A Modern Roman-Inspired Concrete with Daytime Radiative Cooling Capacity.

Addressing global warming through the modernization of buildings and urban areas is a major challenge. Passive daytime radiative cooling (PDRC) materials offer potential solutions, but none have effectively replaced concrete's dominant role in urban environments. Here, a Roman-inspired concrete with PDRC capabilities is presented, combining high solar reflectance (≈0.95) and long-wave infrared (LWIR) emittance (≈0.91). It delivers cooling powers over 45 W m- 2 under average solar intensities of 850 W m- 2 without a convection shield. On hot days (above 30°C), it stays 2°C cooler than the surrounding air under solar irradiance up to 985 W m- 2. Simulations predict this concrete can reduce energy use and CO2 emissions by ≈50% in hot regions and lower urban surface temperatures by up to 10°C during heat waves. This breakthrough offers a cheap, scalable and sustainable solution for energy efficiency and climate resilience.