water off a duck's back

Concrete That Sheds Water Better Than A Duck’s Back

  November 26, 2019

By Naomi Millán

Over time, with normal exposure and use, even well-maintained buildings can become a bit dingy. Dirt and grime stick stubbornly to micropores in walls and floors, or sections of building exterior are too hard to reach for any regular scrubbing. Borrowing tricks from nature for self-cleaning structures is one way to deter this slow decline. 

Hydrophobic materials are those which shed water very easily. Already on the market for some time, hydrophobic coatings can be applied to surfaces in order to improve their ability to shed rain from exterior walls, all the while sweeping away dust and other particles which could otherwise lead to mold or algae growth. Other applications include prolonging the life of wooden structures, or avoiding stains on floors. 

However, coatings can wear away or scuff, requiring reapplication.  As an alternative, scientists have discovered a way to make hydrophobic concrete, with the desirable property throughout the concrete, not just at the surface layer, according to the American Chemical Society (ACS). And instead of adding a hydrophobic material to the concrete, which tends to weaken it, the researchers altered the structure of the concrete to achieve the hydrophobic effect. 

The hydrophobic concrete was created by mixing an oil, an emulsifier, and a hydrophobic polymer into the wet cement, and then cooking out the oil so that a matrix of polymer-coated pores remained. The resulting material is mechanically strong, lightweight, absorbs sound, insulates against heat loss, and resists liquids, according to ACS. In a video demonstrating the material’s hydrophobicity, liquids such as water and soy sauce dripped onto it instantly bead and bounce off. According to ACS, the hydrophobic property of the concrete is not affected by mechanical grinding, or heat or chemical exposure.   

Naomi Millán is senior editor of Building Operating Management.



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