Most buildings nowadays are constructed using mortar materials. They are strong and relatively inexpensive. However, they are vulnerable to moisture. Now scientists from the Technical University of Munich developed an innovative way to make mortar more resistant to moisture by adding a soft, moist substance produced by bacteria.
This substance is a biofilm – a material people usually want to get rid of. Dental plaque and the slimy black coating that forms in sewage pipes are biofilms too, but this one, used in mortar, is actually beneficial. The inspiration for this research came from the conversation between two scientists – one mentioned using bacteria to create self-healing concrete and the other though of using bacteria to protect mortar from moisture. Water ingress to concrete blocks can cause some serious issues, such as forming frost can eventually crack the blocks. Mold also likes growing in moist surfaces. Water-repellent biofilms are thought to be able to prevent moisture from entering mortar.
Bacterium in question is Bacillus subtilis – it lives in the soil and is quite common and easy to culture in the laboratory. That is what scientists did and then added this moist biofilm to the mortar powder, which created something scientists called “hybrid mortar” – water was not able to wet its surface as much as it does on the usual mortar. The result is a material, which is as likely to absorb water as famous “Teflon”. The cause of such water-repelling properties are tiny crystalline spikes on the surface of the mortar, which ensure that only a tiny part of the water droplet is actually touching the surface.
Interestingly, similar spikes can be found on untreated mortar as well. However, they are too long, rare and scattered. Thus, scientists think that biofilm stimulates more uniform surface, which benefits the water-repellent property of the mortar. Now scientists are going to test the hybrid material in the actual application. Oliver Lieleg, creator of the new hybrid material, said: “If the mortar is in fact suitable, there should be no problem for companies to produce it on a large scale. We‘ve also discovered in our experiments that freeze-dried biofilm can be used equally well. Then, in a powder form, the biological material can be stored, transported and added much more easily”.
This biofilm is relatively inexpensive and produces simply. In the future scientists will check its potential to protect concrete from water as well. It may revolutionize these building materials and make buildings last much longer without any repairs.