Printed House (Concrete) failed in-situ strength tests 2

[JAE]

A printed house in Iowa was being built in Iowa and the test cylinders apparently came in at >5,000 psi compressive strength.

However, upon testing the concrete in place it wasn't that strong so they decided to tear it down and start over....an engineering failure of sorts.

https://hackaday.com/2023/11/29/iowa-demolishes-its-first-3d-printed-house/

I don't know anything more about this house other than what's in the link but my first thought was that this "printing" of concrete relied on repeated placement of concrete in the open air.

Did they not cure the concrete properly (i.e. test cylinders don't match in place strength)??
Normally concrete wass are formed and the forms act as a form of curing. This is simply stacked passes of concrete exposed to much more evaporation.
I could only guess that the curing may have been immediate spray curing applications as the wall was sequentially placed. Seems awkward.

That's what appears to be the case to me.

 

[hokie66]

When high tech weds low tech, the marriages are not always successful. That's life.

 

[Sym P. le]

Obviously a printing error. It sounds like they were able to meet the design specs with updated drivers.

 

[phamENG]

Clearly they didn't understand the meaning of "PC LOAD LETTER"

 

[dik]

5 ksi concrete seems awfully high for a house.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[HTURKAK]

My opinion is , if there is no formwork , literally means , no compaction of concrete , no vibration, less curing and rapid drying.

Moral of the story ; It is not reasonable to print everything..

Just saying..



Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[waross]

Typographical error?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[moon161]

That's interesting. They might have to change some things, but I wouldn't stop trying. Maybe they didn't strength test at proof of concept or proof of process capability when they should have. King Arthur didn't stop when John Cleese said 'Your mother was a hamster and your father smelled of elderberries!' did he?

 

[Just Some Nerd]

Why don't they just 3D print some custom formwork for the concrete instead

----------------------------------------------------------------------

Why yes, I do in fact have no idea what I'm talking about

 

[EdStainless]

Just as trying to additively build metal parts doesn't really work (poor toughness, highly directional properties, low corrosion resistance) with standard alloys why would you expect this to work with standard mixes.
It may take a little adjustment or it may take a lot.
They will get there eventually.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

A following form section and a small vibrator? Corners will be challenging but do-able.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Sparweb]

This may be a case of an experiment that just needs more iterations before it can be done right.
Publicity distorts the (perception of) progress, too. Give them a chance...

 

[JStephen]

I would think just a little bit of cold-joint effect would mess it up.
Although, seems to me to be a bit of a solution in search of a problem, based on that clip.
I remember reading long ago that one of the problems with alternative house construction, regardless of what it was, was that there wasn't that much of the cost of a house actually in the structural aspect, there was a lot of it in the foundation, the plumbing, the wiring, HVAC, insulation, etc. and whether you used haybales or old car tops for the house, you still had all those aspects.
I am reminded also of Thomas Edison's concrete houses as a solution to the problem.

 

[Alistair_Heaton]

From my experience with the barn the foundations was 6k

Roof 3k insulation for roof 1.5k


Concrete ceiling panels 6k

Blocks 3.5k mortar 500.


The biggest expense is labour and ticking boxes if your using a construction company.

Material wise I am under 20k.

If I was to do it getting a construction company in it would be 80k. For a 15m x 6m 1.5 floor heated workshop. Residential house would be 120k. Which would be maybe 10% extra materials.

The biggest problem is finding labour here to build.

I presume printing requires much less labour on site.

 

[Tomfh]

There’s a new one in Dubbo (regional Australia) that has some cracking issues. It’s used as an amenities block.

During construction:

https://www.abc.net.au/news/2023-07-13/construction-3d-printing-technology-dubbo/102587594

Recent reports of cracking.

https://amp.9news.com.au/article/5c14b63c-1c66-425b-88e4-1fe39e9e4fed

Decent shrinkage cracks by the look of it.

Dubbo is also generally deep highly reactive clay, and any brittle non articulated structure with long walls (masonry, plain concrete) is going to crack. So that could be playing into it too.


This “technology” seems a bit gimmicky to me. It’d be quicker to assemble some flat pack frames than “print” a building.

 

[Tomfh]

Jstephen, yeah you can see the delamination in the demolished parts. It has to play a role. Also in the cracking photo I posted above, you can see the vertical crack terminating at a layer boundary, suggesting a potential delamination.

 

[hokie66]

I think this thread is definitely in the right forum.

 

[phamENG]

These don't save that much labor - yet. For a house, a typical framing crew around here is only 5 or 6 people. A foundation crew 3 or 4. The 3D printer needs 3 or 4 people to run it, and they're likely higher paid since they have to handle both the miscellaneous labor aspects AND are essentially skilled machinery operators. So long as they can scale that - doing larger/more complex builds with the same crew or the same crew doing more smaller and simpler builds than a typical housing crew - they can create savings on the labor side. But as of right now most of them haven't attained that scale.

As for material...you can certainly get a stronger house with this method. That will be valuable in a lot of areas - the southeastern US comes to mind as these could compete well with CMU houses in hurricane prone regions and the lack of termite food is nice in that area as well. But for the other 80% of the US, a panelized, light frame wood house could go up faster and cheaper than this with more reliable and predictable results. If somebody wants to disrupt the space and lower housing costs as impacted by the cost of the structure itself, expanding the reach of prefab housing (panelization, manufactured, etc.) would probably be a better way to go.

EDIT: I say you can get a stronger house...but it has to be properly detailed, and the materials have to be right. I wonder if anyone has tried using any type of fiber reinforcement to control cracking? I'm dubious of synthetics, and steel would probably not play nice with the printer, so I don't know. Introduction of horizontal reinforcing may be required, which adds some labor back in...

 

[hokie66]

I think by those photos that horizontal reinforcement is not present. Thus the cracking.

 

[spsalso]

So the process couldn't build a 4-hole outhouse in Australia. Kind of impressive.

Or perhaps the process does work, but the design engineer didn't.


spsalso