Due to the urgent need for a more sustainable built environment and actions against climate change, this paper presents a literature review about photocatalytic TiO₂-based thin layers to be applied on mortars in facades. Photocatalysis may be a potential strategy against current environmental and climate challenges by transforming or eliminating hazardous greenhouse gases from the atmosphere. The main subjects researched were the coatings’ efficiency (which encompassed their self-cleaning ability, depolluting effect, and antimicrobial properties), durability, and sustainability. The method was based on the systematic literature review approach. Self-cleaning ability was the most recurrent topic retrieved from published studies, followed by depolluting effect and durability. There are few investigations about antimicrobial properties considering TiO₂-coated mortars in facades. However, sustainability studies through Life Cycle Assessment and Life Cycle Costing represented the most significant gap, even requiring broader surveys. The photocatalytic activity of the coatings is well-proven in the literature, although specific evaluations may be needed for each coating composition and testing condition to understand their performance. The type of contamination agents, TiO₂ dispersion and characteristics, dopants, nanocomposites, and substrate are among the principal agents influencing the results; therefore, caution must be taken when comparing research. Mainly, adhesion and photocatalytic efficiency after ageing were studied on durability. More field exposures may be recommended. Regarding the trade-offs concerning the environmental impacts of TiO₂-based coatings, it is urgent to clarify whether their overall outcome is indeed advantageous and to investigate their resilience regarding climate change scenarios.

This article presents the diagnosis of pathological manifestations on the mortar coating from the facades of two historical buildings of scientific and social importance in Porto Alegre, Brazil. Documental investigation, visual survey, percussion and thermography tests, mapping of damages, and characterization of the coatings were performed. Coatings were characterized by determining the binder:aggregate proportion and the aggregate particle size distribution; X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and qualitative test of soluble salts were performed. The damage maps present the extension of anomalies, like detachments and areas with moisture, which were located with support of thermography results. Mortar samples extracted from the buildings indicated binder:aggregate proportions, in dry mass, ranging from 1:1 to 1:2.7. In the binder, it was verified mainly the existence of calcite and quartz through XRD; with XRF, magnesium oxide was additionally verified and calcite was also found with TGA. Chlorides and sulfates were identified by XRF and test of soluble salts. The fineness module and the particle size distribution of siliceous aggregates from different samples were similar.

This paper analyzes the performance of various types of paints available in the Brazilian market, including PVA, matte acrylic, silicate, and lime paints within the context of their applicability to the conservation of historic building facades. Considering distinct suppliers and application methods, this study highlights the importance of tailoring paint selection to the preservation requirements of historic edifices, taking into account local preservation norms and the material characteristics of the buildings’ original construction. The paints were evaluated based on water vapor permeability, washability, and adhesion. Furthermore, the paints’ color variation with exposure to accelerated artificial aging was assessed. For testing purposes, specimens produced from cellular concrete slabs were used as substrates, which were coated with the paints under study. Based on the results, it was observed that, regarding the diffusion of water vapor, the silicate and lime paints presented the highest permeability values, and the acrylic and PVA paints had the lowest. Concerning washability, the silicate and lime paints showed the greatest wear. The adhesion tests revealed that, except for lime paint, detachment often occurred at the substrate. As for the accelerated aging test, lime paint exhibited the most significant color variation, losing its pigmentation considerably over time. With the results of this research and considering the main preservation requirements of historic coatings, silicate-based paints may be considered the most suitable.

Building envelopes coated with TiO₂-based mortars benefit from depolluting, antibiological and self-cleaning effects. Therefore, photocatalytic renders are allies in the quest for sustainability in the built environment, potentially combatting atmospheric pollution, enhancing durability and reducing maintenance needs. Surface finishing characteristics of the renders influence their photocatalytic efficiency and esthetic and functional properties. In this context, this study reviews the existing literature, focusing on proven surface-affecting parameters, the surface and color of TiO₂-based mortars, to explore their impacts on photoactive behavior. The incorporation of TiO₂ within an additional surface layer and its mixture into the mortar in bulk were observed for surface roughness. Mainly the addition of TiO₂ during casting was identified in colored mortars. Generally, a moderate surface roughness led to better photoactivity; microroughness affected self-cleaning by facilitating dirt deposition. The interaction between the surface roughness and the photocatalytic layer affected the water contact angle, regarding superhydrophilicity or superhydrophobicity. The photoactivity of colored mortars with TiO₂ depended on the color and amount of the added pigments, which influenced electron–hole recombination, physically occupied active sites or, on the other hand, led to a higher formation of reactive radicals. Surface finishing can thus be designed to enhance the photoactivity of TiO₂-based mortars, which is fundamental for current climate concerns and emphasizes the need for life cycle assessments and environmental protection.

Given the functional and aesthetic quality expected from concrete surfaces, this study investigated the influence of different formwork materials on their surface density, porosity, voids, and elementary chemical composition by relying on X-ray Microtomography (μCT), Scanning Electronic Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS). The formwork materials assessed were galvanized steel, regular plywood (pink), marine plywood, polyvinyl chloride (PVC), and silicone. μCT showed that distinct formwork affected the surface density of the concrete. In this case, specimens cast within silicone and marine plywood had similar pore volumes although different pore sizes, whereas PVC led to the highest pore volume with small pore sizes. Galvanized steel and regular plywood resulted in similar porosity. SEM showed that the concrete surfaces produced with marine plywood formwork had the highest void content. EDS identified surface products resulting from the contact of concrete with the different formwork materials, suggesting the potential migration of chemical elements. This research significantly contributes to optimizing formwork material selection and enhancing concrete quality and durability. Moreover, it establishes a foundation for further investigations into how formwork materials affect concrete surfaces and the pathological manifestations potentially arising from the molding process.