PSI - Issue 67

Davide di Summa et al. / Procedia Structural Integrity 67 (2025) 53–60 Davide di Summa/ Structural Integrity Procedia 00 (2024) 000 – 000

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rises to 13% and 32%, respectively. This is largely due to the energy-intensive production and refining of aluminium oxide, which involves electrolytic refining of alumina from bauxite ore. This process demands considerable energy, often derived from fossil fuels, which release greenhouse gases like carbon dioxide (CO 2 ) and methane (CH 4 ) into the atmosphere. These gases contribute to global warming and indirectly affect the ozone layer by altering atmospheric dynamics (Sáez-Guinoa et al., 2024). Regarding the UHPC mix design incorporating alumina nano-fibrse, cement and steel fibres continue to be the primary contributors to environmental impacts, with cement reaching peaks of up to 53% in terms of global warming potential, while steel fibres account for as much as 45% in the case of eutrophication. It is worth emphasizing that, despite their inclusion in the mix, the contribution of alumina nano-fibres remains relatively minor, with their impact not exceeding 2% across all assessed categories.. These insights highlight areas for potential improvement in the production processes of both alumina nanofibers and UHPC with alumina nanofibers. Specifically, with regard to the first one, due to the high incidence of electricity consumption, refining the production process by adopting a more sustainable energy mix is imperative to lead to better outcomes. Similarly, for UHPC, in addition to using more sustainable cement types like CEM III among others (Lo Monte & Ferrara, 2020), re-evaluating the production chain could reduce transportation impacts which currently account for up to 31% of the ozone layer depletion. However, it is important to note that, due to the lack of precise data on potential Estonian producers of UHPC with alumina nano-fibres (and the related supply chain), the distances used in this study were, where possible, based on the closest suppliers to Tallinn. While these values rely on estimated distances, re-assessing the supply chain remains crucial, particularly for the most impactful components such as sand, cement, and blast furnace slag, which contribute 13%, 9%, and 8%, respectively, to the Ozone layer depletion of 1m³ of UHPC in this study, due to their high content. Table 3 : Obtained results per impact indicator. The assessed functional unit corresponds to 1 kg of alumina nano-fibres. Impact category Unit Total Acidification kg SO2 eq 2,02E-02 Eutrophication kg PO4 --- eq 1,52E-02 Global warming potential (GWP100a) kg CO2 eq 4,79E+00 Photochemical oxidation kg NMVOC 1,03E-02 Abiotic depletion, elements kg Sb eq 1,89E-05 Abiotic depletion, fossil fuels MJ 5,34E+01 Water scarcity m 3 eq 1,95E+00 Ozone layer depletion (ODP) kg CFC-11 eq 6,19E-07 Table 4 : Obtained results per impact indicator. The assessed functional unit corresponds to 1 m³ of UHPC containing alumina nano- fibres. Impact category Unit Total Acidification kg SO2 eq 3,05E+00 Eutrophication kg PO4 --- eq 1,11E+00 Global warming potential (GWP100a) kg CO2 eq 9,87E+02 Photochemical oxidation kg NMVOC 2,94E+00 Abiotic depletion, elements kg Sb eq 1,48E-01 Abiotic depletion, fossil fuels MJ 6,75E+03 Water scarcity m 3 eq 2,20E+02 zone layer depletion (ODP) kg CFC-11 eq 5,98E-05