1. 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, published scientific conference contribution (invited lecture) Abstract: 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.
Keywords: secondary raw material, alkali-activated material, alkali-activated foams, alkali, circular economy, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 108; Downloads: 104
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2. The influence of different fibres quantity on mechanical and microstructural properties of alkali-activated foamsKatja Traven, Mark Češnovar, Barbara Horvat, Vilma Ducman, 2022, published scientific conference contribution Abstract: 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.
Keywords: fibers, alkali activated foams, properties
Published in DiRROS: 31.01.2024; Views: 150; Downloads: 63
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3. Microwave irradiation of alkali - activated metakaolin slurryBarbara Horvat, Branka Mušič, Majda Pavlin, Vilma Ducman, 2023, published scientific conference contribution Abstract: 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.
Keywords: metakaolin, alkali activated material, alkali activated foams, microwave irradiation
Published in DiRROS: 28.11.2023; Views: 257; Downloads: 108
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4. High temperature resistant fly-ash and metakaolin-based alkali-activated foamsKatja Traven, Mark Češnovar, Srečo D. Škapin, Vilma Ducman, 2021, original scientific article Abstract: Alkali-activated foams (AAFs) present one of the most promising materials for use in the construction sector. Their main advantages lie in their utilization of waste material and their ability to form at temperatures well below 100 °C, while still competing in performance with foamed glass or ceramics. The present body of research has focused on improving the thermal stability of fly-ash foams by i) adding metakaolin, and ii) changing the activator from sodium-based to potassium-based components. It has been confirmed that a certain increase in thermal resistance is achieved through the addition of metakaolin while changing activators played a crucial role. While sodium-based AAFs without metakaolin start to shrink at approximately 600 °C, samples that have had metakaolin added start to shrink at approximately 700 °C. Samples without metakaolin that have used a potassium activator start to shrink at approximately 800 °C, whereas potassium-based samples with the addition of metakaolin start to shrink at approximately 900 °C.
Keywords: alkali activated materials, geopolymers, high temperature, resistance, foams
Published in DiRROS: 01.08.2023; Views: 260; Downloads: 204
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5. Flame retardant behaviour and physical-mechanical properties of polymer synergistic systems in rigid polyurethane foamsBranka Mušič, Nataša Knez, Janez Bernard, 2022, original scientific article Abstract: In the presented work, the influence of two flame retardants—ammonium polyphosphates and 2,4,6-triamino-1,3,5-triazine on the polyurethane foam (PUR) systems were studied. In this paper, these interactive properties are studied by using the thermal analytical techniques, TGA and DTA, which enable the various thermal transitions and associated volatilization to be studied and enable the connection of the results with thermal and mechanical analysis, as are thermal conductivities, compression and bending behavior, hardness, flammability, and surface morphology. In this way, a greater understanding of what the addition of fire retardants to polyurethane foams means for system flammability itself and, on the other hand, how this addition affects the mechanical properties of PUR may be investigated. It was obtained that retardants significantly increase the fire resistance of the PURs systems while they do not affect the thermal conductivity and only slightly decrease the mechanical properties of the systems. Therefore, the presented systems seem to be applicable as thermal insulation where low heat conductivity coupled with high flame resistance is required.
Keywords: flammability, polyurethane polymer, foams, thermal conductivity, mechanical properties, open access
Published in DiRROS: 08.06.2023; Views: 348; Downloads: 169
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