Concrete, clean thyself

By Nick Carne

Chinese scientists have developed what they call a self-cleaning concrete. It is genuinely hydrophobic, they say, so liquids simply bounce off it, taking dust particles with them.

And it’s strong, heat-insulating and soundproof to boot, the research team, which was led by Xin Xu, from the University of Science and Technology of China, writes in a paper in the journal ACS Applied Materials & Interfaces.

Hydrophobic concrete and cement already are common, and research continues to try to improve them and make them cheaper.RECOMMENDED

The issue, Xu and colleagues argue, is that most use surface coatings, which can scratch or wear off, or involve adding materials to the concrete before drying, which can weaken the final product.

They say they have achieved better results “in one step through the combination of the liquid template pore formation and in situ bulk hydrophobic modification”.

In simple terms, they added an oil, an emulsifier and a hydrophobic silicon polymer called polydimethylsiloxane (PDMS) to wet concrete. With the help of the emulsifier, the oil formed many tiny droplets that contained PDMS.

They then dried and heated the concrete, evaporating the oil so that PDMS-coated pores were left behind. The resulting porous concrete is, they say, lightweight but mechanically strong.

It also repels dust particles and liquids, including milk, beer, soy sauce, coffee and dyed water, and can be immersed in the liquids and removed without leaving any stains behind.

Even with mechanical grinding, heat treatment and chemical exposure, the material remained superhydrophobic.

“With these excellent performances and characteristics and easy scalable fabrication, the concrete prepared in this work possessed a wide application prospect,” the authors write.https://cosmosmagazine.com/technology/concrete-clean-thyself