SpaceCrete (Formless Vertical Concrete)

This method allows concrete to be pumped into place to build walls without forms. Redimix concrete is delivered to the jobsite, then thickeners and accelerators as required are injected and intermixed in the pumping line, to give the fluid concrete the zero-slump-with-workability properties that you can see here.

This mix is suited for 3D printing. It is made with concrete ordered from a batch plant, at a very much lower cost than usual 3D print mixes, and we can keep an “open” time of several hours, if needed. We are “printing” it with a $2,500 pump.

Recipe: It is typically a 7.5 sack with up to another 300 lbs fly ash per yard added to that. Pea gravel only because that is all my grout pump can handle. The injected admix is still a secret at this point, but I can say that you can use the types of thickeners meant for tile adhesive or vertical concrete mixes (VAEs or ASEs), and the types of accelerators used for shotcrete, such as aluminum sulfate.

So this is a clever system with lots of potential. Instead of Portland cement, you could use magnesium cement or other type of geopolymer to make it greener. Expanded clay and/or expanded recycled glass or scoria would boost R-value, plus possibly add a pozzolan such as fly ash or rice hull ash. This would create a green, rot proof, lightweight, insulating building material that’s affordable, fast and efficient.

The ideal product would have even higher R-value similar to aircrete except faster setting and could be sprayed in place without need to make and mortar blocks together. Aircrete is way different than what’s shown in this video. I’m just throwing out ideas for discussion. A lot depends on the application.


25 thoughts on “SpaceCrete (Formless Vertical Concrete)”

  1. I wonder if you could create a mixture that would foam up like that foam in a can used for filling insulation cracks? Maybe injecting hot air into an aircrete nozzle so that the hot air interacting with moist cement creates steam that expands to create 4mm hollow bubbles which would boost the R value and reduce the amount of cement needed?

    • Yes, Kelly is correct,a Mayco C30-HD ball valve pump. Putzmeister and someone else have an essentially identical model, but the Mayco is the most common. $2500 was a very good deal, even needing work. Thanks.

  2. Just noticed this posting by Dr. Geiger, then also learned that he has passed on – so unfortunately never had the pleasure of meeting him and discussing his broad knowledge and insights on alternative construction. In this case he could have seen that his insightful recognition of potential merits – from viewing only one early and crude video – is validated. The methods, admix, strength and cost have all significantly improved since then, but of course Dr. Geiger had already anticipated that! Thank you very much! I am very sorry you are not still with us – to help us with your abundant knowledge that you seemed to freely share with joy.

  3. Is there any way you can share the formula and ingredients for the mix you are using in this video? It is very exciting and I want to build a remote cabin with it. Will drop box videos of finished product for you to post to your channel if you provide. Thanks!

    • It is not ready for putting in the wild yet for a few reasons, very sorry. Extensive testing – still have to make changes. This is mostly a cellulose-ether thickener, though you can get good results with an liquid attapulgite clay, such as Actigel 208 by Active Minerals.

  4. Very cool!

    I was looking into creating a concrete 3D printer that would use something like this.

    I was leaning towards an Aircrete based material.

  5. Is the admix very smelly as so many environmental friendly stuff are added? Any information about the prestressing force of the material as they are dried so fast? It is so much fun to try all this stuff.

  6. What’s up this is Aircrete Harry from YouTube. Let’s trad Admix secret. I have one you going to love testing. I’ll be making a video soon performing some test with my white powder Crystals. Email me. Bye

  7. Oh boy, you are in for an experiment! This reminds me of zero slump runway pavement mix and placement.

    You are calling it concrete. I’d call it it a slurry. I see no evidence of pea gravel as I understand the material, which I’ve only seen as small graded river chert pieces. That material you might regret using due to its hardness when cutting and drilling is needed.

    Its a 7.5 sack mix I suppose for high early setting and perhaps quick initial strength. I wonder if you are actually planning to cure this mix out to achieve its high strength potential or if the high sack mix is just achieve a zero slump quick set mix that allows for the placement technique.

    I assume after a vertical section is placed (the house) that immediate surface finishing is required. Did that have to happen so quickly that at least two people are necessary?

    Assume for a moment no rebar is placed in the wall. Would this mix still support itself without bulging or collapse? Did the reinforced wall actually bulge at the bottom?

    How long before the forms were removed?

    I would expect a lot shrinkage stresses and their results. These will show up at corners and at openings, perhaps a year from now. There looks to be a clever steel fabric detail around the openings.

    Best wishes.

    • Yes, lots of risks, unknowns and experimentation in this type of work. But it’s fun to see what people come up with. Right now I’m looking into 100% biodegradable hemp plastics.

    • Healthy skepticism is good, and a lot of people are reluctant to believe how it works – I would be one of them. Please keep in mind that this did not happen overnight – years of trials have gone into this. Here is a video showing one mix design:

      The admix is now improved over that video, and as it reacts with the mix water not cement, it can work with any binder. The more admix added, the less shrinkage, even with no curing. For example, a 40′ wall with no control joints, “cured” in the sun (exposed surface faces south) and wind, has no visible cracks. This building:

      Yes with almost 50 years in construction and engineering, I would be very skeptical too. Though in this case, no one is trying to sell you any product – only trying to interest a large construction product company into finishing this development and then marketing the stuff. No surprise that they are also skeptical.

      • Clarification: That 22′ x 40′ x 13′ high test building had (and has) no visible concrete cracking in any of the walls done with the spacecrete method. The exterior slab of the same concrete (same mix design, same batch plant), but without any 3D-admix, has minor cracks all over the place. The admix seems to prevent initial plastic shrinkage by a combo of high initial strength gain and internal curing provided by the water-absorbing media in the admix. Long term shrinkage is still possible, just like any concrete, but in many cases, there seems to be none vidible.

        Thanks Kelly, for supporting this blog and your very interesting posts made every single day!

    • Don, if the mixture is mostly air by volume, the challenge is very different. Easier because the mix is lighter, but harder because the high volume of bubbles lubricates really well. So the admix needs to be adjusted for this, and I am still working on that one.


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