Like anything else, concrete structures get dirty over time and it’s cumbersome to clean them up. But now scientists have developed a new kind of self-cleaning concrete that eliminates these unnecessary steps.
In general, self-cleaning materials work by combining hydrophobic (water-resistant) surfaces that cause the liquid to bead and roll down, while allowing dust and dirt to be removed along with the liquid. However, previous attempts to add hydrophobic materials to concrete have not been fully successful. For example, when used as a surface coating, they end up being scratched or worn over time. When mixed into concrete in a humid state, they reduce their strength when dry.
Under Professor Xu Xin’s leadership, researchers at the University of Science and Technology in China have come up with an alternative. They first combined wet concrete with oil, emulsifiers and hydrophobic silicone polymers called polydimethylsiloxane (PDMS). The mixture is then formed into droplets and scattered throughout the concrete substrate.
They then dried and heated the concrete, and the oil evaporated, leaving holes with small drops of PDMS coating. The resulting material has proven to be highly hydrophobic – rejecting a variety of liquids – while also being lightweight and robust.
What’s more, even if polished, it maintains its self-cleaning quality without being exposed to extreme temperatures and harsh chemicals. In addition, it has been found to have good sound absorption and insulation.
Scientists hope the concrete will be used not only in buildings and other structures, but also on anti-bacterial surfaces in environments such as hospitals. Scientists recently published a paper on the study in the Journal of Applied Materials and Interfaces of the American Chemical Society.