A circular 3D-printed concrete bridge

https://www.designboom.com/technology/holcim-3d-prints-phoen...

The components were printed off-site and then assembled on-site.

While I like the structure a lot, I think it could benefit safety-wise from a proper floor layer, as the small ridges could cause someone to stumble, specially running kids.

- The printer prints variable-thickness layers in order to have the joint faces be non-parallel

- There are no additional beams inside; it's just the concrete pieces

- They make a wooden form to support it while being assembled, and then remove it when the structure is complete

- It's unclear what the black joining material is, and whether it's adhesive

Wow, if the Romans had known about this, they could have had a much better way to build arches than all that rebar.

I guess the difficulty with 3D printed concrete is adding reinforcement, and it sounds from this like they haven't solved that, they've just used a geometry that is entirely in compression?

“Concrete is an artificial stone, and like stone, it does not want to be a straight beam, it wants to be a masonry arch.”

I wonder how much of the recycled material really is concrete: the writing seems to carefully tread around any specifics, trying to distract with absolute quantities. Could it be that this "concrete ink" is basically a composite of recycled plastic and ground concrete? I'd imagine that this could achieve limestone-like performance while pretend-solving disposal.

The segmented construction of this design is very interesting; build the pieces separately using a smaller print area, then assemble using a crane etc.

The most surprising aspect was lack of rebar.

Would love to see some time lapse. How does it stay up while you're assembling it?

It is not as impressive as it looks like.

It's a tech proof of concept. That's what it is. It says what they're testing right there in the article:

- improvements in the robustness of the digital design tools,

- closer alignment with the numerous structural design and circularity-related improvements,

- tighter integration with robotic concrete printing parameters

- extensive calibration to improve efficiency of production of almost double the number of blocks in less printing time

- after two years and in its second iteration, Phoenix adds a largely reduced carbon footprint and permanence according to building codes along with many other further improvements

So, to put it in tech terms, this is the second iteration of a prototype technology, that is now safe enough to be released as an alpha build (in the form of a small public work of art in a kids' playground). They will now iterate again and in the future try for something bigger, presumably. Not everything can be on a grand scale from the get go, more so unproved new infrastructure technology. Like, you wouldn't have used Docker ver 0.1 alpha in production, right?

Normally bridges allow you to cross over something that you could not otherwise easily cross, such as a stream, a gully, or a competing transport path.

But this bridge basically sits over some flat paths that are easy to traverse as-is, and it makes them harder to traverse, because now you need to go up and down the bridge.

Indeed, because of the bumpiness of the structure, I would not be surprised if it is inaccessible for wheelchairs and bicycles, where a flat path would have been adequate.

So as a technical feat, I guess it achieves its desired purpose, but it has negative practical value.

If you look at this from a strict engineering perspective, a set of steps resting on the hill in the background could have achieved the same result at a fraction of the cost.