Fantastic concrete

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Concrete is definitely not the most glamorous materials. However, it has been rethinked by researchers to finally shine under the spotlight!

Science Shapes Light to Create a Work of Art

Four aluminum plates tilted skyward transform the vault of the Rolex Learning Center into a giant screen. EPFL (École Polytechnique Fédérale de Lausanne) researchers used the so-called “caustic” effect of reflection to create bright shapes that morph and move with time and season.

© 2015 EPFL/Alain Herzog

© 2015 EPFL/Alain Herzog

When walking into the Rolex Learning Center, one immediately encounters these four large metal plates that are completely smooth and barely curved. On cloudy days it is impossible to imagine what purpose they serve. “The many fingerprints on them testify to the curiosity they generate,” says Mark Pauly, project head. However with a single ray of sunlight, the hidden function of these plates is illuminated. Looking up, one discovers four portraits of great leaders in science and architecture.

Thanks to the caustic effect, Marie Curie, Alan Turing, Eileen Gray and Rachel Carson appear under the vault of the RLC as soon as the light hits the metal plates. This effect can be observed everywhere around us. Glass, water and shiny metal objects often create seemingly random patterns on nearby surfaces through the reflection and refraction of light. When these models are used in computer graphics, they are referred to as caustics. Using algorithms developed by the Computer Graphics and Geometry Laboratory (LGG), researchers were able to control and organize this caustic effect into coherent pictures.

After experimenting with this new technology by initially passing light through transparent acrylic plates, it took Mark Pauly’s team over a year and a half of work to achieve this amazing installation on aluminum plates. This time, however, light is reflected by the material.

Through the successful installation of sol.id, the researchers were able to show that the algorithms they developed can be used in various fields such as architecture, design or technology. Mark Pauly clarifies: “We are exploring these different avenues via our startup, Rayform.”

When in Switzerland, researchers explore the caustic effect, in Denmark, they bet on LEDs!

Illuminating concrete

A new technology combining the robust properties of concrete with LED and the diversifying applications of optical fibres means that in future, it will be possible to display art, advertisements, and films directly on rough concrete surfaces.

Together with a number of international partners, and in collaboration with the Danish Technological Institute and the Danish company Dupont Lightstone, DTU has received EU funding for developing and maturing the new screen technology. The target market has been part of the project from the very outset in the form of a manufacturer of advertising signs, who is buying the product when it is ready for launch.

Although the idea behind the new product sounds fairly simple, it presents a number of technological challenges. The principle is an LED screen hidden behind several centimetres of concrete. Optical fibres are embedded into the concrete and transmit the light from the LEDs to the concrete surface, making it possible to display moving images directly on the surface.

Optical fibres cast directly into concrete offer unprecedented opportunities for displaying films, advertisements, or football matches directly on the wall. In high quality and without mounting any screens.

Optical fibres cast directly into concrete offer unprecedented opportunities for displaying films, advertisements, or football matches directly on the wall. In high quality and without mounting any screens. Photo: Mikal Schlosser

“The most obvious advantage of this type of screens is probably the robustness of the design, which is ideal for, for instance, bus stops where advertising signs are often vandalized. In addition, the technology provides for a number of architectural possibilities, such as using light to create a certain atmosphere in a room, thereby extending its range of applications. In the long term, the screen may also be used for more practical purposes, for instance to transport daylight into hospitals to enhance the quality of life for the sick.”, explains bo Jacobsen, Managing Director at Dupont Lightstone.

If the concrete is not robust enough, european researchers probably have a solution…

Self-healing concrete to improve the durability of structures

Manual repairs to structures lead to endless traffic jams everywhere, but imagine that all this misery on the road could be eliminated by means of concrete that repairs itself. That is exactly what the European project HEALCON aims to achieve, the development of self-healing concrete to improve the durability of structures.

Ultrasound measurements on concrete with self-healing capabilities. (Picture: Werner Bachmeier / TUM)

Ultrasound measurements on concrete with self-healing capabilities. Photo: Werner Bachmeier / TUM

Structures made of self-healing concrete have an inherent healing mechanism that becomes active when a crack appears, thus rendering manual crack repair completely obsolete. In order to obtain such automatic crack closure, HEALCON European project partners are investigating the use of polyurethane-based polymer resins, superabsorbent polymers and bacteria. At Technische Universität München, the efficiency of those three self-healing mechanisms is investigated. With the help of non-destructive testing methods, Professor Christian Große’s group is assessing how cracks occur, how the healing agents are released and, finally, how efficiently they did their job in healing the cracks.

The first stage of this project has already yielded very promising results on laboratory scale. In proof-of-concept tests, glass tubes with encapsulated pu-based resins were used. Also the healing mechanisms of micro-encapsulated CaCO3 precipitating bacteria as well as of superabsorbent polymers were examined. All three healing agents have shown great potential. However, to up-scale the technique and make it compatible with conventional concrete production and placing methods, further research is necessary.

Building with concrete that is able to heal itself? It might seem like a far cry, but if microbiologist and inventor Henk Jonkers from the TU Delft has anything to do with it, this will soon be reality. This Dutch researcher has developed the bio-concrete of the future, inspired by nature: concrete with bacteria embedded in it. Henk Jonkers and his bio-concrete of the future have now been nominated for a European Inventor Award, an initiative of the European Patent Office (EPO).

Before self-healing concrete can be brought onto the market, stakeholders require a proof of efficiency of the healing process. Therefore, non-destructive methods (such as acoustic emission analysis and the time-of-flight ultrasound technique) have been tested on a laboratory scale. They allow us to detect visible and invisible defects in structural elements and make it possible to assess characteristic parameters like strength and Young’s modulus. Later on in the project, these techniques will be applied to construction elements (e.g. large beams) and finally also to constructions in-situ, like bridges or slabs.

All these examples will probably be part of our daily environment in a more or less near future. If you’re interested in stunning futurist architecture, you might enjoy a visit at the Expo Milano, where the Italian pavillion (among others) also rethinked concrete. The Palazzo Italia, designed by Nemesi & Partners is wrapped by basketlike concrete panels with patented technology: when activated by light, they are designed to capture pollution in the air and transform it into salt, thereby reducing smog. Thrilling!

Sources: Articles by Sandy Evangelista for Epfl Mediacom; Katrine Krogh-Jeppesen for DynamoUndine Ziller for TUM.

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