Science

Bacteria make waterproof mortar

Biofilm particles, which are dry-mix mortars, grow innumerable tiny spikes. That carry the water that wants to reach the surface in a way on hands: it can not penetrate and destroy the material. Instead, it rolls off easily.

Hydrogels are Oliver Lielegs field. Plastics are containing the water. They are flexible and adaptable. For example, Soft contact lenses, which cling to the eyeball.

Lamba, Professor of biomechanics at the Central Institute for medical technology and the Faculty of mechanical engineering of the Technical University of Munich, has now implemented its expertise in this area in an area, which seems to lie far away from his research: he has with the help of special hydro gels, which are produced by bacteria and called biofilms finished mortar, use as craftsmen put him on façades or Masons.

Initially, mortar is generally waterproof. He gets but fine cracks, moisture penetrates. At low temperatures it becomes ice cream, which has a larger volume than water. It blows up the mortar, the cracks are bigger and it penetrates even more water.

The building materials industry comes to the bacterium

Not so with the Lamba-mortars. He has vaccinated the bio-film materials produced by a bacterium called Bacillus subtilis. It is found in the Earth and is widely used. “We have used a simple laboratory master for our experiments, which grows well, makes much biomass and is completely harmless”, says Lamba.

microscopic roughness
When the Lotus-effect, a thin layer of air fill the microscopic roughness of the surface. Water can not penetrate this and rolls off. Photo: MPG

He mixes the bacterial product under the mortar dry. This is tied off, become so solid, its surface is hydrophobic, so water repellent. Not be whetted the surface, it forms beads which roll off like on a Lotus leaf (Lotus effect) due to its surface tension.

Slows down rising water

What causes the miraculous change of the mortar was only under the electron microscope at high magnification. The surface of the mortar is prickly like the skin of a hedgehog. Except that these spikes are just tiny. You stretch as his water contrary to prevent again because of its surface tension, the liquid from reaching the mortar The drops roll easily down.

waterproof concrete
Fresh pressed concrete shaft rings: TUM scientists want to check now whether they can make waterproof concrete by using a biofilm from bacteria.

Also in the Interior of the mortar, the researchers found such spines. There, they prevent that water rises against gravity (capillary). The spines are not a unique selling proposition for Lamba-plaster. You are also on non-impregnated material, however in lower density, that the water can reach the surface. The biofilm encourages, as researchers suspect, spine growth.

Now also concrete should be waterproof

Currently, the mortar is checked for its usability in practice. Professor Christian has great Chair for Nondestructive material testing taken over. If the mortar is actually right, I see little problems to set up him in a big way”, says Lamba. Because of the biofilm can also freeze drying. The powder leave are easy to transport and under the dry mortar mix.

Lamba now checks whether the method for concrete is suitable.

2000 years ago, ancient builders have used a special mortar, which is more stable than many modern concrete. You mixed with volcanic ash, which prevents micro-cracks.