PSI - Issue 64

Reza M. Fioruz et al. / Procedia Structural Integrity 64 (2024) 1142–1151 Firouz R. M. et. al./ Structural Integrity Procedia 00 (2019) 000 – 000

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5.1. Methodology This LCA was performed based on the ISO 14040:2006 (ISO 2006) and ISO 14044:2006 (ISO 2006). The goal was to evaluate the environmental impacts of the two developed bonding adhesives, CBA and GPA, and compare them with the ones of an epoxy resin adhesive. The primary focus of this assessment was the Global Warming Potential (GWP) indicator over a 100-year time horizon. This comparison aims to identify which adhesive option presents the lowest GWP, thereby providing insights for more sustainable adhesive choices. The functional unit for this study was defined as 1 kg of bonding adhesive, which was used as the basis of comparison throughout the study. The boundary of this LCA was defined as “cradle -to- gate”, including raw material extraction and processing, transportation, and manufacturing. This LCA did not cover the construction phase, use phase, or end-of-life phase as the goal of the study was to compare the different bonding adhesives having the same end-of-life. The following assumptions and limitations were considered: i) the production site was the facilities of the Structures Laboratory (LEST) of the University of Minho, in Guimarães, Portugal; ii) there is no dataset for metakaolin (MK). Thus, existing Ecoinvent dataset related to calcined clay was adapted assuming that to produce 1 kg of MK, 1.162 kg of pure kaolin is required (Tasiopoulou et al. 2023); Epoxy resin, liquid {RER}| production | Cut-off, U dataset from Ecoinvent was used to represent the epoxy resin adhesive. For the life cycle inventory, the included materials were those specified in section 2.1. and energy inputs were captured in terms of electricity consumption required for the manufacturing processes at laboratory scale. The life cycle impact assessment was calculated using datasets of Ecoinvent 3.8 and the IPCC 2021 GWP100 method, SimaPro software version 9.4.0.2 PhD. The GWP results of the two developed bonding adhesives are shown in Table 3, where it is observed that GPA presents a slightly lower GWP total of about 2%. In contrast, both developed bonding adhesives exhibit a GWP total of less than one-fourth of that compared to epoxy resin, i.e., CBA and GPA are approximately 78% lower. From Figure 5, it can be observed that the highest environmental burden, in the three GWP categories, is associated with the energy use to produce the bonding adhesives. This can be attributed to the fact that it was considered a laboratory-scale production. As expected, the second largest contributors for GWP 100 – fossil is the OPC (~43%) and MK (~17%) for CBA and GPA, respectively. For GWP-biogenic, in the case of GPA, the second highest contribution comes from SS (~20%), followed by SH (~18%), while the CBA remains the OPC with ~13%. The results showed that although it is expected to have much less CO 2 emission with geopolymer material, there is only a slight difference compared to the cement-based matrix. This is perhaps due to the high-volume of MK in the mixture of GPA. Perhaps, substituting parts of MK with alternative aluminosilicates obtained from wastes would lead to an adhesive with less environmental impact. However, the NSM bonding performance should be considered to avoid structural performance loss. Table 3. GWP of 1 m 3 of different adhesives, kg CO 2 -eq Impact category CBA GPA Epoxy resin adhesive GWP100 - fossil 1,04E+00 1,01E+00 4,70E+00 GWP100 - biogenic 1,11E-03 1,82E-03 1,01E-02 GWP100 - land transformation 5,81E-03 6,43E-03 4,57E-03 GWP100 - Total 1,04E+00 1,02E+00 4,71E+00 5.2. LCA results