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Abstract: Mineral CO2 sequestration is a promising approach for reducing greenhouse gas emissions by storing CO2 in stable forms permanently. This process involves capturing CO2 and converting it into solid carbonates through mineralisation. Waste ashes and slags, by-products of waste incineration and steel production, are promising materials for CO2 sequestration, due to their high alkalinity and reactive mineral phases. In this study, the CO2 sequestration potentials of different metallurgical slags and incineration ashes from Austria and Slovenia were analysed using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and calcimetry. Biomass ash (A1) showed the highest sequestration capacity of 153.7 g CO2 per kg of ash.
Keywords: CO2 sequestration capacity, enhanced carbonation, thermogravimetric analysis, calcimetry, Fourier transform infrared spectroscopy
Published in DiRROS: 15.05.2026; Views: 475; Downloads: 388
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Abstract: 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.
Keywords: circular economy, ashes from combustion, hydraulic activity, carbonation, phase composition, amorphous phase
Published in DiRROS: 14.01.2026; Views: 576; Downloads: 384
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Abstract: The dataset supports the data presented in the tables and figures of the conference paper "Mineral CO2 sequestration in industrial waste materials: a comparative study using FTIR, TGA and calcimetry" (https://doi.org/10.18690/um.fkkt.1.2026.8). It includes masses before and after carbonation treatment, calcimetric measurements, XRF, TGA, FTIR and XRD analysis data, as well as calculations of CO2 uptake and CO2 sequestration capacity for the analysed samples.
Keywords: alkali-activated materials, biomass ash, carbonation, artificial aggregates, alkalijsko aktivirani materiali, biomasni pepel, karbonatizacija, umetni aggregati
Published in DiRROS: 04.12.2025; Views: 544; Downloads: 200
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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: 1193; Downloads: 1204
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Abstract: There are several ways to utilize as-received or pre-treated waste ash, one of the most promising is by accelerated mineral carbonation. Ashes with a high content of Ca and Mg compounds, such as ashes from wood biomass, are ideal candidates for sequestration. Due to the shift toward renewable fuels, ash from biomass as a by-product of solid fuel combustion is therefore available in huge quantities. As part of the EU AshCycle project, we have analyzed ashes from different incineration and thermal power plants to determine their carbon sequestration potential. These include various waste ashes from Slovenia, which were subjected to accelerated carbonation in a closed carbonation chamber with a CO2 concentration of 4% (v/v), 80% relative humidity and a temperature of 40 °C until maximum CO2 uptake was reached. CO2 quantification was performed using calcimetry (pressure calcimeter) and thermogravimetry. We have shown that ash from wood biomass and the co-combustion of wood waste and paper sludge have a high CO2 sequestration potential in comparison to others. The direct use of wood biomass ash for CO2 sequestration in carbonated building products could significantly benefit the circular economy, especially since 70% of wood biomass ash is still landfilled.
Keywords: CO2 sequestration capacity, accelerated carbonation, waste ashes, thermogravimetric analysis, calcimetry
Published in DiRROS: 07.04.2025; Views: 1322; Downloads: 938
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