1. Stabilization of river dredged sediments by means of alkali activation technologyKarmen Fifer Bizjak, Lea Žibret, Mojca Božič, Boštjan Gregorc, Vilma Ducman, 2024, izvirni znanstveni članek Povzetek: Purpose
Alkali activation process has been applied to fresh river clay-rich sediments in order to increase their mechanical properties and make them suitable for soil stabilization.
Materials and methods
Dredged sediments were mixed with up to 30 mass percent (ma%) of fly ash (FA) or ladle slag (LS) and after curing for 3 days at 60 °C, the bending and compressive strength have been determined. The mixtures which exhibited the highest strengths were further optimized for being used in soil stabilization. For this purpose, the sediment was stabilized with 4 ma% of quicklime (QL) and after 1 h 30 ma% of FA with alkali activator was added and cured for 1, 7 and 28 days.
Results
The stabilized sediment has a significantely better geomechanical performance in comparison with the sediment alone. Stabilizing the dredged sediment using alkali activation technology provides high enough strengths to eventually make it suitable for anti-flood embankments.
Conclusions
The results confirmed the suitability of the investigated technology for soil stabilization. Ključne besede: river sediment, alkali activated materials, ladle slag, fly ash, mechanical strength, soil stabilization Objavljeno v DiRROS: 09.09.2024; Ogledov: 317; Prenosov: 4723 Celotno besedilo (1,41 MB) Gradivo ima več datotek! Več... |
2. Increasing the amorphous content in river sediments intended for supplementary cementitious materials using flame synthesisWolfgang Wisniewski, Jozef Kraxner, Lea Žibret, Dušan Galusek, Vilma Ducman, 2024, izvirni znanstveni članek Povzetek: Dredged river sediments are currently a waste material which is mainly landfilled or reintegrated into rivers. They can also be used as a renewable resource for the construction sector. Pre- treatments at high temperatures allow their use for more advanced applications such as supplementary cementitious materials (SCMs) or as a precursor for alkali activated materials (AAMs). The work presented here shows that flame synthesis can be used to almost completely vitrify such sediments and increase their leachability for Al and Si beyond the levels achieved by conventional calcination at 750–950 ◦C for 1h.
The reactivity of the prepared samples was analyzed via the Si and Al solubility in 10 M NaOH and was generally increased by the applied treatments but maximized by flame synthesis. Their microstructure was analyzed using scanning electron microscopy and their phase composition was monitored using X-ray diffraction. The results show an almost complete amorphization of the sediments by flame synthesis, however their reactivity does not increase at the same rate. Ključne besede: sediments, SCM, vitrification, properties Objavljeno v DiRROS: 23.05.2024; Ogledov: 552; Prenosov: 338 Celotno besedilo (2,50 MB) Gradivo ima več datotek! Več... |
3. Manual for use of Al-containing residues in low-carbon mineral bindersSabina Dolenec, Katja Malovrh Rebec, Anja Lešek, Katarina Šter, Lea Žibret, Gorazd Žibret, Klemen Teran, Emil Pučko, Ildikó Merta, Bojan Poletanovic, Elena Yaneva, Peter Kesserű, Ildikó Kovács, Bence Kószó, Alexandra Németh, Richard Laucournet, Mustafa Hadžalić, Emilija Fidanchevski, Biljana Angjusheva, Vojo Jovanov, Miloš Nenadović, Snežana B. Nenadović, Ivana Vukanac, Liljana Kraljević, Mojca Loncnar, Andrej Ipavec, 2020, slovar, enciklopedija, leksikon, priročnik, atlas, zemljevid Povzetek: Današnje družbe si ni več mogoče predstavljati brez sodobne infrastrukture, ki temelji na uporabi različnih materialov ter zahteva veliko porabo energije. Vzporedno s proizvodnjo materialov, nastajajo ogromne količine različnih industrijskih in rudarskih ostankov (odpadki/stranski proizvodi), ki jih trenutno ne izkoriščamo, sama odlagališča pa so premalo raziskana. Cilj Evropske unije (EU) je povečati učinkovito rabo virov in ponudbo sekundarnih surovin z recikliranjem, popisom odpadkov iz rudarskih in drugih industrijskih dejavnosti ter njihova ponovna uporaba. Veliko industrijskih in rudarskih odpadkov je obogatenih z aluminijem (Al), zato lahko nadomeščajo naravne vire Al v mineralnih veznih, vendar njihova uporaba zahteva obsežno poznavanje njihovih kemijskih, mineraloških, radioloških in fizikalnih lastnosti. Priročnik, ki so ga pripravili partnerji projekta RIS-ALiCE obravnava zakonodajne vidike, ki urejajo uporabo sekundarnih surovin v gradbenih proizvodih, opis najpogostejših industrijskih in rudarskih ostankov, ki vsebujejo Al (nahajališča boksitov, rdeče blato, jeklarske žlindre, pepeli iz različnih industrij, itd.), potencial njihove ponovne uporabe in njihov ekonomski vidik, potencialne zahteve/ovire za uporabo sekundarnih surovin v cementni industriji in opis belitno-sulfoaluminatnih cementov, ki so obetavna rešitev za izvajanje krožnega gospodarstva z uporabo velikih količin odloženih industrijskih in rudarskih odpadkov, bogatih z Al. Ključne besede: gradbeni proizvodi, ponovna uporaba, ekonomski vidik, industrija cementa, krožno gospodarstvo, industrijski odpadki, zakonodaja, elektronske knjige Objavljeno v DiRROS: 22.01.2024; Ogledov: 639; Prenosov: 321 Celotno besedilo (4,51 MB) Gradivo ima več datotek! Več... |
4. Use of steel slag for the synthesis of belite-sulfoaluminate clinkerLea Žibret, Martina Cvetković, Maruša Mrak, Mojca Loncnar, Andrej Ipavec, Sabina Dolenec, 2020, objavljeni znanstveni prispevek na konferenci Povzetek: Belite-sulfoaluminate (BCSA) cements are low-carbon mineral binders, which require low energy consumption and allow the incorporation of various secondary raw materials in the clinker raw meal. In this study two types of unprocessed steel slags, coming from stainless steel production, were incorporated in the BCSA clinkers. The clinker phase composition, clinker reactivity, and the compressive strength of the cement were studied to evaluate the possible use of the slag in BCSA clinkers. The cement clinkers were synthesized by using natural raw materials, white titanogypsum, mill scale, as well as two different steel slags: (i) EAF S slag, which is a by-product of melting the recycled steel scrap in an electric arc furnace, and (ii) la dle slag as a by-product of the processes of secondary metallurgy, in various quantities. Raw mixtures with two different targeted phase compositions varying in belite, calcium sulfoaluminate and ferrite phases were sintered at 1250 °C. Clinker phases were determined by Rietveld quantitative phase analysis, while their distribution, morphology and incorporation of foreign ions in the phases were studied by SEM/EDS analysis. The clinker reactivity was determined by isothermal calorimetry. BCSA cements were prepared by adding titanogypsum. The compressive strength of the cement pastes was determined after 7 days of hydration. The presence of a predicted major clinker phases was confirmed by Rietveld analysis, however periclase was also detected. Microscopy revealed subhedral grains of belite and euhedral grains of calcium sulfoaluminate phases, while ferrite occurred as an interstitial phase. The results showed differences in the microstructure and reactivity of the clinker and cement, which can be attributed to varying amounts of ettringite due to different slag types Ključne besede: belite-sulfoaluminate cement, cement clinker, steel slags, clinker microstructure, cement reactivity Objavljeno v DiRROS: 19.01.2024; Ogledov: 774; Prenosov: 312 Celotno besedilo (18,89 MB) Gradivo ima več datotek! Več... |
5. Effect of the cooling regime on the mineralogy and reactivity of belite-sulfoaluminate clinkersSabina Dolenec, Katarina Šter, Maruša Mrak, Klara Žagar, Andrej Ipavec, Lea Žibret, 2020, izvirni znanstveni članek Povzetek: This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days. Ključne besede: clinkers, belite, calcium sulfoaluminate, cooling, microstructure, reactivity Objavljeno v DiRROS: 20.12.2023; Ogledov: 622; Prenosov: 277 Celotno besedilo (4,18 MB) Gradivo ima več datotek! Več... |
6. 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: 740; Prenosov: 348 Celotno besedilo (2,01 MB) Gradivo ima več datotek! Več... |
7. Development of a simple gelatin-based sensing platform for the sensitive label-free impedimetric detection of SARS-CoV-2Alnilan Cristina Barros Lobato, Maja Šubic, Tea Romih, Lea Žibret, Dino Metarapi, Mojca Benčina, Roman Jerala, Kristijan Vidović, Samo B. Hočevar, Nikola Tasić, 2023, izvirni znanstveni članek Objavljeno v DiRROS: 07.08.2023; Ogledov: 837; Prenosov: 419 Celotno besedilo (1,10 MB) Gradivo ima več datotek! Več... |
8. Effects of the temperature on the pore evolution during sintering of the belite-sulfoaluminate cement clinker using x-ray computed microtomographySabina Dolenec, Lidija Korat, Maruša Mrak, Andrej Ipavec, Lea Žibret, 2020, izvirni znanstveni članek Povzetek: In this paper, the effects of the sintering temperature on the pore evolution of the belite-sulfoaluminate cement clinker were evaluated. Belite-sulfoaluminate cement clinker with a targeted composition of 65 w/% b-belite, 20 w/% calcium sulfoaluminate and 10 w/% ferrite was sintered at three different temperatures: 1200 °C, 1250 °C and 1300 °C. To quantitatively evaluate the pore evolution during sintering, a 3D microstructure reconstruction by micro-CT was used. From the data, the pore volume frac- tion and pore number were extracted and compared, and the pore size distribution with the sintering temperature was obtained as well. Additionally, the pore shape and distribution were displayed in 3D based on actual microstructure data. Clinker samples were also characterized by Hg-intrusion porosimetry and gas sorption. The changes in the pore evolution occurred to a larger extent when sintering at 1300 °C. Apart from a significant porosity decrease, pore coarsening was evident at this temperature, reducing their connectivity and shrinkage of the clinker. Simultaneously, the bulk and apparent densities increased with the temperature due to densification, while the BET surface area of the studied clinkers decreased, indicating the rounding of pores and particle coalescence with an increasing grain growth. Ključne besede: klinker, belit-sulfoaluminat, razvoj por, sintranje Objavljeno v DiRROS: 04.08.2023; Ogledov: 768; Prenosov: 356 Celotno besedilo (2,27 MB) Gradivo ima več datotek! Več... |
9. The Incorporation of steel slag into belite-sulfoaluminate cement clinkersLea Žibret, Katarina Šter, Maruša Mrak, Mojca Loncnar, Sabina Dolenec, 2021, izvirni znanstveni članek Povzetek: The potential use of steel slag from treated steel slag in belite-sulfoaluminate cements was investigated in this study. Cement clinkers with two phase compositions were synthesized, allowing the incorporation of different amounts of steel slag. The phase composition and microstructure of cement clinkers at three different sintering temperatures were studied by X-ray powder diffraction and the Rietveld method, as well as scanning electron microscopy with energy dispersive spectrometry. The results showed that the targeted phase composition of clinkers was achieved at a sintering temperature of 1250%C. However, a higher amount of perovskite instead of ferrite was detected in the clinker with a higher content of Ti-bearing bauxite. Apart from the main phases, such asbelite, calcium sulfoaluminate, and ferrite, several minor phases were identified, including mayenite, perovskite, periclase, and alkali sulfates. In both clinker mixtures, a higher content of MgO in the steelslags resulted in the formation of periclase. Furthermore, the hydration kinetics and compressive strength at 7 and 28 days were studied in two cements prepared from clinkers sintered at 1250%C. As evidenced by the results of isothermal calorimetry, the hydration kinetics were also influenced by the minor clinker phases. Cement with a higher content of calcium sulfoaluminate phase developed a higher compressive strength. Ključne besede: cements, BCSA, steel slag, secundary row materials, microstructure, clinker phase Objavljeno v DiRROS: 01.08.2023; Ogledov: 667; Prenosov: 329 Celotno besedilo (5,50 MB) Gradivo ima več datotek! Več... |
10. Neogene block rotation inside the dextral fault zone at the Adriatic-European collision zone: reexamination of existing resultsLea Žibret, Gorazd Žibret, 2023, izvirni znanstveni članek Povzetek: The study focused on the post-Middle-Miocene stress analysis within the dextral strike-slip zone of the Dinaric fault system in the collision zone between the European plate, the Adria microplate and the Pannonian Domain. Block rotations were studied by re-examination of available paleostress data and their spatial distribution. The results are in agreement with the existing block model of the area, indicating CCW rotations within blocks between the main strike-slip faults in which rotation angle increases from W to E. The improved kinematic model, which is proposed in this study, will contribute to the knowledge on the kinematics within the complex collision zones and improve the seismic hazard models. Ključne besede: collision zone, NW External Dinarides, Southern Alps, paleostress tensor, strike-slip zone, block rotation Objavljeno v DiRROS: 06.07.2023; Ogledov: 706; Prenosov: 283 Celotno besedilo (8,47 MB) |