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Povzetek: The study investigates the optimisation of fly ash (FA) pretreatment for producing alkali-activated materials (AAMs) with high mechanical strength and reduced radioactive content. Three FA conditions were compared: as-received, sieved below 200 μm, and treated thermally at 550 °C. Both the sieving and thermal treatment removed the residual cellulose effectively, enhancing the compressive strength significantly, while the microwave irradiation improved the strength only in the as-received FA containing organic content. Sieving below 200 μm also reduced the detectable radionuclides, providing a simple, energy-efficient and low-carbon approach to synthesising high-performance, radwaste-safe AAMs. The preliminary results highlight sieving as a promising method to produce environmentally sustainable construction materials from radioactive FA.
Ključne besede: alkali-activated materials, radioactive fly ash, naturally occurring radioactive material, radionuclide separation, microwave irradiation, circular economy
Objavljeno v DiRROS: 15.05.2026; Ogledov: 106; Prenosov: 72
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Povzetek: The increasing demand for lightweight construction materials and the depletion of natural aggregates highlight the need for circular solutions based on industrial residues. Co-incineration biomass ash (BA), despite its high availability, carbon content, and variable composition, remains underutilised in high-value applications. This study explores a previously unexamined valorisation route through the production of sintered alkali-activated aggregates using sodium-silicate-assisted pre-treatment. Two BA mixes with different Na2O dosages (7.57 and 5.44 wt% Na2O) were pelletized and thermally treated between 700 and 1200 ◦C. The alkali activation pretreatment simultaneously improved the granulation efficiency, enabled the formation of alkali-activated gel, and supplied Na2O as a flux, significantly influencing the crystalization, melting, and sintering behavior. Comprehensive characterisation using mercury intrusion porosimetry, dilatometry, X-ray diffraction, Fouriertransform infrared spectroscopy, thermogravimetry–differential thermal analysis, and scanning electron microscopy revealed a coherent thermal sequence: from gel deterioration and a macroporosity development below 800 ◦C, to the crystallization of Ca–Mg silicates and the formation of an akermanite-dominated matrix at 800–1000 ◦C, followed by partial melting and sintering in the presence of a liquid phase above 1000 ◦C. A higher alkali content promoted earlier densification and strength development. Aggregates with higher Na2O content (BA1) exhibited an earlier onset and higher intensity of sintering shrinkage, reaching a compressive strength of 4.53 MPa at 1100 ◦C, corresponding to more than a fourfold increase compared to thermally untreated aggregates, whereas the lower-alkali mix (BA2) remained below 0.26 MPa at the same temperature. Open porosity of BA1 aggregates increased to 78.8% after heating to 800 ◦C due to deterioration of the alkali-activated gel, followed by densification accompanied by akermanite-dominated crystallization and pore coalescence, resulting in 73.1% porosity and a bulk density of 1.28 g/cm3 at 1100 ◦C. The results identify BA as a promising precursor for lightweight or dense SAA and demonstrate alkali-activation-assisted thermal treatment to be a technically applicable circular-economy pathway for converting co-incineration BA into value-added construction materials.
Ključne besede: alkali-activated materials, biomass ash, sintered aggregates, lightweight aggregates
Objavljeno v DiRROS: 06.05.2026; Ogledov: 105; Prenosov: 119
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Povzetek: The Geological Survey of Slovenia (GeoZS), with the assistance of the ENALOS Research and Development (ENALOS), the Slovenian National Building and Civil Engineering Institute (ZAG) and the Katholieke Universiteit Leuven (KUL), has compiled a report documenting the demonstration and application phase of the project. This report contains a technical analysis on the materials produced as well as an economic analysis, and thus more accurately calculates the financial benefits of the technology.
Ključne besede: odpadni materiali, waste materials, alkalijsko aktivirani materiali, alkali activated material, trajnostni pristop, sustainable approach, jeklarska žlindra, steel slag, rdeče blato, red mud
Objavljeno v DiRROS: 15.01.2026; Ogledov: 530; Prenosov: 0
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Povzetek: The dataset contains measurements of thermally treated and non-thermally treated alkali-activated aggregates produced from co-incineration biomass ash. It includes data on ash characterization, mechanical performance, thermal behavior, microstructural properties, and the chemical and mineralogical composition of the produced aggregates. This dataset supports the findings presented in the article "Effect of alkali-activation pre-treatment of sintered aggregates from biomass fly ash on microstructural and mineralogical evolution" (https://doi.org/10.1016/j.ceramint.2026.03.041).
Ključne besede: alkali-activated materials, sintering, lightweight aggregates, thermal treatment
Objavljeno v DiRROS: 24.11.2025; Ogledov: 380; Prenosov: 220
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Povzetek: 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.
Ključne besede: artificial aggregates, lightweight aggregates, biomass ash, alkali-activated materials, leaching, carbonation
Objavljeno v DiRROS: 18.07.2025; Ogledov: 874; Prenosov: 841
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