51. Sustainable alkali-activated slag binders based on alternative activators sourced from mineral wool and glass wasteMajda Pavlin, Katja Koenig, Jakob Koenig, Uroš Javornik, Vilma Ducman, 2022, original scientific article Abstract: In the present study, four different locally available waste glass materials (bottle glass-BG, glass wool-GW, stone wool-SW and cathode-ray tube glass-CRTG) were treated with hot concentrated potassium hydroxide (KOH) in order to obtain alternative alkali activators (AAAs). We evaluated the suitability of the solutions obtained for use as AAAs in the production of AAMs. AAMs were prepared using electric arc furnace slag and selected AAAs with a higher content of dissolved Si. We evaluated the performance of the AAMs in comparison to that of slags activated with KOH or potassium-silicate (K-silicate). The compressive strength of the AAMs prepared with KOH-based AAAs were high when Si and Al were simultaneously abundant in the AAA (9.47 MPa when using the activator sourced from the CRTG), and low with the addition of KOH alone (1.97 MPa). The AAM produced using commercial K-silicate yielded the highest compressive strength (27.7 MPa). The porosity of the KOH-based AAM was lowest when an alternative BG-based activator was used (24.1%), when it was similar to that of the AAM prepared with a K-silicate. The BG-based activator had the highest silicon content (33.1 g/L), and NMR revealed that Si was present in the form of Q0, Q1 and Q2. The concentrations of toxic trace elements in the AAAs used for alkali activation of the slag were also determined, and leaching experiments were performed on the AAMs to evaluate the immobilisation potential of alkali-activated slag. In the SW AAAs the results show acceptable concentrations of trace and minor elements with respect to the regulations on waste disposal sites, while in the activators prepared from BG, CRTG and GW some elements exceeded the allowable limits (Pb, Ba, Sb, and As). Keywords: alkali activated materials/geopolymers, alternative activators, NMR, leaching Published in DiRROS: 08.06.2023; Views: 506; Downloads: 331
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52. Evaluation of sediments from the river Drava and their potential for further use in the building sectorVilma Ducman, Karmen Fifer Bizjak, Barbara Likar, Mitja Kolar, Ana Robba, Jernej Imperl, Mojca Božič, Boštjan Gregorc, 2022, original scientific article Abstract: Sedimentation is a naturally occurring process of allowing particles in water bodies to settle out of the suspension under a gravity effect. In this study, the sediments of the Drava River were fully investigated to determine the heavy metal concentrations along the river and their potential reuse in the construction sector. Naturally dehydrated sediments from the Drava River were tested as an additive for the production of fired bricks. The dredged sediments were used as a substitute for natural brick clay in amounts up to 50% by weight, and it was confirmed that up to 20% by weight of the added sediment could be used directly in the process without critically affecting performance. Finally, the naturally dehydrated sediments were also evaluated for their use as a filling material in the construction of levees. The natural moisture content of the dehydrated sediment was too high for it to be used without additives, so quicklime was added as an inorganic binder. The test results showed an improvement in the geotechnical properties of the material to such an extent that it is suitable as a filling material for levees. Keywords: sediment, pollution, clay industry, soil stabilization, open access Published in DiRROS: 31.05.2023; Views: 526; Downloads: 266
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53. Drava river sediment in clay brick production : characterization, properties, and environmental performanceMojca Božič, Lea Žibret, Davor Kvočka, Alenka Mauko Pranjić, Boštjan Gregorc, Vilma Ducman, 2023, original scientific article Abstract: The ever-growing worldwide demand for fired clay brick has resulted in the shortage of clay in many parts of the world. Therefore, there is a need to look for more sustainable alternative materials for the brick manufacturing. This study has investigated the potential use of the untreated Drava River sediment as a substitute material for clay in the production of fired bricks, with the research being conducted at both laboratory and industrial level. At the laboratory level, brick specimens were prepared by mixing clay with different river sediment proportions (ranging from 10 to 50 wt%) and were fired at 950 °C, with microstructural and various physical–mechanical properties being analyzed. Elevated carbonate content in Drava river sediment results in higher weight loss during firing at temperatures up to 950 °C, comparing to firing pure brick-making clay. Consequently, the addition of sediment increases porosity of fired bricks, which results in lowering of their mechanical properties. Results reveal that the compressive strength of the pure clay sample was 79.5 MPa, while the compressive strength of the sample with the addition of river sediment from 10 wt% to 50 wt% decreased from 73.9 MPa to 26.2 MPa, respectively. Despite the lower compressive strength, the 26.2 MPa is still above the limit value of 10 MPa specified in the standard EN 772–1 [1]. At the industrial level, hollow clay bricks were prepared with 20 wt% of the river sediment and fired in a tunnel kiln. Inclusion of the river sediment also decreased compressive strength from 38 MPa for pure mixture to 26 MPa for 20 wt% of the sediment addition, confirming usability of Drava sediment in brick production. In addition, LCA study has been conducted to evaluate the environmental impacts associated with the industrial production of classic bricks and bricks with the addition of the river sediment. The obtained results have shown that the bricks made with the addition of the Drava River sediment are sustainable and environmentally friendly and meet all the requirements specified in the relevant regulatory standard. Keywords: sediments, clay masonry units, LCA, properties Published in DiRROS: 30.05.2023; Views: 485; Downloads: 357
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54. Clay rich river sediments calcined into precursors for alkali activated materialsLea Žibret, Wolfgang Wisniewski, Barbara Horvat, Mojca Božič, Boštjan Gregorc, Vilma Ducman, 2023, original scientific article Abstract: Alkali activated materials (AAMs), a potential alternative to cement-based products or ceramics, can incorporate large amounts of currently landfilled aluminosilicate rich materials such as calcined clay-rich river sediments collected at hydropower plant dams. Untreated fresh sediment and untreated aged sediment intended to serve as AAM precursors were calcined to increase their amorphous content, then activated by Na or K-based silicate or hydroxide solutions and cured at 60 ◦C for three days.
Up to 30 mass % (ma%) of fly ash (FA) or ladle slag (LS) increased the mechanical performance. The phase composition and microstructure are analyzed using X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and mercury intrusion porosimetry to gain further insight into how the additives influence the final properties of the resulting AAMs. The main crystalline components of the prepared AAMs are quartz, illite/muscovite and feldspar. The amorphous content reaches up to 52.5 ma% in the Na-activated AAMs and up to 48.8 ma% in K-activated AAMs. The acquired results confirm the suitability of the investigated sediments as sole precursors for AAMs. The mechanical properties of the AAMs can be improved by adding FA and/or LS. Keywords: sediments, alkali activated materials, properties Published in DiRROS: 30.05.2023; Views: 486; Downloads: 386
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55. Antibacterial properties and cytotoxicity of 100% waste derived alkali activated materials : slags and stone wool-based bindersCaterina Sgarlata, Giovanni Dal Poggetto, Federica Piccolo, Michelina Catauro, Katja Traven, Mark Češnovar, Hoang Nguyen, Juho Yliniemi, Luisa Barbieri, Vilma Ducman, Isabella Lancellotti, Cristina Leonelli, 2021, original scientific article Abstract: In this study we compare the leaching behavior and the antibacterial and cytotoxic properties of 100% slag or stone wool derived alkali activated materials. The antibacterial activity was measured as the inhibiting capacity against two Gram- negative bacterial strains, Escherichia coli and Pseudomonas aeruginosa and one Gram-positive bacterial strain: Enterococcus faecalis. The cytotoxicity properties were tested on mouse embryonic fibroblast NIH-3T3 cell-line. It was proved that the high quality of the 3D aluminosilicate network of the consolidated materials obtained from powders of CaO or MgO-rich slags or stone wool, opportunely activated with NaO and/or Na-silicate, was capable of stabilizing heavy metal cations. The concentrations of leachate heavy cations were lower than the European law limit when tested in water. The effect of additives in the composites, basal fibers or nanocellulose, did not reduce the chemical stability and slightly influenced the compressive strength. Weight loss in water increased by 20% with basalt fibers addition, while it remained almost constant when nanocellulose was added. All the consolidated materials, cement-like in appearance, exhibited limited antibacterial properties (viability from 50 to 80% depending on the bacterial colony and the amount of sample) and absence of cytotoxicity, envisaging good acceptance from part of the final consumer and zero ecological impact. CaO-rich formulations can replace ordinary Portland cement (showing bacterial viability at 100%) with a certain capability for preventing the reproduction of the E. coli and S. aureus bacteria with health and environmental protection results. Keywords: antibacterial properties, cytotoxicity, alkali-activated materials, slag, stone wool, waste utilization, social acceptance Published in DiRROS: 22.05.2023; Views: 514; Downloads: 327
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56. Alkali activation of metallurgical slags : reactivity, chemical behavior, and environmental assessmentIsabella Lancellotti, Federica Piccolo, Katja Traven, Mark Češnovar, Vilma Ducman, Cristina Leonelli, 2021, original scientific article Abstract: Alkali-activated materials (AAMs) represent a promising alternative to conventional building materials and ceramics. Being produced in large amounts as aluminosilicate-rich secondary products, such as slags, they can be utilized for the formulation of AAMs. Slags are partially crystalline metallurgical residues produced during the high temperature separation of metallic and non-metallic materials in the steelmaking processes. In the present study, the electric arc furnace carbon or stainless steel slag (EAF) and secondary metallurgical slag such as ladle furnace basic slag (LS) were used as precursors in an alkali-activation process. EAF slag, with its amorphous fraction of about 56%, presented higher contents of soluble Si and Al species with respect to ladle slag R (35%). However, both are suitable to produce AAM. The leaching behavior shows that all the release values are below the regulation limit. All the bivalent ions (Ba, Cd, Cu, Ni, Pb, and Zn) are well immobilized in a geopolymeric matrix, while amphoteric elements, such as As and Cr, show a slight increase of release with respect to the corresponding slag in alkaline and aqueous environments. In particular, for Sb and As of AAM, release still remains below the regulation limits, while Mo presents an increase of leaching values that slightly exceeds the limit for landfill non-dangerous waste. Keywords: slag, aluminosilicate materials, chemical reactivity, cold consolidation, alkali activation, leaching test, open access Published in DiRROS: 22.05.2023; Views: 503; Downloads: 267
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57. Production and characterization of lightweight aggregates from municipal solid waste incineration fly-ash through single- and double-step pelletization processAlberto Ferraro, Vilma Ducman, Francesco Colangelo, Lidija Korat, Danilo Spasiano, Ilenia Farina, 2023, original scientific article Abstract: The performance of a cold-bonding pelletization process was investigated for lightweight aggregates (LWAs) production from municipal solid waste incineration (MSWI) fly-ash (FA), by including multiple waste materials in the aggregate mixture. Before pelletization, FA was pre-treated by washing with water, which led to a reduction of chloride (66.79%) and sulphate (25.30%) content. This was further confirmed by XRF and XRD analyses, which showed a reduction of chloride elements and the content of chlorine crystalline phases. The pelletization process was carried out using both single- and double-step methods. For single-step pelletization, all the mixtures contained 80% FA, combined with various compositions of cement (5, 10, and 15%) and granulated blast furnace slag (GBFS) (5, 10, and 15%). For the double-step pelletization 30% of cement and 70% of marble sludge (MS) were added to each of the previous mixtures. The apparent density of all the aggregates varied between 1.60 and 1.87 g cm 3, suggesting their suitability to be classified as LWAs. Aggregates produced from double-step pelletization showed improved characteristics, with water absorption capacity and open porosity generally lower compared to the corresponding aggregates from the single-step pelletization. The best values of compressive (crushing) strength (almost 11 MPa) were observed for double-step pelletization aggregates with initial cement: GBFS mixture of 15%:5%. Results from leaching tests showed an overall significant release of chloride and sulphate. Nevertheless, leaching from double-step pelletization aggregates was reduced by 1.73- 4.02 times for chloride and 1.58-5.67 times for sulphate, further suggesting that better performances are achievable through the addition of an aggregate second layer. Keywords: MSWI fly ash, lightweight aggregate, microtomography, open access Published in DiRROS: 03.05.2023; Views: 549; Downloads: 439
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58. The effect of the addition of construction & demolition waste on the properties of clay-based ceramicsBiljana Angjusheva, Vilma Ducman, Emilija Fidanchevski, 2022, original scientific article Abstract: Waste glass and reclaimed brick are types of construction and demolition waste (C&DW) that could potentially be used as secondary raw materials in the production of ceramics. Ceramics based on clay, waste demolished brick (5-15 wt.%) and waste glass (5-20 wt.%) were produced by pressing (P = 68 MPa) and subsequently sintered at 900, 950, 1000, and 1050 ° C for one hour. The physical and mechanical properties of the ceramics obtained were evaluated. The addition of demolished brick decreased the density and mechanical properties of the clay specimens and increased the water absorption. The incorporation of waste glass improved the sintering behavior and its mechanical properties. The addition of 20 wt.% waste glass and 10 wt.% waste demolished brick into the clay matrix improved the flexural strength by up to 20.6 % and decreased the water absorption by up to 22 %. The approach presented promotes an opportunity to recycle construction and demolition waste into alternative resource materials, and represents a positive contribution to the environment. Keywords: CDW, ceramics, properties Published in DiRROS: 25.04.2023; Views: 529; Downloads: 291
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