Development of a cool concrete roof tile for buildings in Brazil

Dataset for the PhD Dissertation "Development of a cool concrete roof tile for buildings in Brazil". Author: Wellington Souza Silva. Advisor: Prof. PhD Kelen Almeida Dornelles. Co-advisor: Prof. PhD Bruno Luís Damineli. Institute of Architecture and Urbanism. University of São Paulo. 2026. Abstract: The use of high solar reflectance coatings in the building envelope is a simple and costeffective solution for reducing thermal gains by direct solar radiation. Most Brazilian research has focused on analyses and the understanding of thermal-optical properties (mainly solar reflectance) of paints, tiles, coatings, and other materials from the market. There is a gap in the design and development of new solar reflective (cool) materials, especially roof tiles. This PhD dissertation aims at the development, characterization, and assessment of a cool concrete roof tile, i.e., a high solar reflectance and high thermal emittance, for roofing buildings in Brazil. The prototypes combined 12 (non-) reflective additives (mica, limestone fillers, and pigments in white, yellow, brown, red, and black colors) across six integration strategies (sand or cement substitution, pigment addition in the mortar, single-layer coating, double-layer coating, and hybrid approaches) and two post-production treatments (no moist curing and moist curing – water bath). Through laboratory and field measurements of solar reflectance (s), thermal emittance (ε), Solar Reflectance Index (SRI), color coordinates, surface roughness, thermal conductivity, thermal diffusivity, specific heat capacity, surface temperature, and a 12-month field exposure (aging campaign), a total of 157 small-size (60x60x11mm) sample variations were tested to select one prototype composition for full-size roof tile (330x420x75mm) testing of thermal, optical, functional, physical, and the mechanical properties from the ABNT Standard NBR 13858-2. The innovative cool concrete roof tile developed has mica powder at 25% sand substitution in the mixture (1:2:0.75, i.e., cement : sand : water-to-cement ratio), TiO2 coating at 20% pigment concentration, and a transparent waterproof weathering protective layer. In small-size samples, it shows s=0.81, ε=0.86, SRI=100-101, and lightness-darkness L*=88.65, whereas in full-size roof tile, or roof assembly of 1.0m2, it shows s=0.57, ε=0.92, SRI=69-70, and L*=88.79. Mica in the mixture smoothed the surface, reduced thermal conductivity and thermal diffusivity, increased specific heat capacity, and decreased the surface temperature by ~10°C in comparison to a reference prototype. However, the cool concrete roof tile was rejected in the water absorption and flexural strength test methods. Regardless of the good results for thermal-optical properties, the innovative roof tile did not meet all requirements for a Brazilian roof tile; therefore, the research aims were partially achieved. Further investigations are required to improve the roof tile’s composition, investigate its durability, address thermo-energetic performance, and cost analysis aspects. Although focused on roofs, the results are transferable to other cementbased building materials (e.g., façade mortars and paving elements), since they share a similar mortar-based composition. Therefore, the findings of this study contribute to scalable solutions for cool roofs and support broader climate adaptation strategies aimed at mitigating Urban Heat Island effects.