PSI - Issue 55

Jéssica D. Bersch et al. / Procedia Structural Integrity 55 (2024) 57–63 Bersch et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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climate for 12 months (Carmona-Quiroga et al., 2017a). Concerning ETICS protected with anti-graffiti products and submitted to accelerated ageing with hygrothermal cycles, they showed a slight darkening, a gloss increase, a partial erosion of the material, and a general reduction of the water absorption by capillarity and drying kinetics, which can affect their cleaning efficacy over time (Gil et al., 2023). In metallic substrates, weathering through UVB and condensation led to an increase in the hydrophilicity of specimens protected with anti-graffiti products based on a polyester resin, and, although color variation was considered acceptable after graffiti removal with xylene and methylethylketone, the gloss increase was excessive (Rossi et al., 2016). In concrete slabs, a permanent anti-graffiti coating composed of a fluorinated polyurethane was weathered after 500 h of ageing in a chamber with UVB radiation and after six months of exposure in the south of England, getting yellower and dark and, in some cases, losing its adhesion from the substrate, besides being partially removed by pressurized water spray; sacrificial coatings composed of a crystalline microwax were also degraded in the natural environment, becoming darker and less water-repellent due to cracking (Carmona-Quiroga et al., 2017b). Rabea et al. (2012) prepared polyurethane coatings with anti-graffiti properties with a silicone acrylic additive and, through ageing under UV irradiation, the degradation of the additive was registered; thus, the improvement of the UV resistance of the films was suggested to achieve durable protective products. In this context, Amrutkar et al. (2022) suggested the addition of silica nanoparticles to improve anti-graffiti coatings durability, especially regarding UV radiation and weathering resistance. Gao et al. (2021) produced a protective coating by cross-linking two kinds of siloxane regarding the need for durability; the anti-graffiti performance of the coating, applied to a glass surface, was considered excellent facing both water and oil-based paints and, additionally, it was not affected by harsh environments, including ultraviolet irradiation, sunlight, and corrosion. Regarding the nature of anti-graffiti products to be used, especially sacrificial systems, generally based on waxes and silicones, may have their durability affected by intense environmental conditions (Gardei et al., 2008; Gomes et al., 2017), while semi-permanent and permanent products can provide a more efficient graffiti removal (Gil et al., 2023). Cocco et al. (2015) evaluated one semi-permanent anti-graffiti product ’s durability through cleaning tests and verified that, although the technical data sheet stated the resistance of the product to three to four cleaning cycles with dichloromethane, only one cycle partially compromised the coating, leading to vulnerability of the substrate against graffiti paints. On the other hand, Lettieri and Masieri (2014) applied sacrificial water-based anti-graffiti emulsions to a highly porous stone, observing that limited areas still presented residual anti-graffiti after cleaning. Therefore, compatibility problems or harmful accumulations could arise from maintenance activities with further treatments, besides impacts on the surface characteristics (Lettieri and Masieri, 2014). García and Malaga (2012) proposed a series of durability tests to assess anti-graffiti products for use in the protection of historical porous substrates, including acid rain ageing, UV and condensation ageing, salt crystallization, and natural weathering tests; cleaning efficiency was proposed to be assessed through an absolute cleaning measure, for which classes of fulfilment were presented. In the context of climate change, climate loads such as wind-driven rain events are expected to be longer and more frequent, therefore imposing a risk of premature degradation on building elements, including walls (Lacasse et al., 2020). Hence, the acknowledged need for improvement on anti-graffiti products to protect building façades can eventually be considered enlarged. Similar to self-cleaning façades technology (Chew et al., 2017; Fernandes et al., 2020), applying anti-graffiti products to building envelopes could contribute to their maintainability. Therefore, investigating anti-graffiti products could be interesting within green maintainability performance indicators, seeking to minimize adverse environmental impacts and maximize functional, safety, energy efficiency and financial performance (Asmone et al., 2019). 3.3. Environmental and economic impacts of anti-graffiti products throughout the service life Low-invasive and eco-friendly graffiti removal techniques should be preferred instead of conventional chemical mechanical removal methods, drawing upon highly acid or basic products or high-pressure water jet; for instance, combined manual and mechanical brushing with low-pressure water steam jet, which achieved satisfactory graffiti removal mainly in ETICS with acrylic-finishing coats and EPS as thermal insulation, according to previous studies (Gil et al., 2023). On the other hand, there are, among others, paint strippers for use in substrates protected with sacrificial anti-graffiti products or even unprotected, and organic solvents recommended for slightly painted surfaces,