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. Potential solutions for ▫$CO_2▫$-capturing technologies in the slovenian contextJanvit Golob, Dušan Klinar, Mihael Bricelj, 2012, izvirni znanstveni članek Povzetek: Human activities have caused an enormous rise of the CO2 concentration in the Earth’s atmosphere over the past 200 years. In order to alleviate this problem, the threats to and the concerns of the international community need to be converted into economic opportunities for national economies, which shall develop and utilize technological opportunities rather than simply accepting international obligations to reduce CO2 emissions. In the article we analyze technological possibilities in the Slovenian context as possible opportunities for promoting sustainable development based on regional, renewable resources. Beginning with an analysis of the amine process for CO2 concentration and its possibilities, we continue with CO2 chemistry examples, like the precipitation of calcium carbonate from Ca++ sources like lime or fly ash. Through the concept of product engineering we emphasize the need for a stepwise realization from the laboratory to a pilot plant and then to the industrial scale. The growth of biomass through forestry or algae production can provide an additional CO2 sink. However, for an efficient technical solution and implementation a close working relationship between biologists and engineers is required. Ključne besede: CO2 minimization, technological opportunities, amine concentration, CO2 chemistry, forestry, algae production, fly ash CO2 absorption Objavljeno v DiRROS: 05.08.2024; Ogledov: 95; Prenosov: 70
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3. Adsorption efficiency of cadmium (II) by different alkali-activated materialsNataša Mladenović Nikolić, Ljiljana Kljajević, Snežana B. Nenadović, Jelena Potočnik, Sanja Knežević, Sabina Dolenec, Katarina Trivunac, 2024, izvirni znanstveni članek Povzetek: The objective of this study was to demonstrate the potential utilization of fly ash (FA), wood ash (WA), and metakaolin (MK) in developing new alkali-activated materials (AAMs) for the removal of cadmium ions from waste water. The synthesis of AAMs involved the dissolution of solid precursors, FA, WA, and MK, by a liquid activator (Na2SiO3 and NaOH). In concentrated solutions of the activator, the formation of an aluminosilicate gel structure occurred. DRIFT spectroscopy of the AAMs indicated main vibration bands between 1036 cm−1 and 996 cm−1, corresponding to Si-O-Si/Si-O-Al bands. Shifting vibration bands were seen at 1028 cm−1 to 1021 cm−1, indicating that the Si-O-Si/Si-O-Al bond is elongating, and the bond angle is decreasing. Based on the X-ray diffraction results, alkali-activated samples consist of an amorphous phase and residual mineral phases. The characteristic “hump” of an amorphous phase in the range from 20 to 40◦ 2θ was observed in FA and in all AWAFA samples. By the XRD patterns of the AAMs obtained by the activation of a solid three-component system, a new crystalline phase, gehlenite, was identified. The efficiency of AAMs in removing cadmium ions from aqueous solutions was tested under various conditions. The highest values of adsorption capacity, 64.76 mg/g (AWAFA6), 67.02 mg/g (AWAFAMK6), and 72.84 mg/gmg/g (AWAMK6), were obtained for materials activated with a 6 M NaOH solution in the alkali activator. The Langmuir adsorption isotherm and pseudo-second kinetic order provided the best fit for all investigated AAMs. Ključne besede: fly ash, metakaolin, wood ash, adsorption kinetics, cadmium (II) Objavljeno v DiRROS: 23.05.2024; Ogledov: 273; Prenosov: 237
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4. Validation of the recycled backfill material for the landslide stabilization at a railway lineKarmen Fifer Bizjak, Barbara Likar, 2024, izvirni znanstveni članek Povzetek: In mountain areas landslides many times endanger safety of transport infrastructures, and these must be stabilized with retaining wall structures. In this paper the validation of a new composite as a backfill material for landslide stabilization with a large scale demo retaining wall is presented. The new composite was made from residues of paper industry, which uses for its production deinking process. New composite was validated with the laboratory tests, construction of small demo sites and at the end with a large demo retaining wall structure with a length of 50 m. It was concluded that the paper sludge ash and the paper sludge are in proportion 70:30, compacted on the optimal water content and maximum dry density, reached sufficient uniaxial compressive and shear strength. However, the composite's hydration processes required the definition of an optimal time between the composite mixing and installation. In 2019, the retaining wall structure from the new composite was successfully built. The large demo structure is an example of the knowledge transfer from the laboratory to the construction site, in which composite and installing technology could be verified. Ključne besede: landslides, recycled backfill material, paper sludge ash, geotechnical composite, railway line, recycled material, environment Objavljeno v DiRROS: 26.03.2024; Ogledov: 297; Prenosov: 222
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5. The use of paper industry side product in constructionBarbara Likar, Laura Vovčko, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: The amount of waste material and side products of various industrial plants is increasing, which leads into waste accumulation and lack of space in disposal landfills. Paper industry, with its side products paper sludge and ash, faces these same issues. To reduce the accumulation of these materials, we explored the possibility of their use in construction. At first a series of geomechanical tests was conducted on a product consisting of fly ash and bottom ash. Based on the laboratory results test fields were constructed, where the preparation and installation technologies were tested. The fields were exposed to the atmospheric conditions, so durability of the product in the natural environment was proven. Since the composition of both fly ash and bottom ash depends on the paper industry process, a continuous monitoring of their characteristics was established. Ključne besede: paper industry, fly ash, bottom ash, construction material, geomechanical properties Objavljeno v DiRROS: 05.03.2024; Ogledov: 347; Prenosov: 142
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6. Alternative alkali activators based on waste bottle glass and waste cathode-ray tube glassKatja Koenig, Katja Traven, Vilma Ducman, 2021, objavljeni znanstveni prispevek na konferenci Povzetek: Alkali-activated binders are an environmentally friendly alternative to Portland cement, particularly when locally-available raw materials are used. It is well known that alkali activation with a sodium silicate activator generates a hardened binder with higher compressive strength than a binder hardened with sodium hydroxide. As the alkali-silicate activators are produced through energy extensive processes, and their use can significantly increase the carbon footprint of the final products, it is of great significance to develop alternative alkaline activators based on locally-available waste materials. This article assesses the potential to apply waste bottle glass and waste cathode-ray tube (CRT) glass to synthesise alternative alkali activators by the hydrothermal method. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to determine silicon and aluminium content in the alternative activators. The influence of dissolution process parameters (time, temperature, particle size) on the concentrations of silicon and aluminium in the alternative activators was investigated. The alternative activators with silicon concentration up to 19 g/L and aluminium concentration up to 0.9 g/L were prepared at T = 120 °C and boiling time 24 h. The alternative alkali activators and, for comparison, also commercial sodium silicate were used in the alkali activation of fly ash powder. The formed pastes were cured at 70 °C for 72 h. Mechanical strength measurements indicated that alkali activation of fly ash with the optimal alternative activator yielded hardened paste with compressive strength of 33 MPa. However, the compressive strength of hardened paste prepared from fly ash and commercial sodium silicate reached 70 MPa. Part of this difference can be ascribed to the lower density of hardened pastes prepared with alternative activators. Ključne besede: alkali -activated materials, alternative alkali activators, waste bottle glass, waste cathode -ray tube glass, fly ash, hydrothermal method Objavljeno v DiRROS: 25.01.2024; Ogledov: 382; Prenosov: 239
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7. Evaluation of ash pozzolanic activity by means of the strength activity index test, frattini test and DTA/TG analysisSabina Dolenec, Vilma Ducman, 2018, izvirni znanstveni članek Povzetek: The pozzolanic activity of five different types of ash was studied using various direct and indirect methods. In addition to strength activity index (SAI) determination and the Frattini test, ash pozzolanicity was assessed via differential thermal and thermogravimetric analyses (DTA/TG) after curing for 7, 28 and 90 days. The results showed that, due to their respective mineralogical, chemical and physical characteristics, the ashes exhibited different levels of pozzolanic activity in terms of the amount of lime with which they could chemically bind, as well as reaction kinetics. Although SAI and Frattini test results were not in agreement in the case of some of the ashes, DTA/TG analysis revealed that a certain amount of portlandite was consumed, thus confirming the occurrence of a pozzolanic reaction. The results also showed that ashes with higher amounts of reactive SiO2 were more reactive, while those with higher BET surface areas displayed a faster pozzolanic reaction rate. Ključne besede: biomass ash, DTA/TG, fly ash, Frattini test, pozzolanic activity, SAI Objavljeno v DiRROS: 11.12.2023; Ogledov: 390; Prenosov: 190
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8. Flame spread behaviour of Polydimethylsiloxane (PDMS) membranes in 1 g and µg environmentsWilson Ulises Rojas Alva, Frederik Møller-Poulsen, Sze Lok Man, Cameron Creamer, David Hanna, Grunde Jomaas, 2022, izvirni znanstveni članek Povzetek: Diffusion flame behaviour and silica ash (SiO2) production were experimentally studied for various Polydimethylsiloxane (PDMS) membrane thicknesses (0.125 mm to 1.0 mm) in normal gravity and during microgravity flight experiments. The flames were established on vertical samples (300 mm in length) and subjected to either opposed or concurrent forced flows (both laminar and turbulent), assimilating the NASA Test 1 that is in use for spacecraft material selection. The opposed flame spread rate was observed to be steady and could be estimated using classical theory. Under concurrent flow, the flame spread rate was only steady for very high forced flows. The opposed flame-spread rate ranged from 0.5 to 1.5 mm/s, while the concurrent case ranged between 0.1 and 12 mm/s. The transport of silica ash (SiO2) was found to affect the heat balance of the concurrent flame spread in a manner that resulted in unsteady flame spread. For opposed flame spread, on the other hand, the transport of silica ash showed to be irrelevant. The extinction behaviour for the concurrent flame spread was heavily dominated by the transport of silica-ash, while for opposed flames, extinction was due to kinetics (at high forced flows). In microgravity environments, the transport and deposition of silica ash is anticipated to dominate flame spread and near-limit as well. These results suggest that silica-based products might be less flammable in microgravity than other similar materials such as common thermoplastics (PP or PE) used as wire jackets. Ključne besede: silicone burning, spacecraft fire safety, flame spread, near-limit, silica-ash Objavljeno v DiRROS: 13.11.2023; Ogledov: 529; Prenosov: 193
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9. Recovery of phosphorus and metals from the ash of sewage sludge, municipal solid waste, or wood biomass : a review and proposals for further useSara Tominc, Vilma Ducman, Wolfgang Wisniewski, Terttu Luukkonen, Kirkelund Gunvor M., Ottosen Lisbeth M., 2023, izvirni znanstveni članek Povzetek: This review provides an overview of methods to extract valuable resources from the ash fractions of sewage sludge, municipal solid waste, and wood biomass combustion. The resources addressed here include critical raw materials, such as phosphorus, base and precious metals, and rare earth elements for which it is increasingly important to tap into secondary sources in addition to the mining of primary raw materials. The extraction technologies prioritized in this review are based on recycled acids or excess renewable energy to achieve an optimum environmental profile for the extracted resources and provide benefits in the form of local industrial symbioses. The extraction methods cover all scarce and valuable chemical elements contained in the ashes above certain concentration limits. Another important part of this review is defining potential applications for the mineral residues remaining after extraction. Therefore, the aim of this review is to combine the knowledge of resource extraction technology from ashes with possible applications of mineral residues in construction and related sectors to fully close material cycle loops. Ključne besede: critical raw materials, extraction, sewage sludge ash, municipal solid waste incineration ash, wood biomass ash Objavljeno v DiRROS: 03.11.2023; Ogledov: 609; Prenosov: 249
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10. Use of fly ash and phosphogypsum for the synthesis of belite-sulfoaluminate clinkerSabina Dolenec, Lea Žibret, Emilija Fidanchevska, V. Jovanov, Biljana Angjusheva, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Fly ash and phosphogypsum were used as Naturally Occurring Radioactive Materials (NORM) by-products for the synthesis of belite-sulfoaluminate clinkers. The influence of raw mixture composition and firing temperature was investigated. Clinkers and cements were examined by X-ray powder diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The compressive strength of the cements was determined after 28 days. Clinker phases identified included ye’elimite, ß-phase of belite, ternesite and gehlenite, while the main hydration product of the cement pastes was ettringite. The results showed that belite-sulfoaluminate cements can be fabricated with a compressive strength of 45.9 N/mm2 by firing the raw mixture (70 wt.% marl, 10 wt.% bauxite and 20 wt.% phosphogypsum) at a temperature of 1320°C/1h. Ključne besede: clinker, microstructure, fly ash, gypsum, calcium sulphoaluminate Objavljeno v DiRROS: 27.10.2023; Ogledov: 543; Prenosov: 242
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