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

54 2

1. Introduction The advantages gained by employing a nanotechnology-driven approach in the development of construction materials have been attracting for quite some time significant interest from both academia and industry (Sobolev & Guitierrez, 2005). Specifically, in the context of concrete, one of the most common applications of nanotechnology involves the incorporation of nano-scale constituents into the mix composition. For instance, constituents such as nano silica contribute to enhancing mechanical properties, particularly compressive strength, and improving bulk transport properties (Sobolev, 2016; Sobolev et al., 2009). Furthermore, the use of nano-sized reinforcements, including carbon nano-fibres, nano-tubes, and cellulose nano-fibres, has proven effective in enhancing various functionalities like corrosion resistance, self-curing, self-sensing ability, and durability in cracked states (Vera-Agullo et al., 2009; Zhao et al., 2020). Recent advances involve the use of graphene nanoplatelets and graphene oxide, which provide superior properties with lower loading compared to traditional nano-constituents (Alatawna et al., 2020; Li et al., 1995a; Li & Leung, 1992). Additionally, the impact of nano-constituents on material microstructure enables precise control over chemical reactions and processes that influence the evolution of material performance over time, particularly in aggressive environments (Muthu & Santhanam, 2018). Within this framework, ultra high performance concrete and cementitious composites, known for their compact microstructure and strain-hardening tensile behaviour, present a platform for the effective development and implementation of durability-driven material concepts and designs (Li et al., 1995a, 1995b; Li & Leung, 1992). Accordingly, other studies have explored the role of specific nano-constituents, such as alumina nano-fibres, in enhancing the autogenous healing capacity of Ultra High Performance Concrete mixes in chemically aggressive environments (Ferrara et al., 2019). The investigation revealed that the inclusion of alumina nano-fibres, enabled by a tailored preparation process, enhances the ability to redistribute stress in the cracked state. This is reflected in the increased number and narrower width of cracks observed during the pre-peak stable propagation phase. Moreover, the hydrophilic nature of these fibres promotes delayed binder hydration reactions, resulting in enhanced and accelerated recovery in both crack sealing and mechanical properties. This effect endures even when concrete containing these nano-fibres is exposed to highly aggressive conditions, including geothermal water with high chloride and sulphate levels (Cuenca, et al., 2021). The aim of this research is to evaluate the environmental impacts linked to both the production process of microfibers and the Ultra High Performance Concrete (UHPC) that incorporates them. The results are being analysed within the framework of an Environmental Product Declaration (EPD), highlighting the importance of offering comprehensive information on a product's environmental performance throughout its entire life cycle. This approach is essential for supporting the potential commercialization and market acceptance of the product, ensuring it meets sustainability standards. 2. Alumina nanofiber and UHPC with alumina nano-fibres: LCA system boundaries and data input As previously mentioned, the analysis in this case was carried out using the Environmental Product Declaration methodology. This approach aims to create Environmental Product Declarations (EPDs), which are comprehensive documents providing transparent and verified information about a product's environmental performance throughout its life cycle, in accordance with ISO 14025 (UNI, 2010). Typically, EPDs are developed and registered within a program, such as the International EPD® system. This method includes the following impact categories: acidification potential, eutrophication potential, global warming potential, photochemical oxidation potential, abiotic depletion potential for non-fossil resources, abiotic depletion potential for fossil resources, water scarcity, and optionally, ozone layer depletion. The functional units selected for the assessment were 1 kg of alumina nano-fibres and 1 m³ of Ultra High Performance Concrete containing alumina nano-fibres. For both, a cradle-to-gate system boundary (covering the production stage as per EN15804 (UNI, 2019)) was applied. Regarding alumina nanofiber production, the methodology aligns with the manufacturing process used by Nafen® alumina nano-fibres (Saunders et al., 2015). The concentrated alumina nano-fibre dispersions are supplied in a 10% concentration aqueous suspension and require the use of specific chemical admixtures, such as polycarboxylate sodium salt, to aid dispersion and prevent gelatinization due to the hydrophilic nature of the alumina nanofibers. The production process relies on ultrasonic and disintegrator treatment technologies. This method, frequently employed in nano-manipulation processes, produces nano-sized material slurries, dispersions, and emulsions through de-agglomeration and the mechanical effects of ultrasonic