Researchers in China have made a breakthrough by developing a new type of cement that can reflect sunlight instead of absorbing it. This new material, called supercool cement, has the potential to keep buildings cooler, cut down energy use, and help cities fight against climate change. The research team from Southeast University in Nanjing shared their findings in the journal Science Advances.
Normally, cement absorbs sunlight during the day and traps heat, making both buildings and cities hotter. But this new supercool cement works differently. It reflects sunlight away and also releases heat into the sky, meaning it does not store the heat inside. In simple words, it acts like a mirror during the day and a radiator at the same time.
Tests showed that the new cement can reduce surface temperatures by 9.7°F (5.4°C) under direct sunlight compared to traditional cement. In one rooftop test, when the air temperature was about 101°F (38.4°C), the surface of the supercool cement stayed nearly 10 degrees cooler than the air around it.
Researcher Fengyin Du, explained, “It works like a mirror and a radiator. The cement reflects sunlight away and at the same time sends heat into the sky. This means a building can stay cooler without air conditioning or electricity.”
The research team also proved that this cement is not just about cooling. It is also very strong and resistant. It can handle pressure, ultraviolet rays, corrosion from liquids, and even freezing and thawing cycles without losing its performance. This means it can be used in many places from simple houses to large highways, industrial buildings, and even in areas with extreme weather conditions.
The cement’s strength was tested against different forces such as compression, bending, and abrasion, and it showed high stability. According to the team, this makes it suitable for long-term use in buildings and infrastructure projects.
The secret behind this material lies in something called metasurface engineering. The researchers changed the chemical composition of the cement’s raw material, also known as clinker, to make it scatter sunlight instead of absorbing it. They created tiny reflective crystals on the surface of the cement that allow it to shine back the light.
The cement also has a very high solar reflectance of 96.2 percent and emits heat with an efficiency of 96 percent in the infrared spectrum. This is why it stays cool, even when temperatures rise.
To make it, the team used common minerals like limestone and gypsum, crushed them into dust, mixed with water, and poured into molds. Air bubbles helped create small spaces where reflective crystals could grow. These crystals then made the cement capable of scattering sunlight effectively.
The supercool cement is actually cheaper to make than normal Portland cement. Researchers explained that it can be produced at lower temperatures, which reduces the overall cost. They estimated that the production process is about $5 per ton cheaper than regular cement, making it practical for mass use.
Lead researcher Guo Lu said, “Applying this cooling cement to urban buildings could save a huge amount of energy and help cities reduce their carbon footprint. It is an important step in responding to climate change.”
This new cement could reduce the need for air conditioning, which is one of the biggest energy consumers in modern cities. By keeping surfaces cooler, buildings would not heat up as much, and people would rely less on electricity to keep indoor spaces comfortable.
The research team tested the cement on real rooftops. From 1 p.m. to 2 p.m., when the sun was at its strongest, the cement stayed nearly 10°F cooler than its surroundings. Conventional cement, on the other hand, heated up quickly and made the surface even hotter than the air.
Researcher Guo Lu summarized, “This innovation changes cement from a heavy, heat-storing material into an eco-friendly product that can reflect sunlight and release heat. It has the potential to transform our cities into cooler and greener spaces.”
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