1. Dataset for the article Sequestration capacity of bio-based ashes and influence of carbonation on the leaching behavior depending on their mineralogical compositionSara Tominc, Majda Pavlin, Lea Žibret, Vilma Ducman, Ottosen Lisbeth M., 2025, complete scientific database of research data Abstract: The dataset supports the data presented in the tables and figures of the scientific article Sequestration capacity of bio-based ashes and influence of carbonation on the leaching behavior depending on their mineralogical composition (doi: 10.1016/j.ceramint.2025.11.229). It includes calcimetric measurements, XRF, TGA, and XRD analysis data, as well as calculations of CO2 uptake and CO2 sequestration capacity for the analyzed samples. Additionally, it contains original FTIR measurement data, which are not included in the article and serve as supplementary material.
Keywords: enforced carbonation, maximum sequestration capacity, leaching, heavy metals, mineralogy, bio-based ash
Published in DiRROS: 21.10.2025; Views: 124; Downloads: 35
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2. Enhancing densification of metakaolin-based geopolymers via the cold sintering processAbdullah Jabr, Srečo D. Škapin, Sara Tominc, Nina Daneu, Jakob Koenig, Vilma Ducman, Lidija Korat Bensa, Raúl Bermejo, Matjaž Spreitzer, 2025, original scientific article Abstract: Clay-based materials typically require high-temperature processing (>900 ◦C), resulting in high energy consumption. This study explores cold sintering of metakaolin (MK) powders to achieve high mechanical strength at significantly lower processing temperatures. By applying uniaxial pressure of 400 MPa and heating to only 240 ◦ C in the presence of 15 mol/L NaOH solution, successful densification of structurally sound and dense samples with an average density of 2.16 g/cm³ and a biaxial flexural strength of ~35 MPa was achieved. This strength surpasses that of conventionally sintered MK (1470 ◦C) by ~30 %. Densification was found to be governed by synergistic mechanisms involving MK exfoliation, conformal sintering around aggregates, and the precipitation of an amorphous sodium aluminosilicate hydrate phase. Crack formation was avoided through process optimization and verified using X-ray micro-computed tomography. These findings offer new insights into the chemo- mechanical mechanisms of cold sintering and demonstrate its potential as an efficient route for producing structural materials.
Keywords: cold sintering, metakaolin, geopolymer, delaminations, exfoliation
Published in DiRROS: 15.10.2025; Views: 198; Downloads: 88
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3. Comparing methods for determining the CO2 content in CO2-Sequestering materials and natural rockNika Kavčič, Sara Tominc, Lea Žibret, Gorazd Žibret, Mitja Kolar, Vilma Ducman, 2025, original scientific article Abstract: Carbon capture plays an important role in the decarbonation of the building sector. One way to capture carbon is through mineral carbonation, in which Ca and Mg compounds react with CO2 to form stable carbonate minerals such as calcite, dolomite, magnesite and/or siderite, permanently sequestering CO2. Various techniques are available to measure the amount of permanently bound CO2 and quantify the carbonation potential. The suitability and accuracy of a particular method are very important, as the accurate determination of CO2 is crucial to correctly assess the sequestration potential of different materials. This study compares the three methods: calcimetric, gravimetric and thermogravimetric analysis used for CO2 determination in different types of ash, slag and natural rock. While the CO2 content in natural rock is stable, the CO2 content in slag and ash can change over time as the contained minerals gradually absorb CO2 (by natural or accelerated carbonation) until they are fully carbonated. To avoid errors in testing the CO2 uptake, as-received samples were first exposed to the full carbonation process and then tested. The comparison of calcimeter, thermogravimetric and gravimetric analysis of ground and sieved samples with a particle size below 125 μm shows that the results usually differ by less than 2 %. Higher deviations could be caused by non-carbonate minerals (especially in slags) that can react with hydrochloric acid during the calcimetric and gravimetric tests and/or decompose in the range where carbonates decompose, contributing to inaccurate CO2 measurements. The measurement uncertainty was calculated for all three quantitative methods to allow a practical comparability.
Keywords: CO2 sequestration, ash, slags, natural rocks, TGA, calcimetry, measurement uncertainty
Published in DiRROS: 15.10.2025; Views: 199; Downloads: 104
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4. Characterization of the substrates from two cultural-heritage sites and a preparation of model substratesSabina Dolenec, Vilma Ducman, Snezana B. Vučetić, Edo Velkavrh, Miroslava Radeka, Jonjaua Ranogajec, 2014, original scientific article Abstract: In this study the microstructural characteristics of the materials selected from two cultural-heritage sites (the Dornava Manor, Slovenia, and the Bač Fortress, Serbia) and of the model samples - the control and aged ones - were investigated. The samples were characterized by means of mercury intrusion porosimetry (MIP) and total-specific-area analysis (BET). A good agreement was achieved between the samples of the brick and mortar from the Bač Fortress,or the samples of the natural stone and render from the Dornava Manor, and the corresponding model samples.
Keywords: materials, microstructure, brick, natural stone, mortar, frost resistance
Published in DiRROS: 26.09.2025; Views: 250; Downloads: 101
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5. Characteristics of lightweight aggregate concrete interfacial transition zoneVesna Milovanović, Vilma Ducman, Miroslava Radeka, 2014, original scientific article Abstract: The paper presents the characteristics of the interfacial zone between the lightweight aggregate produced on the basis of waste materials and binder matrix with the application of the methods SEM, EDS and the Vickers micro hardness test. On the basis of the SEM and EDS analysis, as well as the criteria for the atomic ratio of elements which compose some products of hydration, we can gain insight into the dominant composition of the interfacial zone. The values of the Vickers micro hardness test for four kinds of tested concrete after seven days of hydration is impossible to correlate with the composition of the interfacial zone in reliable way, whereas after twenty eight days the differences in values are insignificant.
Keywords: lightweight aggregate, waste material, interfacial zone
Published in DiRROS: 26.09.2025; Views: 183; Downloads: 87
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6. Mechanical and microstructural characterization of geopolymer synthesized from low calcium fly ashSabina Dolenec, Vilma Ducman, 2015, original scientific article Abstract: This study deals with the mechanical and microstructural characterization of geopolymers synthesized from locally available fly ash. A low calcium fly ash was activated using a sodium silicate solution. Samples were characterized by means of flexural and compressive tests, Fourier Transform Infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy(SEM). Porosity and pore size distributions were identified using mercury intrusion porosimetry and gas sorption. The compressive strength of the produced geopolymers, which is in the range of 1.6 to 53.3 N/mm2, is strongly related to the water content as well as SiO2/Na2O mass ratio of an alkali activator. The compressive strength significantly increased with decreases in the water content and increased silicon concentration used for the synthesis of geopolymers.
Keywords: geopolymers, fly ash, microstructure, mechanical properties
Published in DiRROS: 05.09.2025; Views: 323; Downloads: 177
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7. Municipal solid waste incineration (MSWI) bottom ash-blended cementitious materials : performance, challenges, and potential solutionsBoyu Chen, Priyadharshini Perumal, Chen Liu, Yun Chen, Cheng Chang, Majda Pavlin, Davor Kvočka, Vilma Ducman, Tero Luukkonen, Mirja Illikainen, Guang Ye, 2025, review article Abstract: The recycling of municipal solid waste incineration (MSWI) bottom ash as a supplementary cementitious material (SCM) has attracted global attention, driven by the increasing availability of this by-product and the demand for sustainable SCMs to lower CO2 emissions from cement production. Currently, the widespread use of MSWI bottom ash in the cement industry is hindered by the lack of guidelines to regulate material composition, optimize pretreatment processes, and specify mix design requirements. This review compiles and analyzes literature data on mix design, microstructural evolution, fresh properties, mechanical properties, durability, leaching risks, and environmental impacts of MSWI bottom ash-blended cement pastes, mortars, and concretes. The analysis aims to assess the influence of the pretreatment and physicochemical properties of bottom ash on the microstructure and performance of blended cementitious materials. The Ash Impact Strength Index (AISI) is introduced to quantify the effects of various factors on compressive strength, enabling direct comparison across different studies. Based on the statistical analysis of the 28-day AISI, the key quality requirements for MSWI bottom ash as an SCM are proposed, along with the optimal mix design. This work provides valuable insights and practical guidance to support the integration of bottom ash into the cement industry.
Keywords: ash, ash-blended cementitious materials, performance
Published in DiRROS: 29.08.2025; Views: 399; Downloads: 260
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8. Carbonation of lightweight alkali-activated aggregates based on biomass fly ash : effect on microstructure and leaching behaviorAnže Tesovnik, Ottosen Lisbeth M., Vilma Ducman, 2025, original scientific article Abstract: Artificial aggregates offer a sustainable solution to large-scale waste utilization and the increasing demand for limited natural aggregates. This study extends the understanding of the production of artificial lightweight aggregates with a variable rotation speed approach based solely on biomass fly ash (BFA) alkali-activated materials (AAMs). Systematic variation of alkali content and solution density at a constant water-to-solids ratio showed that alkali concentration significantly influences granulation beyond what can be explained by water availability. The interplay between alkali activation and carbonation was investigated using different mix designs and curing conditions, as well as comparing simultaneous curing carbonation with post-cure carbonation. The results were evaluated with regard to the effects on the macro- and microstructural properties as well as on the leaching behavior. Prolonged carbonation initiated after aggregate formation resulted in premature depletion of Ca, limiting the development of C-A-S-H gels and increasing microporosity, leading to a reduction in mechanical properties. In contrast, post-curing carbonation maintained a compressive strength of over 1 MPa while still allowing carbonation benefits, resulting in compressive strengths comparable to lightweight expanded clay aggregates. Carbonation also proved to be an effective leaching mitigation strategy by stabilizing heavy metals through both physical encapsulation and chemical pH regulation. These results underline the importance of carbonation timing in high Ca AAMs and highlight lightweight aggregates as a viable pathway for BFA valorization, CO₂ sequestration and sustainable construction applications. This approach offers an alternative valorization strategy for BFA facing regulatory restrictions for direct use in cement, while contributing to carbon capture and circular economy initiatives.
Keywords: artificial aggregates, lightweight aggregates, biomass ash, alkali-activated materials, leaching, carbonation
Published in DiRROS: 18.07.2025; Views: 448; Downloads: 461
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9. Selective seperation of magnesium from Slovenian dolomitesJernej Imperl, Mitja Kolar, Vilma Ducman, Gorazd Žibret, Lea Žibret, 2025, published scientific conference contribution Abstract: Although magnesium is one of the most abundant elements on Earth by weight, the demand for magnesium is constantly increasing due to its widespread use in a diverse range of industries such as metal alloys, electronics, batteries, agricultural and pharmaceutical compounds. For this reason, magnesium is categorised as a critical raw material by the European Union. Dolomite CaMg(CO3)2 is one of the most important mineral sources of magnesium, which in its pure form contains 13.18 % magnesium by weight. Various pyrometallurgical and hydrometallurgical processes have been developed and are used to extract magnesium from dolomite and other magnesium ores. In this study, samples of dolomite of different geological ages were collected in Slovenia and their elemental composition was analysed by microwave-assisted acid digestion and ICP-OES. Magnesium was then extracted by selective leaching and selective precipitation. Leaching was carried out with inorganic and organic acids. The separation of magnesium and calcium in a solution prepared by dissolving dolomite with acid was carried out by precipitation with hydroxide and oxalate. High extraction yields of magnesium and a significant separation between the two metals were achieved with both methods.
Keywords: magnesium, dolomite, extraction, selective leaching, selective precipitation
Published in DiRROS: 16.07.2025; Views: 406; Downloads: 235
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10. Dataset for the article Comparing methods for determining the CO2 content in CO2-Sequestering materials and natural rockSara Tominc, Nika Kavčič, Lea Žibret, Gorazd Žibret, Mitja Kolar, Vilma Ducman, 2025, complete scientific database of research data Abstract: The dataset supports the data in the tables and figures of the scientific article Comparing methods for determining the CO2 content in CO2-Sequestering materials and natural rock (doi: https://doi.org/10.1016/j.ceramint.2025.07.109). It contains the calcimetric measurements, the original results of the XRF measurements and the original data of the TGA, gravimetric and XRD analyzes as well as the calculations of the measurement uncertainty for the calcimetric, gravimetric and TG analyzes.
Keywords: sekvestracija CO2, pepel, žlindre, naravni kamen, TGA, kalcimetrija, merilna negotovost, CO2 sequestration, ash, slags, natural rocks, TGA, calcimetry, measurement uncertainty
Published in DiRROS: 24.06.2025; Views: 471; Downloads: 217
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