Researchers at Empa in a quest to find ways to recycle the roads after use have been successful in doing so with a robotic arm. This robotic arm functions by stacking layers of gravel and thread upon each other in a pre programmed manner. This structure which is kept inside of a test box is placed on a rubber mat in order to fix it to the ground.
This entire structure is transferred on to a rotating plate where it is kept under certain amount of pressure. The load tests conducted have found out that this road matter can sustain a pressure of 5 kN (half a tonne) without the materials leaving their place.
The robotic arm lays a pattern of string to bind asphalt together. This method will make it possible for workers to abstain from using bitumen, an environmentally damaging substance which is usually used as a binding agent while constructing roads. It would also lead to an easier and simpler process to recycle road materials.
The idea spawned from a study performance conducted by the Gramazio Kohler Research laboratory at ETH Zurich, which was designed for an art and research project. In this study performance pillars were stacked on top of each other using only gravel and strings. This proved that stability can be attained without any cement used as a binding agent, but just by interlocking gravel and strings with each other.
The string used in this experiment is the same as the one used by normal Swiss citizen for bundling waste paper together. This has elevated the cost effectiveness of this project to a whole new level.
In order to measure the pressure handling capacity of the pillars made out of gravel, tests were conducted in laboratories. These tests found out that such pillars measuring 80 cm in height and 33 cm in diameter are capable of withholding pressure up to 200 kN, which is equivalent to 20 tons. Along with these 3D models of everything were created using computers employing the Discrete Element Method (DEM). This allows the researchers to understand the displacement of each rock and the tensile forces applied on the thread. It is done so because such detailed analysis is not possible to be conducted in normal lab settings.
Another remarkable feature of the strings used in the binding process of gravel, is reduction in the amount of bitumen used. This can be proven beneficial in several ways. As bitumen is obtained from crude oil a large amount of air pollutant particles are discharged at the time of production and also while using it for building roads.
Martin Arraigada and Saeed Abbasion from Empa’s lab for Concrete and Asphalt explained, “We want to find out how a recyclable pavement could be produced in the future. To do this, we are using digitalized construction methods in road construction for the first time.”
The robotic arm has got an inseparable and unique part to play in this experiment which can’t be ignored. The string laid by this arm follow a pre programmed mandala like patterns on the gravel.
At the current moment this research done by Martin Arraigada and Saeed Abbasion cannot be implemented for road construction just yet. However, this can be a huge step towards sustainable and recyclable roads for the future.