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: 46; Prenosov: 66
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2. Influence of test methodology on the characterization of the parallel-to-grain timber embedment strength and foundation modulus of dowelsCaroline D. Aquino, Rodrigues Leonardo G., Michael Schweigler, Meta Kržan, Zheng Li, Jorge M. Branco, 2024, izvirni znanstveni članek Povzetek: A reliable determination of the embedment strength and foundation modulus of timber elements is critical for the design and safety assessment of joints in timber structures. However, the existence of various test configurations for characterising the embedding properties of large diameter steel fasteners in timber elements poses challenges in directly comparing and utilising available test data. This paper aims to provide an insight into the influence of embedment property test methods, comparing experimental results from different test setups within the guidelines of the EN 383 and ASTM D 5764-97a standards for European softwood species, Scots pine wood (Pinus sylvestris) and Norway spruce (Picea abies). In addition to the test guidelines, the thickness of the specimen and the application of the load was evaluated within the protocols. A comprehensive statistical analysis was performed to identify statistically significant differences between the groups evaluated. The results of the analysis revealed disagreement between the standards in the evaluation of the strength of the embedding, highlighting the potential bias inserted by the experimental setup and protocol. Furthermore, it was proven that the thickness of the specimens influences both the embedding strength and the foundation modulus of the wood species tested. Finally, no distinctions were observed between tensile and compressive loading within the guidelines of the EN 383 standard. Ključne besede: embedment strength, foundation modulus, dowel-type connections, test methods Objavljeno v DiRROS: 15.04.2024; Ogledov: 289; Prenosov: 146
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3. Green transition in slovenian building and civil engineering industry : 10 years of research on alkali-activated materials and alkali-activated foamsBarbara Horvat, Branka Mušič, 2024, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje) Povzetek: The building and civil engineering industry yearly causes more than 40% of man-made CO2 and consumes raw materials for two-thirds of Mont Everest. To decrease the carbon footprint and consumption of raw materials, alkali-activated materials (AAMs) are researched as an alternative to conventional building and civil engineering products like cements, mortar, and ceramics. Ideally, locally available waste materials are used as ingredients: (i) as precursors that react with alkali and form an aluminosilicate network, and (ii) as fillers that get permanently encapsulated and safely stored in AAMs. The addition of gas bubbles and lightweight fillers transforms AAMs into alkali-activated foams and alkali-activated lightweight materials that have the potential to be used as thermal and acoustic insulation materials. Although AAMs are researched worldwide, this review focuses on the state-of-the-art localised solely to Slovenia, particularly on the materials and curing procedures used, as well as on the scientific contribution of the basic research. Besides, the year 2024 marks 10 years of research on alkali activation of raw and waste inorganic materials in Slovenia. Ključne besede: secondary raw material, alkali-activated material, alkali-activated foams, alkali, circular economy, microwave irradiation, mechanical strength Objavljeno v DiRROS: 12.03.2024; Ogledov: 341; Prenosov: 292
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4. Influence of ammonium polyphosphates and 2,4,6-triamino-1,3,5-triazine on the mechanical-physical properties of polyurethane and alkali-activated materialsBranka Mušič, Barbara Horvat, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: In building constructions, the tendency towards an ever-better material directs us to composite materials. In this work, we prepared an organic-organic and organic-inorganic composite material by incorporating fire retardants, ammonium polyphosphates, and 2,4,6-triamino-1,3,5-triazine, into a polyurethane network and an aluminosilicate network (ASN) of alkali-activated material. Polyurethane foams (PUR) are well-known materials that, due to their properties, such as low weight-to-strength ratio, low electrical and thermal conductivity, flexibility, and relatively simple preparation process, are used in various industries, also in the construction industry, e.g., for thermal insulation of windows and doors or fixing and sealing joinery. Opposite, the ASN of alkali-activated metakaolin, successfully paves the way for new applications, such as high-temperature protection. In this paper, these interactive properties of prepared composites are studied using thermal testing and mechanical analysis. It was found that inhibitors significantly increase the fire resistance of PUR systems while they slightly reduce the mechanical properties. Incorporating polymer flame retardant into ASN in building products, such as façade panels , can decrease the mechanical properties but can offer the non-flammable building envelope not get heated from burning surroundings, i.e., not becoming a convection heat source, but rather represent a fire-distinguisher for flammable materials. Ključne besede: flame retardants, polyurethane, alkali activated material, metakaolin, microwave irradiation, mechanical strength Objavljeno v DiRROS: 12.03.2024; Ogledov: 442; Prenosov: 386
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5. Waste rubber incorporated in the alkali-activated metakaolin’s aluminosilicate network enhanced by microwave irradiationBarbara Horvat, Branka Mušič, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Building materials represent the possibility of prolonging the life of waste materials. The key is to ensure that the products are suitable for their function. So we activated metakaolin with the alkaline Na-silicate solution in the ratio that ensures the prevention of efflorescence and high mechanical strength (Horvat and Ducman, 2019). As the waste material (to be incorporated in the aluminosilicate network (ASN) of the alkali-activated metakaolin) ground waste rubber from electric cables was used in the preselected mass ratios. Its inclusion in products, like paving stones, can reduce stiffness, improve durability, dampen vibrations, and reduce road noise. The mechanical strengths of test samples with rubber present on the active surface or slightly below were higher compared to samples where rubber was encapsulated throughout the volume. Compressive strength was higher when samples were irradiated with low powers of microwaves while irradiation with higher powers led to the foaming of alkali-activated slurry. The encapsulation quality of the ground rubber was evaluated by SEM while the chemical influence on ASN was determined by EDS, FTIR, and XRD. Slipperiness change on the active surface of pavement stones proved that the addition of the ground rubber enhanced the walking safety of the product. Ključne besede: secondary raw material, alkali activated material, waste rubber, metakaolin, encapsulation of organic in inorganic material, microwave irradiation, mechanical strength Objavljeno v DiRROS: 12.03.2024; Ogledov: 590; Prenosov: 453
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6. Thermal insulation and flammability of composite waste polyurethane foam encapsulated in geopolymer for sustainable building envelopeBarbara Horvat, Nataša Knez, Uroš Hribar, Jakob Koenig, Branka Mušič, 2024, izvirni znanstveni članek Povzetek: Polyurethane foam (PUR) is a lightweight, thermally insulating, widely used, and highly flammable material that has after its use an adverse effect on the environment, i.e., PUR disposal is considered hazardous. Its flammability can be mitigated using various fire retardants, but they do not change the hazardous nature of waste PUR. Therefore, in the current study, waste PUR with and without flame retardants based on N and P was incorporated into a geopolymer, the alkali-activated material (AAM) based solely on metakaolin, to evaluate the potential recycling route of waste PUR while taking into account its flammability, so it can enter safely into the circular economy through the building industry. To enhance the mechanical properties of the composite, a fresh mixture was irradiated with microwaves. However, the irradiation of geopolymer containing PUR negatively influenced mechanical performance, which led to the evaluation of the behaviour of the complex dielectric constant of PUR and fire retardants. Materials and composites were evaluated regarding their chemistry, mineralogy, microstructure, and porosity to connect the structure with extrinsic properties like geometrical density, thermal conductivity, and fire properties. Nonetheless, positive influences of PUR being encapsulated in the geopolymer were lowered density (from 1.8 to 1.6 kg/l) and improved thermal insulation ability (from 940 to 860 mW/(m·K)) of the composites: with the inclusion of <5 % of PUR, thermal insulation improved by nearly 10 %. However, the contribution of PUR to the composite originated from its skeleton, which has more than 15 times bigger geometrical density (0.81 kg/l) compared to the density of the skeleton (0.047 kg/l). This offers an open field for further advancements of thermal properties, but would also lead to a decrease of the compressive strength, which was already lowered from 90 MPa for 30 % with <5 % of added grated PUR. Furthermore, the flammable nature of PUR and its other drawbacks can be controlled by permanent embedding in the noncombustible structure of geopolymer, making the envelope of sustainable buildings green and safer. Overall, including grated waste PUR in geopolymer represents a promising, easy, cost-effective recycling path with low energy consumption, where the composite cannot develop fire on a scale of pure PUR, even in the worst-case scenario, but only if the composite is designed in a way, that flammable materials cannot join flames during their combustion. This paper gives prospects to other flammable waste materials to be safely used in the circular economy, and to porous materials to shape properties of the composite by their intrinsic and/or extrinsic properties. Ključne besede: waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength Objavljeno v DiRROS: 01.03.2024; Ogledov: 696; Prenosov: 759
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7. 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: 280
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8. 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: 435; Prenosov: 488
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9. PUR in geopolymerBarbara Horvat, Nataša Knez, Uroš Hribar, Jakob Koenig, Branka Mušič, 2024, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: The dataset supports the results shown in the tables and figures in the article entitled “Thermal insulation and flammability of composite waste polyurethane foam encapsulated in geopolymer for sustainable building envelope” (doi: 10.1016/j.jclepro.2024.141387). It contains measurements of fire-behaviour characteristics, thermal conductivity, the behaviour of the material in the electromagnetic field in relation to the frequency, mechanical and structural evaluation, as well as chemical and mineralogical analysis. Ključne besede: measurements, waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength Objavljeno v DiRROS: 20.02.2024; Ogledov: 507; Prenosov: 236
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10. Ultra-high strenght TWIP steel with high chromium contentPavel Podaný, Tomáš Studecký, Tomas Gregor, Radek Prochazka, Aleksandra Kocijan, 2023, izvirni znanstveni članek Povzetek: A new ultra-high strength steel with a fully austenitic microstructure and twinning-induced plasticity (TWIP) effect has been developed. TWIP effect gives this steel a good combination of high strength of over 1000 MPa and ductility of over 35%. This new steel has a high chromium content, which increases its corrosion resistance. By combining cold rolling and annealing, the steel has achieved a very fine austenitic microstructure with an average grain diameter of 2.85 µm. This steel could be used for structural applications or components that need to withstand high levels of stress, deformation and corrosion environment. Ključne besede: TWIP steels, corrosion resistance, microstructure, tensile strength, plasticity Objavljeno v DiRROS: 31.01.2024; Ogledov: 408; Prenosov: 231
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