1. Circularity and longevity of alkali-activated materials : case-study using rock wool as a precursorBarbara Horvat, Sara Tominc, 2025, published scientific conference contribution Abstract: Alkali-activated materials (AAMs) are being envisaged as a future alternative to cements because AAMs (i) can be made solely from locally available secondary raw materials and (ii) because of their low energy consumption during synthesis. However, products that cannot be reused should never enter the market. Therefore, the circular economy viability of AAMs was studied by reusing (alkali-activated) pulverised rock wool in alkali activation synthesis until the theoretically determined limit leading to the efflorescence would be reached. While 25% of the maximal allowed liquid alkali did not offer significant mechanical performance, 50, 75 and 100% of allowed alkali ended up with 15, 20 and 20 MPa, respectively, which is only 5 MPa lower than AAM made with the same technique (pressing) in a one-step approach. Therefore, if the initial AAM does not reach the efflorescence limit, it could still be used as a precursor before it becomes waste.
Keywords: kamena volna, alkalijsko aktivirani materiali, mikrovalovno obsevanje, elektromagnetna dehidracija, krožni modeli, linearni modeli
Published in DiRROS: 16.07.2025; Views: 523; Downloads: 262
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2. Late-microwave irradiation of alkali-activated waste glass wool : linking dehydration rate with thermomechanical behaviourBarbara Horvat, Anže Tesovnik, Branka Mušič, 2025, published scientific conference contribution Abstract: Building and civil engineering conventional inorganic binding materials represent a significant burden for the environment, leading to the search for more sustainable materials. One of the potential solutions is alkali-activated materials (AAMs), which can be made solely from waste materials and at lower temperatures. However, reaction rate and solidification time depend on the precursor used. To enhance the speed of solidification, the curing temperature can be increased, but from the inside out not to create the crust on the surface, which would hinder the dehydration. Therefore, three mixtures of alkali-activated glass wool, a slow-in-alkali media solidifying precursor, were irradiated with low- and high-power microwaves in the late curing stage till complete dehydration, to determine the influence of artificial volumetric solidification onto thermomechanical behaviour of the AAM. As the electromagnetic power increased, the damages in the AAM became more severe, resulting in a reduction in mechanical strength.
Keywords: microwave irradiation, electromagnetic dehydration, glass wool, alkali-activated materials, mechanical performance
Published in DiRROS: 07.04.2025; Views: 719; Downloads: 495
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3. Overview of the impacts of additive production techniques on the environment : production of continuous fibers, direct laser sintering of metals and selective laser sintering techniquesBranka Mušič, Barbara Horvat, 2025, published scientific conference contribution Abstract: Additive manufacturing (AM) has experienced significant growth in recent years, emerging as a transformative technology with broad applications across various industries. This review explores the advantages, disadvantages, and environmental impacts of AM, an important area of consideration as this technology continues to gain popularity. By analyzing existing literature, we assess the challenges associated with AM processes, particularly in comparison to traditional manufacturing methods. AM has the greatest potential to contribute to sustainable development by the production of lightweight components and complex industrial products with intricate designs. These products are made with minimal material usage. Consequently, also waste and emissions are reduced, which are significant environmental advantages. Overall, this review highlights the importance of AM as a tool for advancing sustainability in manufacturing and offers valuable insights for Continuous Fiber Fabrication, Direct Metal Laser Sintering, and Selective Laser Sintering techniques to enhance their competitive advantage while reducing their environmental impact.
Keywords: additive manufacturing, 3D print, continuous fiber fabrication, direct metal laser sintering, selective laser sintering, AddCircles
Published in DiRROS: 07.04.2025; Views: 732; Downloads: 336
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4. Rapid immobilisation of chemical reactions in alkali-activated materials using solely microwave irradiationAnže Tesovnik, Barbara Horvat, 2024, original scientific article Abstract: Efflorescence, a time-dependent and water-driven phenomenon, is a major concern inalkali-activated materials (AAMs), impacting their practical use and preservation in a time-frozen state for post-characterisation. Although a method for stopping chemical reactions in conventional cements exists, it is time-consuming and not chemical-free. Therefore, this study explored the effects of low-power microwave-induced dehydration on efflorescence, mechanical performance, and structural integrity in AAMs, to create an alternative and more “user-friendly” dehydration method. For this purpose, several mixtures based on secondary raw (slag, fly ash, glass wool, and rock wool) and non-waste (metakaolin) materials were activated with a commercial Na-silicate solution in ratios that promoted or prevented efflorescence. Characterisation techniques, including Fourier-transform infrared spectroscopy and X-ray diffraction, showed that microwave dehydration effectively removed water without altering crystallinity, while mercury intrusion porosimetry and compressive strength tests confirmed increased porosity. In addition to being an efficient, time-saving, and solvent-free manner of stopping the reactions in AAMs, microwave irradiation emerged as an innovative, chemical-free method for evaluating curing finalisation and engineering foams in a stage when all other existing methods fail. However, the artificially provoked efflorescence in aged dehydrated AAMs connected the slipperiness of AAM with the instant extraction of Na, which raised the need for further research into alternative alkali replacements to evaluate the practical use of AAM.
Keywords: materials chemistry, alkali-activated materials, geopolymers, slag, fly ash, rock wool, glass wool, metakaolin, microwave irradiation, dehydration, stopping chemical reactions, efflorescence
Published in DiRROS: 23.12.2024; Views: 977; Downloads: 642
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5. Dehydration with microwave irradiationAnže Tesovnik, Barbara Horvat, 2024, complete scientific database of research data Abstract: The dataset supports the results shown in the tables and figures in the article entitled “Rapid immobilisation of chemical reactions in alkali-activated materials using solely microwave irradiation” (doi: https://doi.org/10.3390/min14121219). It contains measurements of mechanical and structural evaluation, as well as chemical and mineralogical analysis.
Keywords: measurments, alkali-activated materials, geopolymers, slag, fly ash, rock wool, glass wool, metakaolin, microwave irradiation, dehydration, stopping of chemical reactions, efflorescence
Published in DiRROS: 12.08.2024; Views: 1296; Downloads: 11685
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6. 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: 2938; Downloads: 1078
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7. 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, published scientific conference contribution Abstract: 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.
Keywords: flame retardants, polyurethane, alkali activated material, metakaolin, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 3948; Downloads: 875
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8. Waste rubber incorporated in the alkali-activated metakaolin’s aluminosilicate network enhanced by microwave irradiationBarbara Horvat, Branka Mušič, 2024, published scientific conference contribution Abstract: 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.
Keywords: secondary raw material, alkali activated material, waste rubber, metakaolin, encapsulation of organic in inorganic material, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 3159; Downloads: 990
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