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Povzetek: With the trend towards renewable alternatives to fossil fuel sources, further uses of biomass and waste ash instead of landfilling are being explored. This study investigates the potential of fly and bottom ashes from burning wood (alone or with coal), as well as coal-co-combustion of municipal solid waste, sewage sludge, and paper sludge, for use in extruded fired bricks fired at 950 °C. The influence of ash content (0 to 15 wt% ash) and ash type (10 wt% ash) on the physical, mechanical, and microstructural properties of the fired bricks was studied. The compressive strength of the reference sample without ash was 72.6 MPa and decreased gradually with an increasing ash content. Open porosity ranged from 28% (reference, no ash) to 43% (15 wt% ash), and water absorption from 12% to 28%, reflecting the pore-forming role of the added ashes. All samples had a compressive strength above the 10 MPa limit specified in EN 772-1, except for bricks with 5 wt% paper sludge bottom ash (B4, W-PS BA). The leaching concentrations indicate that heavy metals were effectively immobilised within the ceramic structure of the fired bricks, relative to inert and non-hazardous waste limit values under EN 12457-2 test conditions. These results suggest that 5% substitution of primary raw materials with ashes may contribute to the production of bricks with reduced environmental impact and improved resource efficiency. The study provides a basis for further formulation of extruded bricks with biomass and waste-derived ashes.
Ključne besede: biomass and waste derived ashes, clay, extruded fired bricks, ceramic-technological tests, microstructure, leaching
Objavljeno v DiRROS: 15.06.2026; Ogledov: 304; Prenosov: 371
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Povzetek: This study presents the in-situ synthesis of hydroxyapatite (HAp) within the structure of beech and pine wood. The modification process utilized a two-step vacuum-pressure impregnation coupled with chemical precipitation using calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions, followed by exposure to ammonium hydroxide vapors. While the initial focus was on the overall physicochemical changes, microstructural characteristics and fire behavior of the mineralized wood, the main aim is to specifically investigate the effects of leaching. Because HAp synthesis produces water-soluble ammonium nitrate (NH4NO3) as a by-product, this research systematically addresses how the removal of this component affects the final properties of wood. HAp formation was confirmed by FTIR and X-ray diffraction, while scanning electron microscopy and microcomputed tomography revealed HAp deposits primarily in the cell lumen of both wood species. Fire behavior was evaluated using thermal analysis and the cone calorimeter. The incorporation of non-flammable HAp synthesized within the wood structure may act as a barrier and mass transfer during pyrolysis. This results to comparable or slightly enhanced key fire performance parameters when comparing leached HAp synthesized samples with leached reference samples. In contrast, the unleached HAp synthesized samples, which still contained residual NH4NO3, showed deterioration in fire growth rate (FIGRA) and heat release rate (HRR) parameters, confirming that NH4NO3 acts as an oxidant. However, this oxidative property also leads to improvements in total heat release (THR) and total smoke production (TSP) parameters compared to unleached references, representing a complex interaction when studying the fire properties of mineralized wood.
Ključne besede: chemical precipitation method, fire retardancy, hydroxyapatite, HAp, leaching process, wood
Objavljeno v DiRROS: 17.04.2026; Ogledov: 443; Prenosov: 446
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Povzetek: The dataset supports the data presented in the tables and figures of the conference paper: "Fiber-reinforced cement as a source of microplastics and their post-release behaviour" (doi: https://doi.org/10.18690/um.fkkt.1.2026.9). It includes mass measurements and calculations used for density determination of (micro)fibres by pycnometer, quantitative results derived from image analysis performed using a custom-made Mathematica program for assessing cement coverage on fibre surfaces, as well as results of leaching experiments, including measured TOC, IC and TC concentrations in leachate samples.
Ključne besede: mikroplastika, vlakno-armirani cement, gradbeni materiali, meritve gostote, ekperiment izluževanja, adhezija ostankov cementa, microplastics, fibre-reinforced cement, construction materials, density measurement, leaching experiment, adhesion of cement residues
Objavljeno v DiRROS: 06.01.2026; Ogledov: 424; Prenosov: 331
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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: 1195; Prenosov: 1210
Celotno besedilo (7,95 MB)
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Povzetek: There is an increasing tendency to replace conventional agricultural plastic mulching films with biodegradable alternatives. However, while the latter biodegrade well under controlled conditions (e.g. industrial compost), their biodegradation in non-target environments (e.g. aquatic environments) is questioned and poorly understood. Therefore, in this study, microplastics derived from conventional polyethylene (PE) and biodegradable polybutylene adipate terephthalate starch blend (PBAT) mulching films were exposed to UV irradiation and subsequently tested for their ready biodegradability in an aqueous medium where changes in their characteristics were evaluated. The results showed limited biodegradation for pristine and UV-aged PE: no morphological, surface chemical or internal changes were observed. Pristine PBAT showed signs of initial biodegradation, while UV-aged PBAT biodegraded by up to 57%. New functional groups appeared on the PBAT surface after UV irradiation according to FTIR analysis and crystallinity increased after biodegradation. Elemental analysis revealed a range of metals in PE and PBAT microplastics. No changes in metal distribution analysed in microplastic after UV-aging or biodegradation were found, except that less titanium was present in PBAT after biodegradation indicating potential leaching. None of the PBAT microplastics had ecotoxic effects towards the aquatic plant Lemna minor. Pristine and UV-aged PE showed negative effects on roots, but these were not observed after biodegradation. Low biodegradation of pristine PBAT and possible leaching of metals demonstrated here raise questions about the sustainable use of biodegradable alternatives, especially when they enter non-target environments.
Ključne besede: microplastics, biodegradable plastics, aging, biodegradation, ecotoxicity, leaching
Objavljeno v DiRROS: 27.05.2025; Ogledov: 1157; Prenosov: 1135
Celotno besedilo (6,56 MB)
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