Robotic Arms Build Roads by Binding Asphalt with Strings

The new method sees stacked layers of string and asphalt create more sustainable roads.
Chris Young
EMPA's robotic arm laying a string layerEMPA

A team of researchers in Switzerland has demonstrated how a robotic arm can lay patterns of string to bind asphalt together for a more sustainable roadbuilding process, a New Atlas report explains.

The method would remove the need for environmentally damaging bitumen, and would also make it easier to recycle road materials.

Researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) got the idea from an art and science project that created pillars using a mix of gravel and string, an EMPA press release explains.

The pillars were made by interlocking gravel with a thread that held the structures together. They reached heights of 80 cm (2.6 ft), and in pressure testing, they were shown to withstand loads equal to 20 tonnes (22 tons).

The scientists used this project as a starting point. For their research, however, they used string to reinforce layers of road asphalt. If they find a way to scale the method, it could provide a great environmental advantage over the use use of bitumen, which is extracted from crude oil.

Producing a 'recyclable pavement' with robotics

For their research, the team used the same string widely used by Swiss citizens to wrap waste paper. For their experiments, a robotic arm was deployed to stack five layers of gravel and string on top of one another in a pre-programmed pattern.

"We want to find out how a recyclable pavement could be produced in the future," explains team member Dr. Martin Arraigada. "To do this, we are using digitalized construction methods in road construction for the first time."

The team carried out load tests, revealing that the experimental road material was able to withstand pressures equal to half a tonne (0.55 ton). Computer modeling was also used to help the researchers track the movement of the stones and the tensile force on the threads.

The team did emphasize that the current form of the material would not be safe for building roads. However, they do believe their experiments demonstrate that the method has great potential for building roads via a more sustainable process.

Their work adds to the scientific community's wider efforts to find a more environmentally friendly process for road building. A research team from the University of Melbourne, for example, recently experimented with recycling face masks into road materials.

The EMPA team's next goal is to carry out dynamic load testing with rolling pressure for a more realistic simulation of road conditions.

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