When temperatures get too hot to handle, most of us crank up the air conditioning to keep cool. It does the job, but it’s expensive and uses a significant amount of energy. But now an innovation by scientists, primarily from Southeast University in China, could help us cut our reliance on AC. They’ve developed a new type of cement that allows buildings to stay cool on their own. Their research is published in the journal Science Advances.
Typically, cement absorbs infrared radiation from the sun and stores it as heat, which increases the temperature inside a building. To address this, a research team led by Wei She from Southeast University’s Department of Materials Science and Engineering modified the building material’s formula. They created a cement that reflects light and emits heat instead of absorbing it, using tiny reflective crystals of a mineral called ettringite on its surface.
The scientists developed the material from the ground up, starting with its basic chemical recipe. They ground tiny pellets made from minerals like limestone and gypsum into a fine dust and mixed it with water. The mixture was then poured into a silicon mold covered in holes that created depressions in the cement’s surface where the ettringite crystals could grow. The result was a supercool cement that acts like a mirror and a radiator, bouncing away sunlight and emitting heat.
Once the cement was created, it was put to the test on a rooftop at Purdue University. Under a strong midday sun, the cement’s surface was 5.4 degrees Celsius cooler than the surrounding air. The material also underwent rigorous mechanical, environmental, and optical durability testing.
https://www.youtube.com/embed/hHMisfFTv0s?color=whitePeeling off the recycle and reusable PDMS foil from super-cool cement surface. Credit: Science Advances (2025). DOI: 10.1126/sciadv.adv2820
Additionally, the team used machine learning to analyze its potential environmental benefits, which revealed that it could potentially lead to a net-negative carbon footprint over a 70-year period.
“We have innovatively transformed cement materials from heat absorbers to heat reflectors using a bottom-up approach,” the researchers wrote in their paper. “This breakthrough holds the potential to turn the heavy cement industry into a negative-carbon emission system, where supercool cement could play a key role in driving an energy-efficient, carbon-free future for the construction industry.”
https://www.youtube.com/embed/IVZqeRLmN2U?color=whiteA direct solidification time test. It showed the fast-setting designability of super-cool cement, which can’t be directly evaluated by traditional Vicat Needle Test. Within just 6 minutes after hydration, the super-cool cement had developed enough stiffness to withstand the impact of a 200g iron ball dropping, resulting in only a small pit. Credit: Science Advances (2025). DOI: 10.1126/sciadv.adv2820
Cool solution for a warming world
Buildings currently account for about 40% of global energy use and 36% of carbon emissions. If the supercool cement is successfully scaled up for commercial use, its benefits could be significant.
As well as helping to cool the planet, it could dramatically cut energy bills by reducing our reliance on air conditioning. And by keeping buildings and the surrounding air cooler, this novel cement could also create a more pleasant and healthier urban environment.
Written for you by our author Paul Arnold, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You’ll get an ad-free account as a thank-you.
