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Construction Corner: 3-D printing could find a home among the world’s precasters

0 49 Technology

by Korky Koroluk

The various processes that we know collectively as 3-D printing were first developed in 1981 when Hideo Kodama, a Japanese researcher, found a way to fabricate three-dimensional plastic models using polymers that hardened under ultraviolet light.
Construction Corner: 3-D printing could find a home among the world’s precasters

Three years later a team of French researchers working for the firm we now know as Alcatel enlarged on Kodama's work. But the project was abandoned when the company decided that there was no real business application for it.

Three weeks after that decision was announced, Chuck Hull, of what is now 3-D Systems Corp., filed his own patent for a stereolithography fabrication system that became the foundation upon which much of the present 3-D printing process is based.

But for several years afterwards, the process flew under the radar of many scientists. The general public heard almost nothing about it.

It wasn't until the 1990s that the technology matured enough that several authors began to speculate that 3-D printing had a place in the industrial world as people sought ways to achieve sustainable development in a rapidly developing world.

In the meantime, more and more uses were found for it, but it didn't really enter the public's consciousness until early 2014 when surgeons in Swansea, Wales used 3-D-printed parts to rebuild the face of a motorcyclist who had been seriously injured in a road accident.

Since then, it seems that 3-D printing is everywhere. That there was a place for it in the architecture/engineering/construction sector was obvious, although no one seemed sure what that place would be.

But just a few weeks ago, I was able to tell readers about a construction firm in England that is using 3-D printing to precast complex concrete panels for use in the tunnels of a new subway line under construction in London.

Now there's another example — this one in Holland.

Two or three weeks ago the Built Environment Department of the Eindhoven University of Technology began printing the parts for a reinforced, pre-stressed concrete bridge for bicycles. It's to be a part of a new section of ring road around the nearby village of Gemert. The contractor, BAM Infra, had expressed interested in using innovative techniques.

One of the advantages of printing a bridge is that much less concrete is needed than would be used by simply pouring concrete into forms. A 3-D printer deposits the concrete only where it's needed.

There's an environmental advantage there, since the production of the cement in that concrete releases a lot of carbon dioxide. Less concrete, less cement, less CO2 . Nice.

There are other advantages, freedom of form being one. The printer can be programmed to produce any desired shape with no formwork needed. And the job can be done in a shop where work can continue no matter what the weather is like outside.

On top of all that, the research team headed by Theo Salet, a professor of concrete construction at Eindhoven, has developed a process that lets them print the steel reinforcement at the same time.

When laying a strip of concrete, the concrete printer adds a steel cable so that the concrete elements of the bridge are pre-stressed. No tensile stress can occur in the concrete. A half-scale model was built and tested under heavy loads. It came through with flying colours.

So in the middle of June printing the concrete elements of the bridge began. That work is expected to be finished in a couple of months. Then, in September, the BAM company will truck the elements to Gemert and "paste" them together to form a bridge.

These two examples — the subway tunnel panels and the prestressed bridge — are said to be world firsts. They certainly won't be the last.

I have a hunch that 3-D printing technology will find a home among the world's precasters.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@journalofcommerce.com.

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