Materials for Design of Photonic Metaconcrete and Radiative Cooling Application

Concrete is the single most produced material by humans. The downside of large-scale production of cement, the main ingredient in concrete, is a massive carbon footprint, responsible for about 10% of global emissions. In addition, buildings account for approximately 40% of total electricity consumption. A potential solution is to reduce the environmental impact of buildings by exploiting the radiative cooling mechanism, a passive dissipation of heat within the atmospheric transparency window (ATW), a range of infrared frequencies for which the atmosphere is transparent. The promising candidates for the effective daytime radiative coolers must possess a selective emissivity in the ATW range and a high reflectivity at frequencies outside the ATW range to minimize heat absorption from the sun. Both absorptivity and reflectivity are inherent material properties that are related to the optical and dielectric properties. We present a comprehensive study of the optical properties of cementitious oxides using density functional theory (DFT), GW, and Bethe-Salpeter equation (BSE) methods. Our particular focus is on understanding the excitonic properties of basic oxides which serve as building blocks for complex cementitious oxides such as alite and belite. We also study other clinker phases, as well as hydrated phases like portlandite and tobermorite, among others. In addition, the dielectric spectra obtained from these studies are used to investigate the light scattering properties with the goal of predicting the ideal composition, shape and distribution of the cement-based nanoparticles to increase reflectance.