4 ms·

Queue the next batch of YC sand companies

malloci 2y ago
SandGPT
avodonosov 2y ago
Innovation may be needed for recycling of the old concrete from demolished buildings. Including extraction of sand from it. If anyone invents a cheap process, it may have revolutionary consequences, probably.
deleted 2y ago
[deleted]
__MatrixMan__ 2y ago
I think that's a joke but honestly I think there's a disruption opportunity here. The easy thing about sand is that it takes whatever shape you want it to. The hard thing about sand is that it has to be firm (strong internal chemical bonds) and in small granules (somehow, lots of energy had to go into breaking those bonds, in the beach case this is wave energy). But if you had a large enough library of rocks with known shapes or which will break along predictable lines, and a precise enough idea of the ultimate desired shape for your project, you could skip the energy intensive middle part and just use large rocks that mostly fit instead of tiny rocks in the form of sand-based concrete. Then you'd glue those rocks together with concrete--which would still require sand, but now much less of it. I'm not sure how the monetary economics would shake out, but from an energy budget perspective it seems like a win to not require things to be broken up so tiny just to have them glued back together into something so large. "cheaper" to just mostly solve the puzzle out of already large pieces.
- bboygravity 2y ago
  Isn't this why often pebbles are simply added to the cement? How do you imagine competing in price with pebbles?
  - __MatrixMan__ 2y ago
    No I imagine competing in price with boulders and a 3d scanner.
- lazide 2y ago
  Nah, sand has huge advantages in that it has very large surface area and small physical size, while also being physically quite strong (if selected/graded appropriately). You can’t replace it with fist sized rocks and expect it to behave appropriately, regardless of ‘compensation’
- notpushkin 2y ago
  I think rectangular rocks would work best here. You can lay those down as even rows and get flat walls very easily. Perhaps we don’t need to use actual rocks, even! Dried clay can work just as well. If we put it in fire, it should become firm enough for most purposes.
- gregwebs 2y ago
  Actually there’s a lot of innovation to be had in sand itself. Currently only certain grain sizes are used. So desert sand gets skipped and beach sand gets smuggled.
- icegreentea2 2y ago
  I imagine most concrete applications in the world are actually reinforced concrete applications. Without rebar, I don't think you can build most spanning concrete structures that we're use to. This would leave block/stone to mostly go into pure vertical loading applications. It'd probably be reasonably useful for some wall applications, but that seems pretty limited. Even for a true foundation application, it seems like large stone blocks embedded in a concrete matrix would be pretty heterogenous, and you could potentially end up with weird stress concentrations that would be more difficult to model (and perhaps have less desirable failure modes) than rebar concrete. Another benefit of the "break down and put back together" approach of concrete is that it allows you to get very accurate and precise predictions of behavior. Large blocks will be less predictable. This will likely lead to requiring higher safety margins (which means more material/energy/cost).

SandGPT

Innovation may be needed for recycling of the old concrete from demolished buildings. Including extraction of sand from it. If anyone invents a cheap process, it may have revolutionary consequences, probably.

deleted 2y ago

[deleted]

__MatrixMan__ 2y ago

I think that's a joke but honestly I think there's a disruption opportunity here. The easy thing about sand is that it takes whatever shape you want it to. The hard thing about sand is that it has to be firm (strong internal chemical bonds) and in small granules (somehow, lots of energy had to go into breaking those bonds, in the beach case this is wave energy). But if you had a large enough library of rocks with known shapes or which will break along predictable lines, and a precise enough idea of the ultimate desired shape for your project, you could skip the energy intensive middle part and just use large rocks that mostly fit instead of tiny rocks in the form of sand-based concrete. Then you'd glue those rocks together with concrete--which would still require sand, but now much less of it. I'm not sure how the monetary economics would shake out, but from an energy budget perspective it seems like a win to not require things to be broken up so tiny just to have them glued back together into something so large. "cheaper" to just mostly solve the puzzle out of already large pieces.

bboygravity 2y ago
Isn't this why often pebbles are simply added to the cement? How do you imagine competing in price with pebbles?
- __MatrixMan__ 2y ago
  No I imagine competing in price with boulders and a 3d scanner.
lazide 2y ago
Nah, sand has huge advantages in that it has very large surface area and small physical size, while also being physically quite strong (if selected/graded appropriately). You can’t replace it with fist sized rocks and expect it to behave appropriately, regardless of ‘compensation’
notpushkin 2y ago
I think rectangular rocks would work best here. You can lay those down as even rows and get flat walls very easily. Perhaps we don’t need to use actual rocks, even! Dried clay can work just as well. If we put it in fire, it should become firm enough for most purposes.
gregwebs 2y ago
Actually there’s a lot of innovation to be had in sand itself. Currently only certain grain sizes are used. So desert sand gets skipped and beach sand gets smuggled.
icegreentea2 2y ago
I imagine most concrete applications in the world are actually reinforced concrete applications. Without rebar, I don't think you can build most spanning concrete structures that we're use to. This would leave block/stone to mostly go into pure vertical loading applications. It'd probably be reasonably useful for some wall applications, but that seems pretty limited. Even for a true foundation application, it seems like large stone blocks embedded in a concrete matrix would be pretty heterogenous, and you could potentially end up with weird stress concentrations that would be more difficult to model (and perhaps have less desirable failure modes) than rebar concrete. Another benefit of the "break down and put back together" approach of concrete is that it allows you to get very accurate and precise predictions of behavior. Large blocks will be less predictable. This will likely lead to requiring higher safety margins (which means more material/energy/cost).