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Abstract: Mineral wool, i.e. rock and glass wool, represents considerable challenge after its functional-time runs out due to its small density leading to large volume consumption during transport and in landfills where it usually ends. Because rock wool is mineralogically and chemically a promising precursor material for alkali-activation, it was milled from few centimetres-decimeters long fibres to micron-sized fibres. Since fibres in alkali-activated materials generally show an increase in mechanical strength, especially the bending strength, 1 m% of additional fibres (basalt, cellulose (2 types), glass, polypropylene, polyvinyl alcohol and steel fibres) was used in the alkali mixture, that was curred at 40 °C for 3 days. Time dependence of the mechanical strengths of alkali- activated materials with and without additional fibres was followed. Maximal increase of compressive and bending strength after 28 days was reached with polypropylene fibres, i.e. it was 20% and 30% higher than compressive and bending strength of alkali- activated material without additional fibres respectively.
Keywords: secondary raw material, alkali activated material, foaming, homogenization, mechanical strength
Published in DiRROS: 21.12.2023; Views: 241; Downloads: 81
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Abstract: In recent years great attention has been placed by the building sector on alkali-activated technology based on metakaolin, fly ash and ground granulated blast furnace slag (GGBFS), but also on emerging precursors such as by-products from non-ferrous metallurgy. The present work focuses on the development of alkali-activated binders from two slags, one from primary and one from secondary copper production, which were finely milled, blended with GGBFS, and activated with K-based alkali silicate solution with a 1.7 SiO2/K2O molar ratio. The aggregate to paste mass ratio was 2. The mixtures were cast, and cured for a designated time at room temperature and 60% RH. The so-obtained paving blocks were then tested in accordance with European standard for concrete paving blocks. The following properties were measured: splitting tensile strength, abrasion resistance, slip and skid resistance, resistance to freeze-thaw and resistance to freeze-thaw in the presence of de-icing salts. Their properties were compared to those of commercially available concrete paving blocks, and it was found that the performance of the alkali-activated pavers was generally comparable with the concrete pavers, while certain properties (e.g., abrasion resistance, freeze-thaw resistance and freeze-thaw resistance in presence of de-icing salts) were considerably better.
Keywords: slags, alkali activated pavers, properties
Published in DiRROS: 21.12.2023; Views: 178; Downloads: 67
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Abstract: As part of the WOOL2LOOP project, the Slovenian National Building and Civil Engineering Institute (ZAG), in collaboration with Termit d.d. were responsible for the production of façade panels. An initial mix design was developed at ZAG, where alkali-activated façade panels were produced, primarily from stone wool waste, while production took place at Termit. The mix design was changed twice during the pilot production, before a final product with suitable durability was developed. A compressive strength of up to 60 MPa and bending strength of approximately 20 MPa was achieved. The mechanical properties, however, varied, due to the unevenly milled batches of the milled mineral wool. Milling on a larger scale is very challenging, and it is difficult to obtain consistent quality of the milled material. Once the correct curing process had been found, however, the panels produced showed good performance. Moreover, the results from leaching tests showed that the elevated concentrations of certain elements (Cr, As and Mo) did not exceed the legal limits for non- hazardous waste.
Keywords: waste mineral wool, alkali activated material, façade panels, pilot production, circular economy
Published in DiRROS: 28.11.2023; Views: 289; Downloads: 108
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Abstract: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Keywords: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Published in DiRROS: 22.11.2023; Views: 293; Downloads: 145
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Abstract: 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.
Keywords: critical raw materials, extraction, sewage sludge ash, municipal solid waste incineration ash, wood biomass ash
Published in DiRROS: 03.11.2023; Views: 375; Downloads: 138
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