'Cool' cement can cut electricity and prepare for a warmer world

A newly developed cement may be able to cool down homes without relying on intensive electricity demands for air conditioning. How does it work?

Cement usually warms up a space, but a new cooling cement has been developed. (above image for illustration only, witout reflecting the mentioned product).

Most construction materials tend to trap heat in a building. Now, a new cement does something different. It cools instead, providing more comfortable living spaces in heat-prone areas.

Heatwaves are intensifying due to climate change, putting many regions of the world at risk. This development, published in Science Advances, helps reduce electric energy demands on air conditioning. It provides an example of innovative thinking, prepared for supporting society in the future's climate.

The new cooling cement could address buildings’ notorious tendency to trap and radiate heat

Structural materials absorb sunlight, converting it to heat that warms buildings inside and out. Now, a new type of cement can avoid this phenomenon by cooling itself through optical effects. This alternative material could reduce the rising need for energy-intensive air conditioning and limit the development of urban heat domes. Cement buildings’ tendency to store and radiate heat will increase as the climate warms, accelerating energy demands for air conditioning and amplifying urban heat domes.

The value of passive daytime radiative cooling

Materials that perform passive daytime radiative cooling (PDRC) offer a solution to reduce reliance on current warmth-trapping materials used in construction. Now, Guo Lu and colleagues have developed a cement that performs PDRC through optical effects and without fillers or additives.

They created clinkers – millimeter-thick cement particles – with a custom chemical composition and strategically assembled the clinkers in a matrix that scattered light and did not absorb UV. They then used a pressure-driven approach to transform the clinker matrices into cooling cement, which contained special ettringites, or key minerals in cement, with 96.2% solar reflectance.

Real-world tests of the future-proof materials

Lu et al. tested the cement’s PDRC capability by placing it on a roof for one day. When the sun’s radiation was the highest (1:00 to 2:00PM), the cement achieved a temperature drop of 5.4 degrees Celsius (°C) compared with an ambient temperature of 38.4°C. Meanwhile, standard cement reached 59.0°C. The team also subjected the PDRC cement to freeze-thaw cycles, corrosive liquids, and additional UV radiation.

It resisted abrasion, maintained optical stability, and kept its strength. Further machine learning-based analyses revealed promising signs that the material could potentially do more than mediate air conditioning demands; It may also support supercooling envelopes (the opposite of urban heat domes) and a net-negative carbon emissions profile, as modeled in 7 cities in different climate zones, albeit with varying results.

Source:

www.science.org/doi/10.1126/sciadv.adv2820

 "Scalable Metasurface-Enhanced Super-Cool Cement" by Dongliang Zhao, Chenyue Guo, Guo Lu, Fengyin Du, Zhen Wang, Wenqiang Zuo, Xiaohang Xu, Zhangyu Wu, Chang Liu, Zhangli Hu, Wei She, Changwen Miao, Ruizhe Yang, Feilong Wu, Yanpei Tian, Tian Li.

Courtesy of Southeast University/AAAS