1. Ornate Bairdiidae (Ostracoda) in 3 dimensions : exploring carapace morphology and pore canals of Triebelina van den Bold, 1946, Nodobairdia Kollmann, 1963 and Mirabairdia Kollmann, 1963Marie-Béatrice Forel, Nathalie Poulet-Crovisier, Lidija Korat, Rosalie F. Maddocks, 2024, original scientific article Abstract: Marine ostracods of the family Bairdiidae Sars, 1888 have an evolutionary history starting from the Ordovician with an explosive diversification of ornate forms during the Triassic. Representatives of the family are notoriously homeomorphic, which makes their taxonomy a major challenge of modern ostracodology. Their classification has thus been problematic since the 1970s. Here we present the first CT-scan investigation of recent and fossil ornate Bairdiidae valves in order to characterize and evaluate the taxonomic significance of unexploited characters, such as pores and pore canals. Thanks to 3D tomography, we explore the distribution of pores at the surface and the pathway of pore ca- nals within the valve wall of the recent genus Triebelina van den Bold, 1946 and the Triassic genera Nodobairdia Kollmann, 1963 and Mirabairdia Kollmann, 1963. In Triebelina indopacifica van den Bold, 1946, we describe an unexpected system of double pore canals, so far unknown in ostracods. We confirm that pore systems in Triebelina have largely intramural positions. In the Triassic Bairdiidae (Nodobairdia mammilata Kollmann, 1963 and Mirabairdia pernodosa Kollmann, 1963), we recognize simple unrimmed and massively nodular pores as well as marginal pores. Lateral normal pores of the Triassic specimens appear to be mostly in intra-solum positions. Although still exploratory and at the limits of the tomographic resolution, these observations provide new evidence to reject the formerly proposed synonymy of Triassic genera with Triebelina, which obstructed the establishment of a phylogenetic classification. Keywords: ostracods, ornate Bairdiidae, morphology, normal pore canals, CT-scan, 3D analysis Published in DiRROS: 08.03.2024; Views: 349; Downloads: 265
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2. Characterisation of a 3D-printed alkali-activated material based on waste mineral wool at room and elevated temperaturesMajda Pavlin, Barbara Horvat, Romana Cerc Korošec, Rok Capuder, Lidija Korat, Vilma Ducman, 2024, original scientific article Keywords: recycling, alkalijsko aktivirani materiali, 3D print, mineralna volna Published in DiRROS: 25.01.2024; Views: 488; Downloads: 286
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3. Temperature pre-treatment of gypsum for powder based 3D printing technologyVesna Zalar Serjun, Lidija Korat, 2021, published scientific conference contribution Abstract: In recent years many researchers have been involved in studies in the field of pre-treatment of various raw materials. Temperature treatment of materials results in several advantages, which have been already recognised and successfully applied in various fields of applications. Where at the same time, the practices has been adopted also in the field of 3D printing. Enhanced strength and stiffness, assuring desirable performance criteria of the 3D printed models, reflect the most important characteristics. 3D printing binder jetting technology is based on the application of liquid binders onto powdered material, where gypsum powders have been commercially used as a base raw material. As natural raw materials can be replaced by other materials, such as recycled industrial by products, the aim of this research work was to evaluate the potential usage of three synthetic gypsum powders from different industrial processes for 3D printing. The investigation covered (a) mineralogical and microstructural characteristics of gypsums from different origin and (b) the effect of pre-treatment of gypsum powders at different temperatures (up to 500 °C). On the basis of the results, the most promising temperature regime for each different waste gypsum powder treatment, reflecting in the most optimal setting time, was defined. Synthetic gypsums were characterized by X-ray diffraction (QXRD), scanning electron microscopy (SEM) and differential thermal analysis (TG/DTA). The results showed that all three synthetic gypsums (calcium sulfate dihydrate, CaSO 4∙2H2O) thermally degrade into calcium sulfate anhydrite (CaSO 4) via an intermediate calcium sulfate hemihydrate (CaSO 4∙ ½H2 O, bassanite) phase. Microstructural and mineralogical differences were observed when temperature treated gypsums from different origins were compared. The detailed knowledge of gypsum powder properties at different temperature regime is important parameter for the assurance of 3D printing key parameters such as flowability, roughness and wettability, especially for determination of saturation levels and setting time. After all, these parameters define final mechanical properties of 3D printed structures. By using such approach, the understanding of material compatibility for 3D printing technology can be defined and improved if necessary. Keywords: 3D print, additive manufacturing, gypsum, temperature Published in DiRROS: 25.01.2024; Views: 430; Downloads: 258
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4. 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, dictionary, encyclopaedia, lexicon, manual, atlas, map Abstract: 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. Keywords: gradbeni proizvodi, ponovna uporaba, ekonomski vidik, industrija cementa, krožno gospodarstvo, industrijski odpadki, zakonodaja, elektronske knjige Published in DiRROS: 22.01.2024; Views: 447; Downloads: 219
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5. Production of lightweight alkali activated mortars using mineral woolsAhmad Alzaza, Mohammad Mastali, Paivo Kinnunen, Lidija Korat, Zahra Abdollahnejad, Vilma Ducman, Mirja Illikainen, 2019, original scientific article Abstract: This experimental study aimed to develop a fiber-reinforced lightweight mineral wool-based alkali activated mortar. The lightweight mineral wool-based alkali activated mortars were produced using premade foam and reinforced by polypropylene (PP) fibers. They were assessed in terms of fresh and hardened-state properties. Fresh-state properties were investigated by mini-slump tests. Hardened-state characteristics were assessed by ultrasonic pulse velocity, dry density, compressive and flexural strengths, drying shrinkage, efflorescence, water absorption, and permeable porosity. For the first time, the resistance of the synthesized lightweight mineral wool-based alkali activated mortars against harsh conditions (carbonation, freeze and thaw, and high temperature) were evaluated. The porous structures of the developed lightweight alkali activated mortars were also analyzed using an X-ray micro-computed tomography (CT) technique. Lightweight mix compositions with densities in a range of 770%1510 kg/m3, compressive strengths of 1%9 MPa, and flexural strengths of 2.6%8 MPa were developed. Increases in both density and strength after carbonation were also recorded, while a decrease of strength was noticed after exposure to freeze/thaw and high temperatures of up to 500 %C. Keywords: alkali activation, mineral wool, mortars Published in DiRROS: 24.10.2023; Views: 512; Downloads: 216
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6. Impacts of casting scales and harsh conditions on the thermal, acoustic, and mechanical properties of indoor acoustic panels made with fiber-reinforced alkali-activated slag foam concretesMohammad Mastali, Paivo Kinnunen, Marjaana Karhu, Zahra Abdollahnejad, Lidija Korat, Vilma Ducman, Ahmad Alzaza, Mirja Illikainen, 2019, original scientific article Abstract: This paper presents experimental results regarding the efficiency of using acoustic panels made with fiber-reinforced alkali-activated slag foam concrete containing lightweight recycled aggregates produced by using Petrit-T (tunnel kiln slag). In the first stage, 72 acoustic panels with dimension 500 % 500 % 35 mm were cast and prepared. The mechanical properties of the panels were then assessed in terms of their compressive and flexural strengths. Moreover, the durability properties of acoustic panels were studied using harsh conditions (freeze/thaw and carbonation tests). The efficiency of the lightweight panels was also assessed in terms of thermal properties. In the second stage, 50 acoustic panels were used to cover the floor area in a reverberation room. The acoustic absorption in diffuse field conditions was measured, and the interrupted random noise source method was used to record the sound pressure decay rate over time. Moreover, the acoustic properties of the panels were separately assessed by impedance tubes and airflow resistivity measurements. The recorded results from these two sound absorption evaluations were compared. Additionally, a comparative study was presented on the results of impedance tube measurements to compare the influence of casting volumes (large and small scales) on the sound absorption of the acoustic panels. In the last stage, a comparative study was implemented to clarify the effects of harsh conditions on the sound absorption of the acoustic panels. The results showed that casting scale had great impacts on the mechanical and physical properties. Additionally, it was revealed that harsh conditions improved the sound properties of acoustic panels due to their effects on the porous structure of materials. Keywords: alkali activation, slag, acoustic panels Published in DiRROS: 15.09.2023; Views: 448; Downloads: 241
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7. Characterization of fly ash alkali activated foams obtained using sodium perborate monohydrate as a foaming agent at room and elevated temperaturesLidija Korat, Vilma Ducman, 2020, original scientific article Abstract: Alkali activated foams have been extensively studied in recent years, due to their high performance and low environmental footprint compared to foams produced via other methods. Three types of fly ash differing in chemical and mineralogical composition and specific surface were used to synthesize alkali activated foams. Sodium perborate monohydrate was added as a foaming agent and sodium dodecyl sulphate as a stabilizing agent. Foams were characterized at room temperature and after exposure to an elevated temperature (1,000 °C). Densities from 1.2 down to 0.3 g/cm 3 were obtained, depending on the type of fly ash and quantity of foaming agent added. Correspondingly, compressive strength ranged from 1 to 6 MPa. Comparing all three fly ashes the most favorable results, in terms of density and corresponding compressive strength, were achieved from the fly ash with the highest amounts of SiO 2 and Al2 O 3 , as well as the highest amorphous phase content i.e., RI fly ash. Furthermore, after firing to 1,000 °C, the density of samples prepared using fly ash RI remained approximately the same, while the compressive strength increased on average by 50%. In the other two types of fly ash the density increased slightly after firing, due to significant shrinkage, and compressive strength increased by as much as 800%. X-ray powder diffraction analysis confirmed the occurrence of a crystallization process after firing to 1,000 ° C, which resulted in newly formed crystal phases, including nepheline, sodalite, tridymite, and gehlenite. Keywords: foamed alkali activated materials, geopolymers, properties, micro-CT Published in DiRROS: 22.08.2023; Views: 446; Downloads: 274
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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, original scientific article Abstract: 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. Keywords: klinker, belit-sulfoaluminat, razvoj por, sintranje Published in DiRROS: 04.08.2023; Views: 565; Downloads: 243
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9. 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: 550; Downloads: 439
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