Urban concrete buildings absorb sunlight during the day, heating their interiors, and emit heat at night, worsening the "heat island effect." This is also why air conditioning use surges in the summer. A material similar to air conditioning has been developed that cools concrete buildings. It is a substance that neither absorbs heat nor emits it to lower building temperatures.
A research team led by Wei She, a professor in the Department of Materials Science and Engineering at Southeast University in China, noted on the 21st in the international journal "Science Advances" that they have developed supercool cement that does not absorb sunlight but instead scatters it. Unlike conventional cement, which stores heat from sunlight, this cement reflects sunlight and does not absorb ultraviolet rays, allowing it to lower its temperature without additional additives.
The researchers first adjusted the chemical composition of the small particles (clinker) that form the basic material of the cement to create a structure that scatters sunlight effectively. They then produced cement with cooling functionality by applying pressure. The ettringite component of calcium aluminum sulfate in the cement reflected 96.2% of light while emitting 96% of the infrared heat. It achieved a cooling effect by blocking external heat while releasing internal heat.
Excellent results were also obtained in actual performance tests. The research team installed panels made from supercool cement on the roofs of actual buildings and measured the temperature. At 1 p.m. to 2 p.m. when the temperature reached 38.4 degrees Celsius, the supercool cement was 5.4 degrees lower than the surroundings. In the same conditions, conventional cement heated up to 59 degrees, showing a stark contrast.
Durability was also outstanding. Even when exposed to environments that undergo repeated freezing and thawing, corrosive liquids, or strong ultraviolet rays, the strength and reflective properties of the cement were maintained.
If this newly developed cement is commercialized, it could not only reduce air conditioning use but also decrease greenhouse gas emissions. Based on an analysis using artificial intelligence (AI), it was estimated that replacing conventional cement with supercool cement could reduce carbon emissions by about 2.9 tons per ton over 70 years.
Guo Lu, a researcher and the first author of the paper, said, "Applying this cooling cement to urban buildings could lead to significant energy savings and serve as an important turning point in climate response," adding that it is an innovation that transforms heavy, heat-storing conventional cement into an eco-friendly material with solar heat reflection and emission capabilities.
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adv2820