Scalable cooling cementitious Composites: Synergy between Reflective, Radiative, and Evaporative cooling

Promoting the sustainability of the building industry is one of the major approaches to addressing energy depletion and climate change. Here, we developed scalable cementitious cooling composites (CCCs) with superior energy-free cooling performance and environmental applicability. Optical properties, phase composition, microstructure, and silica reactivity of composites are characterized and analyzed. Onsite measurements are conducted to evaluate the surface/internal cooling capacities and validate the cooling principles and such composites’ climatic applicability. Results show that calcite, C[sbnd]S[sbnd]H phases (especially tobermorite), and a higher water-to-powder ratio can increase the solar reflectivity (R_sun). Meanwhile, C[sbnd]S[sbnd]H and calcite can also increase the spectral emissivity in the atmospheric window (ε_aw). Optimal sizes of 0.5 μm (particles) and 1.0 μm (pore size) for Mie scattering are determined by Finite-Difference Time-Domain simulations. The R_sun of 0.90 and ε_aw of 0.88 are simultaneously achieved, which are comparable to exquisitely designed polymer-based coatings, metamaterials, and multi-layer composites. The surface cooling of 17.3 ℃, internal cooling of 9.2 ℃ by solar reflection, internal cooling of 4.8 ℃ by evaporative cooling, and internal cooling above 2.8 ℃ by mid-infrared (MIR) emission are observed. CCCs are proven to provide efficient cooling in different conditions, with low investment, facile production, and high environmental resistance.