1. Lightweight aggregates made from fly ash using the cold-bond process and their use in lightweight concreteAna Frankovič, Violeta Bokan-Bosiljkov, Vilma Ducman, 2017, izvirni znanstveni članek Povzetek: Aggregates made from fly ash have been developed by means of the cold-bonding process, with the addition of Portland cement as a binder at (10, 20, and 30) % of mass fractions, and by pouring the mixtures into moulds. After curing for 28 d the samples were processed into aggregate by crushing and sieving. An aggregate containing a weight percentage of 10 % of cement was additionally produced by pelletization on a granulating plate. The density, water-adsorption capacity, porosity, compressive strengths, and frost resistance of the samples were determined. The aggregates prepared by both routes were then used to make concrete samples, whose properties were then compared to those of conventional concrete made using limestone aggregate. The compressive strength of the concrete made with the granulated aggregate reached 16.0 MPa after 28 d, whereas that of the concrete made with crushed aggregate amounted to 24.1 MPa, and that of the conventional concrete was 34.6 MPa. Ključne besede: fly ash, lightweight aggregates, density, compressive strength, frost resistance Objavljeno v DiRROS: 14.08.2024; Ogledov: 53; Prenosov: 69
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2. An evaluation of marine sediments in terms of their usability in the brick industry : case study Port of KoperPatrik Baksa, Franka Cepak, Rebeka Kovačič Lukman, Vilma Ducman, 2018, izvirni znanstveni članek Povzetek: A dredging process is essential for the development of harbours and ports, allowing the functional daily operation of the port. The management of dredged material represents a worldwide challenge, especially considering unwanted deposition of material. Because of their chemical, petrographic, mineralogical and homogeneity composition, marine sediments could represent an appropriate raw material for the brick industry, particularly for the production of clay blocks, roofing and ceramic tiles. In this study dredged material from Port of Koper was tested for such use, thus various analyses were carried out in order to determine if the dredged material is environmentally friendly and suitable for use in the brick industry. These included: chemical analysis, mineralogical analysis, particle size analysis, chloride content analysis and tests of firing in a gradient furnace. Furthermore, tests of mechanical properties, as well as tests of the frost-resistance of the samples were carried out. On the basis of the primary analyses and samples prepared in a laboratory, it was confirmed that marine sediments from the Port of Koper, without any additives are only conditionally suitable as a source material for producing brick products, because without additives they exhibit too much shrinkage on drying and firing, as well as high water absorption, this can be improved by the incorporation of suitable additives, for example, virgin clay or other suitable waste material. The approach described herewith can also be followed to assess sediments from other ports and rivers regarding its potential use in clay brick sector. Ključne besede: dredge marine sediment, recycling, clay bricks, mechanical properties, chemical analysis Objavljeno v DiRROS: 14.08.2024; Ogledov: 51; Prenosov: 27
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3. Increasing the amorphous content in river sediments intended for supplementary cementitious materials using flame synthesisWolfgang Wisniewski, Jozef Kraxner, Lea Žibret, Dušan Galusek, Vilma Ducman, 2024, izvirni znanstveni članek Povzetek: Dredged river sediments are currently a waste material which is mainly landfilled or reintegrated into rivers. They can also be used as a renewable resource for the construction sector. Pre- treatments at high temperatures allow their use for more advanced applications such as supplementary cementitious materials (SCMs) or as a precursor for alkali activated materials (AAMs). The work presented here shows that flame synthesis can be used to almost completely vitrify such sediments and increase their leachability for Al and Si beyond the levels achieved by conventional calcination at 750–950 ◦C for 1h.
The reactivity of the prepared samples was analyzed via the Si and Al solubility in 10 M NaOH and was generally increased by the applied treatments but maximized by flame synthesis. Their microstructure was analyzed using scanning electron microscopy and their phase composition was monitored using X-ray diffraction. The results show an almost complete amorphization of the sediments by flame synthesis, however their reactivity does not increase at the same rate. Ključne besede: sediments, SCM, vitrification, properties Objavljeno v DiRROS: 23.05.2024; Ogledov: 287; Prenosov: 251
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4. Why geopolymers and alkali-activated materials are key components of a sustainable world : a perspective contributionWaltraud M. Kriven, Cristina Leonelli, John L. Provis, Aldo R. Boccaccini, Cyril Attwell, Vilma Ducman, Claudio Ferone, Sylvie Rossignol, Tero Luukkonen, Jannie S. J. Van Deventer, José V. Emiliano, Jérôme E. Lombardi, 2024, izvirni znanstveni članek Povzetek: This perspective article delves into the transformative potential of alkali-activated materials, acid-activated materials, and geopolymers in mitigating climate change and market challenges. To harness the benefits of these materials, a comprehensive strategy is proposed. This strategy aims to integrate these materials into existing construction regulations, facilitate certification, and promote market access. Emphasizing research and innovation, the article advocates for, increased funding to refine the chemistry and production of these materials, prioritizing low-cost alternatives and local waste materials. Collaboration between academia and industry is encouraged to expedite technological advances and broaden applications. This article also underscores the need to develop economic and business models emphasizing the long-term benefits of these materials, including lower life-cycle costs and reduced environmental impact. Incentivizing adoption through financial mechanisms like tax credits and subsidies is suggested. The strategy also includes scaling up production technology, fostering industrial collaboration for commercial viability, and developing global supply chains. Educational programs for professionals and regulators are recommended to enhance awareness and adoption. Additionally, comprehensive life-cycle assessments are proposed to demonstrate environmental benefits. The strategy culminates in expanding the applications of these materials beyond construction, fostering international collaboration for knowledge sharing, and thus positioning these materials as essential for sustainable construction and climate change mitigation. Ključne besede: geopolymers, alkali activated materials, perspective Objavljeno v DiRROS: 15.04.2024; Ogledov: 331; Prenosov: 361
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5. Characterization and Mechanical Properties of Sintered Clay MineralsSara Tominc, Vilma Ducman, Jakob Koenig, Srečo D. Škapin, Matjaž Spreitzer, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: The need to reduce energy consumption and the carbon footprint generated by firing ceramics has stimulated research to develop sintering processes carried out at lower temperatures(ideally not above 300 °C) and high pressures (up to 600 MPa), the so-called cold sintering process (CSP) (Grasso et al., 2020, Maria et al., 2017). To evaluate the applicability of CSP to clays, we focused on two representative clay minerals, kaolinite and illite, and on the natural clay material obtained from a Slovenian brick manufacturer. The selected clay materials were characterized on the basis of mineralogical-chemical composition (XRD, XRF) and particle size distribution (SEM analysis, PSD, BET). The powders of clay minerals and natural clay material were first sintered in a heating microscope to determine the sintering conditions and then in a laboratory furnace at 1100 °C for 2 hours and additionally at 1300 °C for kaolinites. The effect of compression of the initial powders on their final properties was also investigated. Ključne besede: conventional sintering, cold sintering, clay minerals, characterization, mechanical properties Objavljeno v DiRROS: 29.03.2024; Ogledov: 351; Prenosov: 160
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6. Innovative pre-fabricated components including different waste construction materials reducing building energy and minimising environmental impacts (InnoWEE)Elena Loredana Fodor, Vilma Ducman, Giovanni Ferrarini, Sergio Tamburini, Constantinos Tsoutis, Francesca Becherini, Antonio Garrido-Marijuán,, Giulia Mezzasalma, Leonardo Rossi, Emil Lezak, Adriana Bernardi, 2019, objavljeni znanstveni prispevek na konferenci Povzetek: InnoWEE is a four-year project (from 2016 to 2020) financed by the European Community that involves ten partners from different European countries, as Greece, Italy, Belgium, Romania, Slovenia, Spain and Poland. The aim is to use the waste materials coming from construction and demolition processes of buildings and include them into a geopolymeric matrix with the purpose of producing prefabricated panels for different applications. Construction and demolition waste (CDW) materials with suitable characteristics have been selected to develop high performance geopolymeric panels for building walls envelopes and radiant panels for indoor walls and ceilings with low environmental impact. Field tests will be carried out in different sites in Europe characterized by different climatic conditions to check the simplicity of the installation procedure and the performance of the panels in terms of energy efficiency and environmental impact. Ključne besede: prefabriced elements, geopolymers, CDW Objavljeno v DiRROS: 08.03.2024; Ogledov: 325; Prenosov: 163
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7. Evaluation of fly ash-based alkali activated foams at room and elevated temperaturesKatja Traven, Mark Češnovar, Srečo D. Škapin, Vilma Ducman, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: Alkali activated materials (AAM) are, in their broadest classification, any binder systems derived by the reaction of an alkali metal source (silicates, alkali hydroxides, carbonates , sulphates) with a solid, amorphous alumosilicate powder (found in precursors such as slag, fly ash and bottom ash). A wide variety of products can be obtained by the alkali activation process and could replace traditional construction products. Among the se, alkali activated foams (AAF) represent one of the most promising materials, owing to their economically accessible alumosilicate rich source materials, including industrial waste materials, clean processing, higher added value and most importantly, pro ducts with competitive properties. In the present study, the properties of alkali activated fly ash - based foam materials were studied at room temperature as well as at elevated temperatures (up to 1200 °C ) in order to develop a durable material in terms o f mechanical properties and suitability for high temperature applications. Ključne besede: lightweight porous insulating material, alkali activated materials, microstructural analysis Objavljeno v DiRROS: 05.03.2024; Ogledov: 429; Prenosov: 363
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8. Foundry wastes as a potential precursor in alkali activation technologyBarbara Horvat, Alenka Sešek Pavlin, Vilma Ducman, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: In this study the amount of amorphous phase of elements useful in alkali activation of waste materials produced by the foundry industry was determined. Waste foundry sands, foundry flue gas and waste casting cores were alkali activated, and waste green ceramics and bottom ash were added to one of the foundry sand samples to shorten the time for producing measurable compressive strength from 1.5 years to 1 week. Ključne besede: alkali activated materials, foundry wastes, compressive strength, upcycling, circular ecnomy Objavljeno v DiRROS: 01.03.2024; Ogledov: 330; Prenosov: 281
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9. The deformation of alkali-activated materials at different curing temperaturesMark Češnovar, Katja Traven, Vilma Ducman, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: Alkali activation is a chemical process whereby materials rich in aluminosilicate, which dissolves in basic media at room temperature, form binding phases by polycondensation. The alkali- activated materials (AAM) are a promising alternative to binding materials such as cement or other products in civil engineering (van Deventer et al., 2012). This study investigates the early age shrinkage behavior of Slovenian ladle and electric arc furnace slag - based alkali activated materials at different curing temperatures. The dimensions of specimens cured at room temperature and elevated temperatures up to 90 °C were measured over the first 7 hours (every 10 min). The results show that the most shrinkage occurred at the highest temperature, owing to the highest rate of evaporation of liquid content. Loss of mass follows from the drying shrinkage. Ključne besede: alkali activated materials, shrinkage, compressive strength Objavljeno v DiRROS: 01.03.2024; Ogledov: 436; Prenosov: 489
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10. The influence of different fibres quantity on mechanical and microstructural properties of alkali-activated foamsKatja Traven, Mark Češnovar, Barbara Horvat, Vilma Ducman, 2022, objavljeni znanstveni prispevek na konferenci Povzetek: Alkali activated foams (AAFs) were produced using electric arc furnace steel slag (EAF) and ladle furnace basic slag (LS), obtained from two metallurgical companies in Slovenia. They were activated with a mixture of sodium water glass (Na2SiO3) and solid NaOH and foamed with hydrogen peroxide (H2O2). Pores were stabilized with the addition of Triton as a surfactant. Four types of fibres were added to the studied mixture (polypropylene (PP), polyvinyl-alcohol (PVA), basalt (B), and glass wool (GW)) in five different quantities: 0.5, 1.0, 1.25, 1.5 and 2.0 vol % in order to additionally stabilize the structure and thus improve its mechanical properties. The results of mechanical properties showed, that compressive strength was increased in all 20 specimens, partially due to the increased density as well as to the fibre addition. Flexural strength on the other hand was the most improved in the samples where PP and PVA fibres were added. The samples with the addition of B and GW fibres on the other hand showed only small or no improvement in flexural strength in comparison to the referenced sample. Additionally, the microstructure of used fibres and selected foams was also investigated by the means of SEM analysis. Ključne besede: fibers, alkali activated foams, properties Objavljeno v DiRROS: 31.01.2024; Ogledov: 323; Prenosov: 168
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