Enhancing Optical Performance of Cementitious Composites with Nano-TiO₂ based surface treatment: A Cost-Effective Approach to Boost Solar Reflectance Index

The Solar Reflectance Index (SRI) is a critical parameter for evaluating a material's ability to reflect solar radiation and release absorbed heat, affecting its surface temperature and thermal performance. Nano-titanium dioxide (NTiO₂) is widely used to enhance SRI in paints due to its high refractive index and light color; however, its high-cost limits large-scale intermixing applications for cementitious composites. This study investigates a cost-effective alternative by applying a NTiO₂-based cationic molecular emulsion as a surface treatment. Cement paste samples (5 × 5 × 1 cm for solar reflectance and 10 × 10 × 2 cm for emittance tests) were cast using Type-1L Portland-Limestone cement and a 0.5 water-to-cement ratio, then cured for 14 days under controlled conditions. Samples were evaluated using a UV-VIS-NIR spectrophotometer and a pyranometer for solar reflectance (SR) and an emissometer for thermal emissivity, with SRI calculated under standard conditions. Results indicate that treated samples exhibited consistent increase in SRI compared to untreated samples, demonstrating the potential of surface treatment as a cost-efficient method for improving reflectance properties in cementitious materials for combating urban heat island effect.