Cycling is a famously ubiquitous mode of transportation in the Netherlands—the country is home to more bicycles than people—so it seems a fitting location for the latest feat in infrastructural technology: a 3-D printed cycling bridge.
As Agence France Presse reports, Dutch researchers recently unveiled the bridge in Gemert, a southeast town in the Netherlands. The new structure isn’t much to look at; it is made of unadorned concrete, and according to Nigel Wynn of Cycling World, spans just 8 by 3.5 meters (around 26 by 11.5 feet). Built by researchers at Eindhoven University of Technology in collaboration with the construction company BAM Infra, the team claims to have created the first 3-D printed civil infrastructure.
The bridge, which connects two roads on either side of a ditch, was made with around 800 layers of pre-stressed concrete. The A key innovation of the project, according to an Eindhoven press statement, was the development of a process that allowed researchers to incorporate a steel reinforcement cable while laying a strip of concrete.
“The steel cable is the equivalent of the reinforcement mesh used in conventional concrete,” the statement explains. “It handles the tensile stress because concrete cannot deal with tensile stress adequately.”
There are several advantages to using 3-D printed concrete over traditional production methods, which involve concrete being poured into “formworks,” or molds. For one thing, 3-D printing is much faster. “No formwork structures have to be built and dismantled, and reinforcement mesh does not have to be put in place separately,” the Eindhoven statement notes. There is also more maneuverability with 3-D printing, allowing for a broader range of concrete shapes.
Perhaps most importantly, 3-D printing has a smaller carbon footprint than conventional techniques. Cement is made by heating limestone and other materials in a kiln at 1400°C. As the Columbia University blog State of the Planet explains, the burning of limestone releases CO2, as do the fossil fuels that heat the kiln.
3-D printing requires significantly less concrete than the formwork method because it deposits the material only in places where it is needed. And by extension, 3-D printing cuts down on the cement production process, which is heavy on carbon emissions. These many benefits have stoked the rapid growth in the field of construction printing, which currently boasts 3-D printed apartments, houses and even a backyard play castle.
Hundreds of cyclists are expected to zip over the Gemert bridge each day. To make sure the structure was up to the task, Eindhoven and BAM Infra tested its strength with a five-ton load. The bridge held, and with that success under their belts, Eindhoven researchers are planning to tackle an even bigger project. According to the university’s statement, the team is currently involved in an initiative to build five residential houses—made, of course, with a 3-D printer.