production, before a final product with suitable durability was developed. A compressive strength of up to 60 MPa and bending strength of approximately 20 MPa was achieved. The mechanical properties, however, varied, due to the unevenly milled batches of the milled mineral wool. Milling on a larger scale is very challenging, and it is difficult to obtain consistent quality of the milled material. Once the correct curing process had been found, however, the panels produced showed good performance. Moreover, the results from leaching tests showed that the elevated concentrations of certain elements (Cr, As and Mo) did not exceed the legal limits for non- hazardous waste.
Ključne besede: waste mineral wool, alkali activated material, façade panels, pilot production, circular economy
Objavljeno v DiRROS: 28.11.2023; Ogledov: 24; Prenosov: 6
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Microwave irradiation of alkali - activated metakaolin slurry
Barbara Horvat, Branka Mušič, Majda Pavlin, Vilma Ducman, 2023, objavljeni znanstveni prispevek na konferenci

Povzetek: The building and civil engineering industry generates more than 40% of man-caused carbon emissions, consumes a lot of energy just to produce building materials, generates a large amount of waste through construction and demolition, and consumes a large amount of natural resources. One of the possible solutions is to use alkali-activated materials, which can use waste instead of raw materials and are produced at lower temperatures, with less energy consumption and in less time than traditional building products. All of this lowers the carbon footprint, which could be further reduced by the timely-short implementation of microwave irradiation in the early stages of alkali-activation synthesis. Therefore, metakaolin activated with Na-water glass in a theoretically optimal ratio was irradiated with microwaves of 2.45 GHz at powers of 100 W and 1000 W for 1 min, and compared to non-irradiated reference cured only at room conditions. Samples prepared at higher power, i.e., 1000 W, solidified completely and foamed. TG-DTA was performed on all samples in the early stages of curing, mechanical strengths were measured on 3 and 28-day- old samples, and leaching tests on aged samples.
Ključne besede: metakaolin, alkali activated material, alkali activated foams, microwave irradiation
Objavljeno v DiRROS: 28.11.2023; Ogledov: 25; Prenosov: 7
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Potential of green ceramics waste for alkali activated foams
Barbara 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: 141; Prenosov: 65
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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, 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: 124; Prenosov: 70
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Influence of particle size on compressive strength of alkali activated refractory materials
Barbara 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: 210; Prenosov: 183
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Mechanical, microstructural and mineralogical evaluation of alkali-activated waste glass and stone wool
Majda Pavlin, Barbara Horvat, Ana Frankovič, Vilma Ducman, 2021, izvirni znanstveni članek

Povzetek: Mineral waste wool represents a significant part of construction and demolition waste (CDW) not yet being successfully re-utilized. In the present study, waste stone wool (SW) and glass wool (GW) in the form received, without removing the binder, were evaluated for their potential use in alkali activation technology. It was confirmed that both can be used in the preparation of alkali-activated materials (AAMs), whether cured at room temperature or at an elevated temperature in order to speed up the reaction. The results show that it is possible to obtain a compressive strength of over 50 MPa using SW or GW as a precursor. A strength of 53 MPa was obtained in AAM based on GW after curing for 3 days at 40 °C, while a similar compressive strength (58 MPa) was achieved after curing the GW mixture for 56 days at room temperature. In general, the mechanical properties of samples based on GW are better than those based on SW. The evolution of mechanical properties and recognition of influential parameters were determined by various microstructural analyses, including XRD, SEM, MIP, and FTIR. The type of activator (solely NaOH or a combination of NaOH and sodium silicate), and the SiO2/Na2O and liquid to solid (L/S) ratios were found to be the significant parameters. A lower SiO2/Na2O ratio and low L/S ratio significantly improve the mechanical strength of AAMs made from both types of mineral wool.
Ključne besede: alkali activation, waste mineral wool, mechanical strength
Objavljeno v DiRROS: 31.07.2023; Ogledov: 135; Prenosov: 141
.pdf Celotno besedilo (9,79 MB)
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Influence of microwaves in the early stage of alkali activation on the mechanical strength of alkali-activated materials
Barbara Horvat, Majda Pavlin, Vilma Ducman, 2023, izvirni znanstveni članek

Povzetek: This study focuses on the influence of microwave irradiation dosimetry on alkali-activated slurry in its early stages. The impact on the chemistry and mineralogy along with the mechanical properties were evaluated by changing the power of microwaves and their duration of exposure. This influenced the dissolution of amorphous content, diffusion, and self-assembly into an aluminosilicate network. The precursors used in this study were metakaolin, a non-waste material commonly used in geopolymerisation technology, and local fly ash and ladle furnace slag as secondary materials. Furthermore, they were chemically and mineralogically analysed, and their mixtures with NaOH and Na-water glass provided the optimal ratio of the amount of elements obtained using the pre-calculation approach. However, the potential extra addition of water was experimentally determined to allow complete wetting of the material and solid workability during moulding. Using Fourier-transform infrared spectroscopy, the influence of water was further investigated in alkali-activated slag and fly ash irradiated with microwaves, which resulted in the highest values of mechanical strength in the dosimetry-mapping part of the analysis. In addition to the time dependence of the expected mechanical strength on the ageing of the alkali- activated material, the synthesised material exhibited a significant dependence on the dose of microwave irra- diation, which was different for every precursor as well as every mixture with different chemistries.
Ključne besede: odpadni material, alkalijska aktivacija, obsevanje z mikrovalovi, mehanska trdnost, waste material, alkali activation, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.07.2023; Ogledov: 199; Prenosov: 163
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Preparation of façade panels based on alkali-activated waste mineral wool, their characterization and durability aspects
Majda Pavlin, Barbara Horvat, Vilma Ducman, 2022, izvirni znanstveni članek

Povzetek: Mineral wool is a widely used insulation material and one of the largest components of construction and demolition waste, yet it mainly ends up in landfills. In this work, we explored the potential recycling of waste stone wool in the pilot production of alkali-activated façade panels. The current work shows mechanical properties, SEM-EDS and mercury intrusion porosimetry analyses for three different mix designs used for the preparation of façade panels. They are all composed of waste stone wool and differ in the amount of co-binders (local slag, lime, metakaolin and/or fly ash) selected by the preliminary studies. In this study, co-binders were added to increase early strength and improve the mechanical properties and freeze-thaw resistance. The mechanical properties of each were measured up to 256 days, different durability tests were executed, and, by evaluating the mechanical properties, microstructure and workability of the mortar, the most suitable mix was selected to be used for pilot production. In addition, the leaching test of the selected mixture showed no exceeded toxic trace elements and therefore got classified as non-hazardous waste after its use.
Ključne besede: alkali activation, waste mineral wool, SEM, XRF, XRD, mechanical strength
Objavljeno v DiRROS: 19.06.2023; Ogledov: 180; Prenosov: 78
.pdf Celotno besedilo (1,27 MB)
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The preparation and characterization of low-temperature foams based on the alkali activation of waste stone wool
Majda Pavlin, Barbara Horvat, Mark Češnovar, Vilma Ducman, 2022, izvirni znanstveni članek

Povzetek: Waste mineral wool represents a huge amount of construction and demolition waste that is still not adequately returned into the value chain but needs to be landfilled. In the present study, waste stone wool (SW) was evaluated for the preparation of alkali-activated foams. For this purpose SW was milled and sieved below 63 μm, then the activator (sodium silicate) and different amounts of foaming agent (hydrogen peroxide, H2O2), varying between 1 wt% and 3 wt%, were added to the slurry and cured in moulds at an elevated temperature (70 ◦ C) for three days. In this way, foamed, highly porous materials were obtained whose density and mechanical properties were influenced by the amount of foaming agent used. The densities obtained ranged between 1.4 and 0.5 g/cm3, with corresponding mechanical properties of between 12.6 and 1.5 MPa and total porosities in the range 37.8–78.6%, respectively. In the most porous samples with the total porosity of 78.6%, a thermal conductivity of 0.092 W/(m∙K) was confirmed. The study confirmed the suitability of waste mineral wool (in our case SW) as a precursor for alkali-activated foams with potential use in the construction sector or other industrial applications.
Ključne besede: alkali activation, waste mineral wool, mechanical strength, open access, alkalijska aktivacija, odpadna volna, SEM, XRF, XRD, mehanska trdnost, odprti dostop
Objavljeno v DiRROS: 19.06.2023; Ogledov: 163; Prenosov: 125
.pdf Celotno besedilo (9,47 MB)
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Clay rich river sediments calcined into precursors for alkali activated materials
Lea Žibret, Wolfgang Wisniewski, Barbara Horvat, Mojca Božič, Boštjan Gregorc, Vilma Ducman, 2023, izvirni znanstveni članek

Povzetek: Alkali activated materials (AAMs), a potential alternative to cement-based products or ceramics, can incorporate large amounts of currently landfilled aluminosilicate rich materials such as calcined clay-rich river sediments collected at hydropower plant dams. Untreated fresh sediment and untreated aged sediment intended to serve as AAM precursors were calcined to increase their amorphous content, then activated by Na or K-based silicate or hydroxide solutions and cured at 60 ◦C for three days. Up to 30 mass % (ma%) of fly ash (FA) or ladle slag (LS) increased the mechanical performance. The phase composition and microstructure are analyzed using X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and mercury intrusion porosimetry to gain further insight into how the additives influence the final properties of the resulting AAMs. The main crystalline components of the prepared AAMs are quartz, illite/muscovite and feldspar. The amorphous content reaches up to 52.5 ma% in the Na-activated AAMs and up to 48.8 ma% in K-activated AAMs. The acquired results confirm the suitability of the investigated sediments as sole precursors for AAMs. The mechanical properties of the AAMs can be improved by adding FA and/or LS.
Ključne besede: sediments, alkali activated materials, properties
Objavljeno v DiRROS: 30.05.2023; Ogledov: 153; Prenosov: 152
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