On August 20, according to TASS, Chinese and American scientists have developed a new type of building material — "photonic structure cement" — that can interact with light and heat to help cool buildings. The related research results were published in the journal Science Advances.
Traditional cement and concrete tend to accumulate heat inside buildings, and cement-based building materials can only reflect 30% of sunlight and heat. This defect limits their use in tropical and hot countries. To solve this problem, a Sino-American team of materials scientists led by Professor Miao Changwen from Southeast University carried out the research and development.
The researchers found that when "photonic structure cement" hardens, its surface forms a special crystalline structure similar to the natural mineral ettringite. This structure can both reflect visible light well and almost completely transmit infrared radiation in the middle part of the spectrum. Under high daytime temperatures, it can reduce the internal temperature of buildings by 5 degrees Celsius.
The team achieved this by structurally modifying cement particles so that their surfaces naturally reflect light and conduct heat. They prepared a cement mixture that, when mixed with water, spontaneously forms clusters of ettringite crystals on the surface of the building material. To ensure even distribution in the cement, the researchers created a special silicon polymer with notches and protrusions that helps form a metasurface on the cement surface. This artificial structure consists of many repeating elements that can interact complexly with light, reflecting sunlight while not preventing heat from escaping through the building walls.
To verify the effect, scientists made miniature house models using ordinary cement and "photonic structure cement" and monitored them. The experiments showed that during the hottest period of the day, the new material reduced the wall temperature rise of the house from 60–70°C to 30–35°C, lowering the internal building temperature by 5°C. Scientists said that in the future, this material will significantly reduce the cost of cooling houses.
