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

55 3

cavitation. Additionally, the dispersion process involves multiple stages, including pre-treating the fibres in water using a disintegrator machine and repeating disintegrator treatment cycles to achieve a stable semi-product. The resulting product, with its main components per 1 kg listed in Table 1, remains stable for at least 3 months post production. Due to the lack of more specific data, all the alumina nanofibere-dispersion components are assumed to be transported for an average distance of 250 km to Tallinn, Estonia, where the producer is based, by employing an EURO6 truck freight. For the production process, 45 minutes were allotted for the disintegrator and 1 hour for the ultrasonic process, with energy consumption calculated based on the technical specifications in the machinery data sheets (Desintegraator Tootmise OÜ, 2024; Inlab, 2024).

Table 1 : Alumina nanofibers dispersion: components

Aluminum oxide nanofibers (diameter 4-11 nm; length 100-900 nm)

110 g

Polycarboxylate superplasticizer

60 g

Distilled water

840 g

Regarding the composition of the UHPC containing alumina nano-fibres, the mix reported in (Cuenca, D’Ambrosio, et al., 2021), which featured an average compressive strength of 136 MPa (coefficient of variation CV= 5%) and an average σ n,max of 19 MPa (CV= 30%) has been considered for the purpose of this analysis. Specific details are provided in Table. All the UHPC constituents have been supposed transported for a distance between 80 and 200 km depending on the Estonian identified supplier. The protocol for mixing and the associated electricity consumption during production follows the procedures detailed in (Cuenca, D’ambrosio, et al.) for a total of 23 minutes and an electric power of 55 kW (Euromec, 2024). All the data utilized in this study were processed using SimaPRO software version 3.6, with the Ecoinvent data library applied during the inventory phase, which serves as a prerequisite for the output calculation phase

Table 2 : Assessed UHPC mix design

Components CEM I 52.5R

kg/m 3

600 500 200 120 982

Blast furnace Slag

Water

Steel fibers (l=20 mm; d= 0.22 mm)

Sand (0-4mm) Superplasticizer

33

Crystalline admixture

4.8 1.5

Alumina nanofibers (0.25% by weight of cement)

3. Alumina nano-fibres and UHPC with alumina nano-fibres: LCA outputs The results of the sustainability analysis are presented in Table 3 and Table 4, while Figure 1, Figure 2, Figure 3 and Figure 4 depict the impact percentages of each component for alumina nanofibers and the UHPC mix design, respectively. As demonstrated, electricity stands out as the most significant contributor across all impact categories related to alumina nanofibers, with influence indices reaching as high as 96%, particularly in the case of acidification potential. This considerable impact is largely driven by the high electricity consumption, totalling 9.91 kWh, mainly attributed to the operation of the disintegrator machinery. In contrast, the contribution of aluminium oxide is comparatively low, except in specific categories such as ozone layer depletion and water scarcity, where its impact