A 3D concrete printer at the Eindhoven University of Technology in the Netherlands has started printing the world’s first 3-D printed reinforced, prestressed concrete bridge. The cycle bridge will be part of a new section of a ring road around Gemert in which the BAM Infra construction company is using innovative techniques.

One of the advantages of printing a bridge is that much less concrete is needed than in the conventional technique in which a mold is filled. By contrast, a printer deposits only the concrete where it is needed. This has benefits since in the production of cement a lot of CO2 is released and much less of this is needed for printed concrete. Another benefit lies in the freedom of form: the printer can make any desired shape, and no wooden molding frames are needed.

An added benefit for the researchers in the group of Theo Salet, professor of concrete construction, has succeeded in developing a process to also print the steel reinforcement at the same time. When laying a strip of concrete the concrete printer adds a steel cable so that the bridge is ‘pre-stressed’ so that no tensile stress can occur in the concrete because this is something that concrete is not able to cope with adequately.

In recent months Theo Salet’s research group made an initial scale model (1:2) and tested its safety by subjecting it to a 4,400-pound load.

It is expected that the bridge elements will be printed and ready within two months.