angle-left Four materials that seem impossible

Four materials that seem impossible

Researcher Veena Sahajwalla has invented a "green" steel from recycled tires. Credit: UNSW Sydney



If most of us were given 30 seconds to indicate some material that surrounds us on a daily basis that is experiencing a profound technological transformation, very few of us would think of the asphalt of our roads or the walls and windows of our homes. However, the development of new production techniques and the application of unusual concepts are allowing researchers and manufacturers to create innovative materials that are derived from thinking outside the box.

Bendable concrete

One of the latest innovations in the field of the cement industry is the development of a type of concrete defined as ductile, in other words, bendable. Its main characteristic is its ability to resist cracking better than traditional materials, thanks to its greater flexibility.

Victor Li, a professor at the University of Michigan (USA) who has worked on its development since the 1990s, was inspired by mother-of-pearl, a substance found on the insides of the shells of many molluscs. This organic material is both hard and flexible because its architecture "at the nanoscale" is made up of layers of a rigid mineral, aragonite, joined together by an elastic polymer that allows them to slide over one another under pressure.

The engineer says that his idea was to replicate this structure, comparable to a "brick wall", to confer ductility to concrete, so to achieve this he introduced small fibres into the mixture of elements that make it up. This new material is designed to build safer infrastructure with a longer service life, lower maintenance costs and greater efficiency in the use of resources.

This is also the case for the bendable concrete manufactured by the research group of Gabriel Arce, a researcher at the Louisiana State University (USA), which uses widely available components and can achieve a deformation capacity up to 300 times greater than traditional concrete, at a cost that is 2.5 times higher.


Unlike conventional one, ductile concrete can bend under pressure without rupturing. Credit: Victor Li.

Transparent wood

In the league of transparent materials, a new competitor to glass and plastic is gaining ground. While it may seem impossible, it is actually wood. This new variant is obtained by eliminating lignin, the chemical that gives wood its colour, as shown by two studies published by a Swedish and an American university in 2016, and by then immersing it in a particular type of resin called epoxy.

Among the main qualities of this special wood is the ability to guarantee good natural lighting. "It's very transparent, but it allows a minimum of privacy to be maintained because it's not completely translucent," explains Tian Li, one of the researchers who contributed to its creation.

Making windows with this transparent wood would, therefore, better regulate the brightness of an indoor environment because the filtering of light would not depend on how the sun moves, according to some scientists who have worked on its development. In addition, it is a material that better resists fractures and water, and is more biodegradable than plastic.


In addition to being translucent, this wood is more resistant to fractures and water. Credit: KTH. Royal Institute of Technology.

Self-repairing asphalt

The road sector is also participating in the search for new, more efficient solutions. In this area, a promising new material is self-repairing asphalt, one of whose main proponents is engineer Erik Schlangen, from the Delft University of Technology (Holland).

As he explains, asphalt is a material sensitive to the effects of water and noise, which is why a porous variety is normally used to filter water and reduce noise pollution. But this type of asphalt requires frequent maintenance because it can be damaged and broken. However, this problem can be solved, according to the engineer, by creating it from a mixture of bitumen and steel fibres. In the case of a fracture, this material will self-repair if heated with an induction machine.

During tests on a Dutch road, Schlangen and his team discovered that passing the induction-heating machine above the surface of this self-repairing asphalt every four years was enough to double its useful life. Projects like this one for the creation of self-repairing asphalt are also being carried out in Spain. For example, Sacyr participates in the Repara 2.0 project to develop new technologies that improve road pavement management and conservation.



Erik Schlangen demonstrates the new self-repairing asphalt. Credit: TED

''Green'' steel

Another field in the midst of a transformation is that of steel. Its production consumes large amounts of coke or other types of coal, which produces a heavy environmental impact; hence, for several years now, more eco-sustainable solutions have been sought. One of the most successful is that of "green" steel, invented in 2005 by Indian researcher Veena Sahajwalla.

This engineer from the University of New South Wales (Sydney, Australia) developed a manufacturing method that uses recyclable waste, such as rubber and plastics, as alternate carbon injectants, thereby reducing CO2 emissions. The technique, known as Polymer Injection Technology, has begun to be implemented by the large international steel producer Liberty.

Nowadays, the company makes steel manufactured from old car tires, a more ecological market that, she says, is expanding not only in Australia, but also in Europe and other regions of the world. Meanwhile, Sahajwalla is still looking for new ways to recycle waste to develop new materials.

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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.

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