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--- writing:building_materials [2025/12/02 22:06] – JacobCoffinWrites
+++ writing:building_materials [2025/12/03 01:56] (current) – JacobCoffinWrites
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 Even concrete slabs can be [[https://www.finecutusa.com/concrete-slab-sawing-for-demolition-how-it-works/|cut up]] [[https://www.sciencedirect.com/science/article/pii/S095965262401014X|to produce new building materials]] or [[https://www.sciencedirect.com/science/article/pii/S0959652622048090|reused in creative ways]]! This is huge as concrete rubble accounts for [[https://concretecaptain.com/what-happens-to-concrete-after-demolition/|25]]-[[https://www.sciencedirect.com/science/article/pii/S095965262401014X|30%]] of solid waste in landfills.
-Concrete rubble can also be reused in other ways, [[https://slrpnk.net/post/11909269|such as in landscaping]]. There's also a rich history of cobblestone buildings where concrete rubble may be a suitable replacement for stone.
+Concrete rubble can also be reused in other ways, [[https://slrpnk.net/post/11909269|such as in landscaping]]. There's also a rich history of cobblestone buildings where concrete rubble may be a suitable [[https://www.mdpi.com/2075-5309/15/9/1437|replacement for stone]].
 === Geopolymers ===
-If you're looking for a drop-in replacement for CO2-producing Portland Cement then you probably want Geopolymers.
+If you're looking for a drop-in replacement for Portland Cement (which is used to produce the vast majority of our built-up concrete environment) then you probably want [[https://www.youtube.com/watch?v=_b5dgyB6K6w|Geopolymers]]. The concrete industry is a huge portion of human CO2 production today (around 8% total), due both to the release of CO2 from the chemical process of baking the limestone, and from burning fuel to produce the tremendous amounts of heat necessary for that reaction.
+Geopolymer is a fairly new material/process which uses a different chemical reaction to turn a mix of powders and water into a solid block of stone. It's seen some real life use and a lot of testing, and appears to cover all the uses of concrete, and to [[https://www.sciencedirect.com/science/article/pii/S221450952500467X|actually surpass it in some areas]]. Further, it's almost carbon-neutral, and repurposes industrial waste as a primary ingredient.
+One thing to track is that geopolymers require a source of calcium aluminate. This can be Metakaolin (which would require mining) but there are a variety of industrial wastes which can provide this ingredient just sitting around poisoning huge swaths of land. Removing these waste heaps and safely containing them is absolutely something that should be done (for both the surrounding habitats and any neighboring people) but is often such a huge and expensive undertaking that it isn't done at all. Turning these waste products into a useful //input// for construction materials would enable Superfund-style cleanup and disposal with the safe disposal half of the work already guaranteed. It's a win-win.
+Using them to produce geopolymers would be a win-win which produces our built environment while also providing containment for
+  * Blast Furnace Slag
+  * [[https://www.researchgate.net/publication/272616236_New_Geopolymers_Based_on_Electric_Arc_Furnace_Slag|Electric Arc Furnace Slag]]
+  * Fly Ash
+  * Palm Oil Fuel Ash - left over from the burning of palm shells and husks and fibers in the production of palm oil (the industry has issues, but it seems like it could be done sustainably).
+  * Quartz mining tailings
+  * Sewage sludge
+  * [[https://www.youtube.com/watch?v=1rcCSDVIUtg|Mineral wool waste]] -this compliments urban farming as mineral wool is a waste product of hydroponics, as well as used for housing insulation.
+The base materials are very common on Earth and the number of possible sources are remarkable, with more or less levels of energy in processing.
+**The Differences:**
+Even if you haven't poured concrete yourself, you've probably noticed that for big construction projects, concrete is usually mixed at a factory a couple hours drive from the work site and delivered by caravans of [[https://en.wikipedia.org/wiki/Concrete_mixer#Cement_truck|cement trucks]]. This would change with Geopolymer. Compared to concrete geopolymer hardens very rapidly and so would often be mixed for use on-demand at the work location even at a relatively large volume. So you would have a pre-mix of the dry ingredients then an on-demand liquid mix of water, alkaline 'activator' (sodium silicate waterglass --usually pre-diluted with water as it's physically heavy and can be very viscous, but also shipped as a powder), and 'hardener' (sodium hydroxide). The fluids might be premixed together or added individually, the water content adjusted according the latent moisture in the aggregates and the work site (like traditional concrete geopolymer can be poured and cast underwater).
+From a visual standpoint, there's probably not much to see with geopolymer production because of the simplicity. It's basically just a measured mixing process. And that work could be done in most any conventional industrial building or workshop. The huge roaring, [[https://en.wikipedia.org/wiki/Cement_kiln|rotary kilns]] used for Portland cement would be unnecessary, though some application of heat may be necessary depending on the source ingredients being prepared. This prep would probably be done near whatever heap of industrial waste is being used, because it's more efficient to transport refined materials than crude materials.
+**Why haven't we switched over already?**
+Some jobs have! The biggest real-world use I've found so far was [[https://www.unsw.edu.au/news/2015/05/a-major-milestone-in-the-use-of-geopolymer-concrete---brisbane-w|an airport]] [[https://https://earthfriendlyconcrete.com/building-construction/toowoomba-wellcamp-airport/|in Australia]] but the companies specializing in it have plenty of [[https://www.wagner.com.au/main/our-projects/|other projects]] to brag about.
+The big difference is financial cost and inertia. Portland cement has been around for a long, long time, and the industry has had a lot of time to make improvements to their processes to drive down cost. It's also a known factor - civil engineers tend to appreciate consistency and Portland cement is a very well-understood material. They have entire books on its performance and limits in various conditions, and procedures for mixing, transporting, and pouring it in just about every circumstance you can imagine.
+That institutional familiarity isn't there yet with geopolymers, so choosing to use it in a project probably feels like a risk.
+That said, a solarpunk society is likely one that actually tracks its externalities and tries not to produce waste it can't account for, and once you factor in the true costs of Portland cement, the mining, the transportation, the CO2 production, geopolymers are a rather straightforward replacement.
+=== Cob ===
+Cob is also popular with the self-sufficiency types who build thermal mass heaters and [[https://insteading.com/blog/rocket-mass-heaters/|rocket]] [[https://commonsensehome.com/rocket-mass-heaters/|mass]] [[https://permies.com/t/265979/dry-cob-rock-solid-frame|heaters]].
-Geopolymer is almost carbon-neutral, repurposes industrial waste, covers all the uses of concrete, and is much better performing overall. The only reason it hasn't replaced Portland cement already is the broad hegemony of the established industry --which won't matter as industry localizes. Ideally, we want a carbon-negative alternative to allow our built habitat to become a carbon sink, but that's going to take a while. In the meantime, geopolymers are probably the best we can do. So where concrete construction can't be replaced, that seems more likely to become the cement alternative of choice.