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Putting old concrete into roads loses almost all of its value and is a pretty atrocious form of downcycling; notice that the linked article is literally about “
by szvsw 2y ago
Putting old concrete into roads loses almost all of its value and is a pretty atrocious form of downcycling; notice that the linked article is literally about “disposing” of concrete, not re-using it meaningfully. Most of concrete’s primary use case is as a structural material in buildings/infrastructure - beams, columns, slabs, etc, and we unfortunately have very little by way of re-using concrete structurally, partly due to demolition processes, documentation, rebar etc etc. While pre-cast concrete is potentially more up-cyclable, again, it’s not really designed for disassembly, re-assessment, etc, and there are very few actual use-cases/projects that have done anything of the sort, though some very cool research is being done on this at places like MIT and EPFL, including novel pre-cast concrete systems specifically designed for dis-assembly and re-use.
Part of what makes the article and methodology linked here interesting is that it a) uses waste heat which b) is already theoretically able to come from renewable sources and c) can be used to to support manufacturing of structural components further upstream in the lifecycle of cement/concrete.
- trimethylpurine 2y ago>Putting old concrete into roads loses almost all of its value Because roads can be made from something cleaner? If so, what, and why aren't we already using that something? Value wasn't really the question. Environmental care costs more. It typically means doing something that is in opposition to monetary value in order to make gain towards an environmental goal. Although, rarely, those are also in alignment to be mutually beneficial. Is this such a rare case? I'm skeptical.
- szvsw 2y agoBy value, I meant, broadly, engineering/environmental value, not financial. Its value as a material from an engineering perspective is that it (a) functions fantastically in compression and with the addition of (usually) rebar, it can function in tension and bending as well, and (b) it is generally speaking easy and cheap to build structures (of all sorts) with it. This comes from a beautiful interaction of materials - cement, sand/aggregate, steel - all working in concert together. In fact, turning concrete into gravel on roads does precisely what you suggest is a bad thing (and which I agree is bad!) - pursing an economically valuable form of recycling which is less environmentally valuable than the significantly more challenging pathways towards proper structurally valuable reuse. All sorts of things can go into aggregate for roads: various forms of sand, stone, concrete, etc. anything you can make gravel out of really. If you can instead somehow reclaim the concrete and/or the cement within the concrete for structural use rather than use as aggregate, you can displace more carbon emissions by preventing the manufacture of new cement/concrete.
- trimethylpurine 2y agoIt's interesting that the alternative things you listed that can go into roads are all incredibly expensive and also produce high amounts of carbon. I happen to live in a mining capital. Looking around, I'm convinced that there is nothing clean about sand, stone, concrete, or anything else they make gravel out of. Hence my skepticism.