Selective Optical Properties of Cement for Enhanced Radiative Cooling and Energy‐Efficient Construction Materials

This work evaluates the radiative cooling potential of cement as a component of photonic metaconcrete, capable of energy savings and reduction of CO 2 emissions. In particular, we present a comparative study of the optical and radiative properties of primary clinker products (alite and belite) and typical sulfate additives (CaSO 4 and gypsum) across the ultraviolet, visible, and infrared ranges. The dielectric response, emissivity, and reflectance were obtained using first‐principle calculations, specifically density functional theory, together with the GW and the Bethe–Salpeter equation methods. This advanced computational approach identified strongly anisotropic excitons within the electronic band gaps of the cement phases. Our findings revealed that both oxygen–silicon and oxygen–sulfur bonds play a central role in thermal emission within the atmospheric transparency window. The combination of selective emissivity and high solar reflectivity suggests that cement‐based nanocomposites are promising materials for radiative cooling applications. Furthermore, the reflectance measurements indicate an optical band gap of approximately 5.24 eV for alite. Overall, this work advances the understanding of the optical and thermal behavior of cementitious materials and provides insights into the design of energy‐efficient photonic concrete composites.