###### Abstract  
Self-cleaning cementitious materials, particularly with TiO\({}_{2}\)-based photocatalytic coatings, offer significant benefits by reducing surface deterioration and maintenance requirements, even in harsh urban environments. Despite the growing interest in self-cleaning cementitious materials, an international standard test method to calculate their efficiency has not yet been established for this specific type of substrate. The objective of this study was to evaluate and compare three different techniques for assessing the photocatalytic efficiency (PE) of cementitious materials coated with TiO\({}_{2}\): (i) spectrophotometric colorimetry (SPC); (ii) digital image processing-based colorimetry (DIP); and (iii) UV-Vis spectrophotometry (UV-Vis). Rhodamine B (RhB) was used as a model pollutant, and the photocatalytic efficiency was monitored under UV-Vis light. The results showed that each method has distinct advantages and specific challenges. SPC proved to be a practical and efficient approach, similarly to DIP, which was also accessible, providing reliable and accurate measurements. UV-Vis stood out for its precision but required careful application on cement-based substrates due to their unique porosity and adsorption characteristics. These results underscore the complementary potential of these techniques and highlight the importance of developing standardized protocols that integrate their strengths to facilitate the wider adoption of self-cleaning materials. s 2025 15 2010  
economic, social, and environmental impacts. When applied to the exterior of civil infrastructures, such as building facades, these materials are exposed to various degradation agents: dirt, organic compounds, and inorganic substances. These agents contribute to the formation of surface anomalies that can negatively affect the esthetics and durability of the materials, ultimately compromising their performance [1; 2]. The functionalization of building materials using nanotechnology has been identified as a promising solution to mitigate material degradation and even improve environmental conditions. This approach not only increases material efficiency, but also reduces maintenance costs, increases performance, and extends the life of building systems [3; 4; 5]. Thus, research has progressed to integrate active components, such as photocatalytic TiO\({}_{2}\) nanoparticles, into various building materials, including cementitious materials (in the form of paste, mortar, and concrete), asphalt, and tiles. This integration provides self-cleaning properties through the synergistic effect of photocatalysis and photo-induced superhydrophilicity, facilitating the decomposition of pollutants and enhancing the durability and functionality of these materials [6]. Photocatalysis is a process involving chemical reactions in semiconductor materials in which electrons in the valence band, when excited by light, migrate to the conduction band, leaving holes which promote redox reactions at the surface of the semiconductor. The electrons reduce molecular oxygen to form superoxide radicals, while the holes oxidize hydroxyl groups or water to form hydroxyl radicals. These reactive oxygen species degrade the adsorbed impurities, reducing their structures and mineralizing them into CO\({}_{2}\), H\({}_{2}\)O, and other non-toxic inorganic products [7] (Figure 1). Research has explored different approaches to evaluate the self-cleaning efficiency of TiO\({}_{2}\) cementitious materials. Some studies have analyzed the degradation of Methylene Blue under UV radiation and artificial rain, observing a reduction of up to 50% in the darkening of treated samples [8]. Others have investigated the effect of different TiO\({}_{2}\) concentrations in mortars, showing that higher concentrations significantly reduce soot deposition [9; 10]. There is also research that has applied photocatalytic spray films and measured the degradation of synthetic paints [11].