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    3D printing with clay

    A description of a new concept of underground construction is available on https://deeepunderground.com . I would like to invite you all to express you opinion, if proposed solutions can be supported by 3d printing using clay. Any suggestions are highly welcomed. A description of a new concept of underground construction is available on https://deeepunderground.com . I would like to invite you all to express you opinion, if proposed solutions can be supported by 3d printing using clay. Any suggestions are highly welcomed.

    #2
    I don't think so. While some of the ideas explored in that article are interesting, and seem as though they could work in certain circumstances, this notion of 3D printing support structures for mines out of clay doesn't appear in it. This must have been something contributed later by someone unfamiliar with the physical properties of clay. While clay scores high on any index of malleability, in its raw form (ie. not fired into bricks) it has almost no tensile strength and little compressive strength. There's a reason mines are shored up with timber or reinforced concrete and not raw clay, despite its advantages of cheapness and availability. While 3D printing offers great flexibility in shape and design, there's no way this forming technique can overcome raw clay's basic limitations as a structural material. As the warmer areas of the planet continue to get hotter, new techniques for building underground will become more critical to develop, so I don't want to discourage you from thinking about them. But think of some better way to support these excavations; 3D printed clay isn't the solution.

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      #3
      Thank you for your response. I m well informed about clay characteristics ,and i m not suggesting to use clay in raw form. It must be improved in certain way, maybe similar than cob,which is bassically a clay with straw,handled in the right way to harden after instalation. I was thinking more about of combination of putting clay in place with 3dprinters in thin layers,reinforced it with straw or som
      ​​​​ething else in other layers and dry or heat the mix to harden to recreate the cob process in modern way. Tensile strength shouldnt be big problem here. I suggested circular shapes supported by outside. But compression strenght is an issue,especially for higher construction. Anyway thank you for your response and help. If you have any new idea of this topic please let me know. Best regards. J

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        #4
        I forgot to mention, 3d printing was meant to be used for molehill structures (covered structures) not for underground support.

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          #5
          When you wrote that your proposed underground structures can be "supported by 3D printing using clay" it sounded like you were talking about printing the supports necessary for propping them up. I'm glad to be mistaken about that, because it would never work. There's no known 3D printing process for "cob", although it's probably possible to develop one. It sounds a lot like what we call "adobe", which has been used for centuries in arid countries for wall construction above-ground. and has recently been reformulated for greater durability. It makes walls that have good insulating qualities but poor load-bearing strength, something that's not likely to be improved by 3D printing. The main use of "cob" historically has been in "wattle and daub" construction, where a framework of sticks is covered with the clay/straw mixture to exclude the weather. I suppose the process of building that way could be automated to some extent, but it's hard to believe that the result would meet modern expectations of performance. Firing clay above 1500F or so will change its chemical state, prevent it from dissolving in water and increase its durability, but I'm not sure how you'd do that for a large above-ground structure. Merely heating it to temperatures under 1000F would just combust the straw without improving it at all.

          If you are really looking for innovative ways to construct large above-ground "molehills" , I'd suggest you read up on Paolo Soleri's techniques, outlined in his book "Earth Casting". Basically, he piles up a huge mound of silt with bulldozers, covers it with a layer of reinforced ferro-concrete, then uses the bulldozers to excavate the silt from the inside, leaving a free-standing structure. This doesn't require development of new technology, and is a lot quicker and more straightforward than 3D printing, as well as much cheaper.

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            #6
            Thank you again for your suggestions, but let me explain why I m so interesting in using 3d printing in this case,on example. if I would like to construct a big house with ,say, 4 apartments in one floor, each apartment has 100 m2 ,and building has 4 floors, I would need heavy mechanisation,elevators,a bunch of workers,concrete,reinforcement etc..it would take at least 6 month and would cost at least a million EUR. To do the same in the same time according my proposals, I would need 20 3d printers, build 20 circular towers simultaneously, at a rate of about 5 cm of height a day. In other words, an alternative would require 20 3d printers able to put 1m3 of clay in the right place in the right form every day for a price less (or much less) than 1 million EUR in 6 month. So The question is,if this can be done with 3d printers, and if it can be done at lower price than traditional constructions. I havent heard about that kind of construction as you mentioned, but it can be done. i designed similar construction in past so i know the logic. thank you again. I Really appritiate your suggestions. If you have some more please let me know best regards J

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              #7
              That might work if you used concrete instead of clay. People have developed 3D printing machines based on construction cranes which can print with specially-engineered concrete that have demonstrated very rapid construction times, since the form-work usually required for concrete casting isn't necessary. I'm not sure this would be much less expensive than normal construction methods, though. The incorporation of reinforcement and utilities has yet to be worked out, and the localities that would permit the occupation of a structure like this, which doesn't conform to current building codes, are rare. But that's still much more feasible than building this 4-story building in raw clay, which wouldn't have the strength to support itself, much less perform as a dwelling-place. I*'d suggest you purchase a few bags of potter's clay and experiment with it - for instance, you could build a model apartment building by hand and then put it out in the weather to see how it performs. This will teach you more about the material than any amount of drawing and dreaming.

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                #8
                Well, thank you for your suggestions, but I did my homework before I post my proposals. First, I m well aware of properties of clay. I know that must be modified before cast in. Cob (adobe) or similar techniques improve the properties of clay to a level, that 2-3 m high construction are possible. For higher construction, you need more. My proposal is based on properties of circular structure. Every circular structure, loaded from outside, can handle a significant load, which is able because of arc effect. That is because they are loaded only in compression.
                I proposed circular clay linings, modified as cob, surrounded by material from outside, which cause some pressure from outside, which again caused compression stress only in clay wall in horizontal direction, which can be handled by clay, concrete or any other construction material. More problematic is compression and shear stress on foundations, when structure gets higher, and clay, concrete or other construction materials weight push on it, so construction material must be as light as possible. This can be achieved by smart shaping of lining, by having voids, where you dont need full profile of lining to resist loads, and therefore lighter construction and less stress on foundations. For that kind of construction seems to me an elegant way to be constructed by 3d printers. But as I m not an expert, I dont really know, if this is really possible.
                I dont want to construct an underground structure by any mean, and I m not saying, that clay is the best material for doing it (by the way, the best way to construct such construction, is polystryrene or EPS block, light and strong), but if you have clay for construction material, and you want to make a construction higher than 2-3 m, its possible. But price for this is according my proposal: a) all rooms must be circular b) all constructions have to be loaded from outside and therefore underground structures.
                I really appreciated this discussion. Its a good way, to verify my ideas. I m preparing some answers for questions I received about the concept. I m asking for your permission to include a summary of our discussion into that text. Thank you and let me know.

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