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.



SpaceCrete (Formless Vertical Concrete) — 5 Comments

  1. 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.

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