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A Lightweight, 3D-Printed Alternative to Reinforced Concrete Beams

Made from recycled plastic, they weigh up to 80% less

By Rain Noe - March 10, 2021

in Digital Fabrication

Reinforced concrete beams are incredibly strong--and heavy. Transporting them is difficult and requires considerable amounts of energy, and the reinforcing forms inside them use a lot of metal.

A team of researchers at the Polytechnic University of Valencia (UPV) in Spain reckon they can solve both problems with 3D printing. For three years they've been developing a 3D-printed alternative to reinforced concrete beams made from recycled plastic.

The components are snapped together, Lego-like, onsite, then concreted into place. No metal is required. "This prevents corrosion, decreases the weight and simplifies the work time required," says Xavier Mas, from the Institute for Heritage Restoration (IRP) of the Polytechnic University of Valencia. And the finished beams weigh up to 80% less than standard reinforced concrete beams.

As for how they manage to get the requisite rigidity from plastic, the researchers looked to human bones for inspiration.

"It is an alveolar structure, which makes it possible to decrease the amount of plastic used – and therefore its weight – while maintaining structural rigidity," says José Ramón Albiol, lecturer at the Higher Technical School of Construction Engineering (ETSIE) of the UPV.

This alveolar structure was inspired by human bones around the epiphysis, where there is a layer of cancellous bone with a trabecular disposition – the alveolar structure – and a thicker external layer of compact bone. "This is what we have transferred to these revolutionary beams, specifically to their profiles. It is a very intelligent natural system and its reproduction in these beams awards them, with the low structural weight, very high mechanical capabilities," adds Albiol.

3D printing makes it possible to manufacture customised pieces very near the area of implementation, which also simplifies transportation, saves costs and facilitates customisation. "To be able to customise the beams in situ makes it possible to adapt the characteristics of each of them to the structural needs at each point of construction. The possibility to recycle polymeric materials to produce the beams significantly decreases their carbon footprint," concludes Miguel Sánchez, from the Department of Systems and Computer Science (DISCA) of the UPV.

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Paul Dodd

2 years ago

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Why not extrude on site to the desired length? The joints cost material and weight. It would be nice to have more detail about strength, weight and composition. What about fire resistance?

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Jim Lewis

2 years ago

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How does snapping together affect the strength? I can see the concrete infill stiffening the reinforcing elements, and continuing compressive strength through the length, but what about the tensile strength? And what about fire/heat resistance? How do they compare in strength to a similar section of steel? The article leaves a lot of questions on the table.

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Frank Eisenga

2 years ago

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Why not just extrude the profile instead of 3D printing it? The customized parts will still need to be printed on or near the site but the longer profiles should be more affordable as extruded lengths.

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- Ray Jepson
  
  Frank Eisenga
  
  2 years ago
  
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  I think because the ends of the profile are larger to click together. Also, no one would blog about an extrusion!
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