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Povzetek: The European Union’s shift towards a circular economy emphasizes the substitution of virgin materials with recycled alternatives, particularly in the construction sector, which can accommodate large volumes of industrial by-products. Ashes from coal, biomass, paper sludge, and co-combustion processes are abundant secondary materials whose variable chemical and mineralogical compositions necessitate careful assessment to enable safe and effective reuse.This study investigates the hydration behaviour and early carbonation potential of ashes of different origin. The ashes were characterized using X-ray fluorescence, X-ray diffraction, and scanning electron microscopy coupled with energy-dispersive spectroscopy. Hydraulic reactivity was evaluated by preparing ash pastes at a 1:1 water-to-ash ratio and monitoring hydration product formation over time using XRD. Carbonation of co-combustion ash was studied under controlled CO₂ conditions (2 % CO₂, 50 % RH, 20 °C ± 1 °C) at different moisture contents (0 wt.%, 10 wt.%, 20 wt.%, and 40 wt.%) and early curing times (0 hours, 1 hours, 4 hours, and 24 hours).Results indicate distinct differences among the ashes. Paper sludge ash exhibited the most extensive formation of calcium aluminate hydrates, coal and co-combustion ashes showed moderate hydration, while biomass ash produced only minor secondary phases. Carbonation of co-combustion ash proceeded concurrently with hydration, with lime depletion and calcite formation enhanced by higher moisture and longer curing. These coupled processes influenced both the kinetics and composition of hydration products. The findings demonstrate the potential of diverse combustion ashes for valorisation in construction materials and provide insight into their reactivity under early-age hydration and carbonation conditions, supporting circular economy initiatives.
Ključne besede: circular economy, ashes from combustion, hydraulic activity, carbonation, phase composition, amorphous phase
Objavljeno v DiRROS: 14.01.2026; Ogledov: 169; Prenosov: 93
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Objavljeno v DiRROS: 14.05.2025; Ogledov: 614; Prenosov: 184
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Povzetek: Research in the field of sensing has focused on tailoring the responsiveness of materials through the variation in materials properties achieved via functionalization of the mesoporous matrix. pH indicator dyes capable of protonation/deprotonation reactions are known to display different forms, resulting in changes in colour. This research focused on the preparation of mesoporous substrates SBA-15 with integrated pH indicator dye o-cresolsulphonephtalein (cresol red) grafted with (3-aminopropy) trimethoxysilane (gaining functionalized-SBA-15 material) in order to gain a colour change response following release of the dye. UV-Vis reflectance and absorbance spectra were used to evaluate forms of cresol red. The textural properties, including specific surface area, pore size distribution and pore volume were evaluated using nitrogen sorption, and XRD analysis was conducted to evaluate crystallinity of the material and pore ordering. The presence of 3-aminopropyl groups was determined by thermal decomposition using TGA–DSC/MS. The functionalized SBA-15 materials loaded with cresol red mostly retained ordering of the pores and showed a slight reduction in surface area. Functionalization changed the surface properties of the material. In the non-functionalized SBA-15, cresol red was present in both double (H2L) and single (HL−) protonated forms, whereas in the functionalized SBA-15 the deprotonated L2−form prevailed. Through desorption experiments cresol red was successfully desorbed from selected sample to different media. The change of colour caused by alterations in the form of the dye once released from the mesoporous silica material into the medium was confirmed. The form of cresol red released was determined by the pH of the medium.
Ključne besede: mezoporozni materiali, SBA-15, funkcionalizacija, uravnavanje odzivnosti, zaznavanje
Objavljeno v DiRROS: 13.02.2024; Ogledov: 1357; Prenosov: 1071
Celotno besedilo (10,52 MB)
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Povzetek: The importance of thermal modification is increasing worldwide. Increased use of thermally modified timber (TMT) has resulted in a need for reliable quality control, comprising control of variation of the production within defined limits, allowing third-party control in the case of certification and the regulation of customer complaints and claims. Techniques are thus needed to characterise the modification of quality in terms of improved target properties of TMT during industrial production, and of TMT products that have been in service for an arbitrary time. In this study, we aimed to utilise dynamic vapor sorption (DVS) for this purpose. Norway spruce (Picea abies) and European beech (Fagus sylvatica) samples were thermally modified at different temperatures according to different heat treatment techniques: (1) the Silvapro process based on an initial vacuum; (2) an air heat treatment, whereby samples were wrapped in aluminium foil; (3) thermal modification of wood samples in the ambient atmosphere in a laboratory oven. Wood samples from closed processes were analysed for validation. TMT was characterised with respect to mass loss, colour and density. Mass loss of wood due to modification (MLTM) was correlated with factors derived from DVS analysis. The present DVS measurements suggest that the equilibrium wood moisture content (EMC95% RH), the time to reach 10% wood moisture content (t10% MC), and the elongation factor, c, derived from a logarithmic function, can serve as alternative parameters to characterise the quality of several thermal modification processes. Further studies are recommended using other wood species, different modification processes and further parameters gained from DVS measurements to understand the robustness and the predictive power of the applied technique
Ključne besede: thermal modification, quality control, dynamic vapour sorption, wood, moisture content
Objavljeno v DiRROS: 31.08.2023; Ogledov: 1471; Prenosov: 923
Celotno besedilo (1,91 MB)
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Povzetek: Hybrid phenol-formaldehyde (PF) resins represent one of the most important niche groups of binding systems for composites. New industrial needs, environmental requirements, and price fluctuations have led to further research on materials with enhanced mechanical and thermal properties. The preparation of novel hybrid materials can be achieved by inclusion of various elements or functional groups in the organic polymer phenolic framework. Herein, we report the synthesis and characterization of a PF-based hybrid material with different nanoscale silicone species and ZnAl-layered double hydroxide (LDH). The main goals of this study were to improve the synthetic pathways of hybrid resin, as well as to prepare granulated composite materials and test samples and determine their characterization. Added inorganic species increased the glass-transition temperature by a minimum of 8 °C, which was determined using differential scanning calorimetry (DSC). Rheological properties (melting viscosity and flow distance) of the hybrid resin were measured. The homogeneity of distribution of added species across the organic matrix was evaluated with scanning electron microscopy (SEM). With synthesized new hybrid-binding systems, we prepared different granulated composite materials and evaluated them with the measurements of rheological properties (flow curing characteristics). Tensile strength of samples, prepared from granulated composite material, improved by more than 5%.
Ključne besede: phenol-formaldehyde hybrid resins, nano-SiO2, ZnAl-LDH, composites, glass-transition temperature, mechanical properties
Objavljeno v DiRROS: 03.05.2023; Ogledov: 1421; Prenosov: 899
Celotno besedilo (1,92 MB)
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