Development of Self-Cleaning Cementitious Panels with Nano-TiO₂ and Micro-ZnO: Aesthetic and Photocatalytic Impacts of Epoxy Resin Application

Self-cleaning materials are highly relevant for exterior surfaces, such as building facades, and for heritage conservation by preserving the original aesthetic appearance of surfaces with minimal effort and cost. The transparency of these coatings is essential to maintain the visual integrity of existing surfaces. In this context, nanotechnology has emerged as a promising alternative, introducing innovations in coatings and treatments that provide water resistance, self-cleaning properties, and protection against biological attack. Despite their potential, implementing these coatings on cementitious surfaces poses challenges related to long-term stability and performance. Unfixed particles are susceptible to displacement by environmental factors such as rain, wind, and wear, compromising durability and reducing their ability to degrade pollutants and maintain clean facades. This study developed self-cleaning cementitious panels by incorporating TiO₂ nanoparticles and ZnO microparticles at varying concentrations, applied using two deposition methods: spray and dip-coating. Rhodamine B (RhB), an organic dye, was used as a model pollutant to assess self-cleaning performance by monitoring dye degradation during irradiation cycles under simulated sunlight. A spectrophotometric analysis was conducted using the CIELAB color coordinate system to measure chromatic variation and evaluate self-cleaning efficiency. The effect of epoxy resin as a particle immobilizer was also examined, focusing on aesthetic preservation and photocatalytic performance. The results showed that neither the photocatalytic coating nor the resin significantly altered substrate aesthetics, confirming their suitability for facades and heritage preservation. Additionally, photocatalytic coatings improved the surfaces' self-cleaning properties; however, a slight reduction in photocatalytic efficiency was observed with resin application, likely due to a decrease in the photocatalyst’s active surface area. This highlights the need for further research into alternative resins or surface treatments that optimize particle fixation while maintaining high photocatalytic activity.