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Concrete: The material that's 'too vast to imagine'
- danpalmer 5y agoConcrete is one of the biggest sources of emissions in the world and it feels like a blind spot in our push for greener solutions. Is there any research being done into alternatives that will scale to what we use concrete for? I've seen alternative home building methods, and different urban planning can reduce the need for large buildings that need it, but I haven't seen good alternatives for roads, tunnels, bridges, etc. Steel sometimes works but has its own problems and is more expensive.
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- wil421 5y agoWhy don’t we focus on the problems we can solve today? Cars, power generation, and improve industrial process that emit green house gasses. We could solve these issues “today” in a sense. Creating new carbon neutral building materials that last as long as current stuff seems like a huge risk. https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...
- ajmurmann 5y agoWhy not both? If we had a carbon tax the market would drive us to save wherever is most achievable
- yonaguska 5y agoThat is until the well-connected lobby carbon tax loopholes into the implementation and use the carbon tax yet another tool for regulatory capture to stomp out competition. Or, companies simply shift more production to developing countries to skirt taxes. We can create ecological disasters over there instead... While I like the idea of attaching monetary costs to otherwise ignored externalities, I don't see the carbon tax having any chance of being fairly and effectively implemented.
- kaibee 5y ago> That is until the well-connected lobby carbon tax loopholes into the implementation This is a fully general counter-argument against doing anything. iirc Canada has a carbon-tax and its working fine?
- orhmeh09 5y agoWorking fine by what measure?
- imtringued 5y agoIntroduce CO2 tariffs. Get the republicans on board through protectionist policies that actually make sense.
- csw-001 5y agoIt's funny you should say this - I just recently was on an airplane with a bunch of folks returning from a big Vegas concrete convention. Eavesdropping a bit here and there, it seemed the topic of "greener" concrete was big. The person in the seat next to me was describing how they recently started using a concrete and steel fiber mix so they could pour less and achieve the same strength and durability - the main "customer pitch" she told me was that it would was a lot greener. No idea if any of that is true, but it was interesting to see how focused on it they all were.
- ceejayoz 5y agoI'd imagine it's kinda like "clean coal" - more marketing buzzword than actual significant benefit.
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- TheFreim 5y ago> significant benefit Isn't at least a little benefit alright? It's not "significant benefit" or "nothing.
- ceejayoz 5y agoNot necessarily. At times, a tiny band-aid on things can be counterproductive. See replacing plastic straws with paper/reusable ones; it's a drop in the bucket, and it's used in part to distract from the much larger overall issue of single-use plastics. https://en.wikipedia.org/wiki/Greenwashing https://en.wikipedia.org/wiki/Greenwashing
- TheFreim 5y agoI don't see how paper straws distract from anything. Every time I see a paper straw my immediate thoughts are about how it's not plastic that'll be getting thrown out.
- 0x_rs 5y agoConcrete production represents 4-8% of all worldwide CO2 production. It's a significant percentage. There's talk on sequestering CO2 in concrete itself but I'm not sure how far it has gotten. I do remember some plants in France or Germany having facilities to process clinker byproducts. I wonder how more efficient is that.
- kieranmaine 5y agoThis company creates reduced carbon cement - https://www.ecocem.ie/ecocem-materials-limited-raises-e22-5m-from-breakthrough-energy-ventures-and-breakthrough-energy-ventures-europe/ https://www.ecocem.ie/ecocem-materials-limited-raises-e22-5m... This podcast has a couple of interesting mentions on low carbon concrete - https://www.npr.org/transcripts/923966126 https://www.npr.org/transcripts/923966126
- nelblu 5y agohttps://www.carboncure.com/ https://www.carboncure.com/
- LeifCarrotson 5y agoHonestly, I think we actually want a high-carbon cement: One full of graphene or other carbon compounds, pulled from the atmosphere. Per the article yesterday [1] we need to remove 2 teratonnes of CO2 from the atmosphere to meet IPCC targets. Maybe some of that will be done by taxpayer-funded carbon sequestration operations that exist only to pump the carbon 'away' in underground reserviors. But I think that if we've laid down 1 Tt of concrete, and could develop something better than that which is carbon-negative, people would be more than happy to pay for that CO2 sequestration, and that progress might actually survive an election cycle. [1] https://spectrum.ieee.org/energy/renewables/engineers-you-can-disrupt-climate-change https://spectrum.ieee.org/energy/renewables/engineers-you-ca...
- vegetablepotpie 5y agoYes there is. Geopolymer cement provides an 80% reduction in co2 emissions vs traditional cement. CarbonCure has developed a version of concrete that absorbs co2 during its production, though it cannot be poured and can only be used to make prefab shapes [1]. An issue with these new cements is that there is no economic incentive for companies to change production processes and switch. [1] https://youtube.com/watch?v=MkE-2npiqFc https://youtube.com/watch?v=MkE-2npiqFc
- tastyfreeze 5y agoIt isnt just cost that prevents a switch. Some building codes explicitly state Portland cement as the allowed material. Geopolymer proponents have been working to change building code to stating required material properties instead. Unsurprisingly, geopolymers have taken off in countries with less regulation.
- legym 5y agoBeen looking into graphene and it can reduce the amount of concrete and increase the strength. Of course, can graphene be made at a commercial level and out of the lab https://www.graphene-info.com/graphene-based-concrete-used-commercial-setting-first-time https://www.graphene-info.com/graphene-based-concrete-used-c...
- XorNot 5y agoConcrete though is big and stationary. It needs heat, not combustion to make, so it is amenable to fuel source switching. For me it's in the bucket of "problems which don't matter till we solve electricity". Clean, cheap electricity == clean, cheap concrete.
- phreeza 5y agoThe majority of the CO2 emissions from concrete come from the production chemical reaction, not from the heat generation, though.
- XorNot 5y agoWikipedia [1] suggests 50% is from calcination and 40% from burning fuel. There's plenty of room for reductions on the fuel side. [1]https://en.wikipedia.org/wiki/Environmental_impact_of_concrete https://en.wikipedia.org/wiki/Environmental_impact_of_concre...
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- patrickk 5y agoOne material that should be used much more in building but isn't: straw! It's become a recent obsession of mine. * has a long history of use (no research needed) * is eco friendly (in fact sequesters carbon) * cheap * readily available * pliable material that is forgiving to build with, even for novices * quick to erect walls * is a waste material - usually ploughed back into fields or burned * has very impressive thermal and sound insulation, so no additional insulation is needed, unlike a concrete walled home or building I could go on.... Of course not every building or structure can be made from straw bales, but many houses, warehouses or smaller commercial buildings could be. It's a very low hanging fruit in the battle against climate change. https://www.amazon.com/Building-Straw-Bales-Self-Builders-Sustainable/dp/0857842285 https://www.amazon.com/Building-Straw-Bales-Self-Builders-Su...
- vxNsr 5y agoI read that straw is basically outlawed bec it’s hard to make a house with it and still be on the right side of fire safety codes. Especially if you’re using it as part of your insulation strategy.
- mercutio2 5y agoA straw bale wall burns MUCH more slowly than a stick frame wall. So this is really not accurate (and standard fire codes have accepted this). The bigger problem is that people don't like giving up so much of their footprint to 18-inch-thick walls.
- patrickk 5y agoWhere is it outlawed?
- baybal2 5y ago> Is there any research being done into alternatives that will scale to what we use concrete for? Flyash, and other pozzolanic industrial wastes. There are literally mountains of it. Problem? There is no "standard flyash," every power station uses a bit different fuel. Same for industrial wastes. Second option are natural geopolymers, but they are not that common, and coincidentally, most of countries with a lot of geopolymer deposits are rather rich, and that undercuts economic incentives.
- fomine3 5y agoI expect concretes win for wooden house with car vs concrete apartment with public transport.
- tromp 5y ago> For a German artwork, Time Pyramid, a concrete block will be placed every decade for 1,000 years. It will take 1200 years as the pyramid will have 120 blocks in layers of 8x8, 6x6, 4x4, and 2x2 [1]. [1] https://en.wikipedia.org/wiki/Time_Pyramid https://en.wikipedia.org/wiki/Time_Pyramid
- fredley 5y agoA lot of the problems with concrete are actually problems with steel reinforcement. Concrete alone is incredibly long-lived and durable, see the Pantheon in Rome. However steel rusts, expands and weakens within decades, even when you do everything right.
- silicon2401 5y agoWhy don't we just use concrete by itself? Is steel necessary for using concrete the way we do in modern times?
- namirez 5y agoBasically concrete is good only for compressive loads. Under tension it easily cracks. The steel reinforcement adds tensile strength to concrete.
- codeOnMaster 5y agoIn fact, the concrete MUST crack in the tension zone in order for the steel to take effect and provide tensile capacity to the member.
- kube-system 5y agoOnly if you don’t prestress the reinforcement. https://en.m.wikipedia.org/wiki/Prestressed_concrete https://en.m.wikipedia.org/wiki/Prestressed_concrete
- acchow 5y agoHow often are skyscrapers built using prestressed concrete?
- codeOnMaster 5y agoYes, steel is required. In the design of concrete structure, concrete is assumed to have zero (0) tensile strength.
- ginko 5y agoThey didn't even try to imagine it though. According to the linked article[1] there's about 1.1 Tt of concrete on the planet. At a density of 2.4t/m³ that's 458 billion m³ or 458km³. That'd be a cube of with a side length of 7.71km or about the height of Mount Jannu[2] from ocean level. [1] https://www.nature.com/articles/s41586-020-3010-5 https://www.nature.com/articles/s41586-020-3010-5 [2] https://en.wikipedia.org/wiki/Kumbhakarna_Mountain https://en.wikipedia.org/wiki/Kumbhakarna_Mountain
- phreeza 5y agoFor contrast, all human beings probably fit into a cube of 1km side length.
- koolba 5y agoThis is a classic xkcd “what if” topic: https://what-if.xkcd.com/8/ https://what-if.xkcd.com/8/
- baybal2 5y agoAnd with most of it being poured in the last 20 years in Asia. In China, people don't believe me that Americans live in wooden houses like they see in movies. Some think it's some kind of a set, or super-conspiracy by the party to render America in a bad light.
- capitainenemo 5y agoWhat's wrong with wooden houses? Easy to build, easy to insulate, in normal circumstances cheap. Far far better for the environment than concrete...
- lotsofpulp 5y agoIt is comical how so many seem to think wood and drywall is always inferior to concrete. I would even say it is the opposite, you are lucky to have access to cheap enough wood.
- bjt2n3904 5y agoI seem to remember reading this article from here: "The Most Effective Weapon on the Modern Battlefield is Concrete" https://mwi.usma.edu/effective-weapon-modern-battlefield-concrete/ https://mwi.usma.edu/effective-weapon-modern-battlefield-con...
- FredPret 5y agoMilitary strategy is ultimately about delivering your bullets to the enemy and putting a hard barrier between their bullets and your troops.
- azalemeth 5y agoThat was very interesting -- thank you. I do wonder what the locals thought about it all though. In my country planning laws are a big big deal!
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- sbierwagen 5y agoMost effective in CI warfare, maybe. Static defenses have historically not done well against tank armies.
- ars 5y ago"And if its rate of growth continues, it will overtake the total weight of Earth's biomass sometime around 2040." Rather than impress me with the amount of concrete, this actually impresses me with just how incredibly huge the biosphere is! That's an enormous amount of life.
- lmilcin 5y agoFun, useless fact: a single structure, Three Gorges Dam, has more concrete in it than half of all living people.
- jandrese 5y agoI'm pretty sure I have around 0% concrete in my body.
- bvoq 5y agoMini question: Isn’t there a lot of sand on the bottom of the oceans and we’re just running out of easily accessible sand?
- ddulaney 5y agoThere is! Lots of places already rely on marine sand, but extracting it has its own challenges and environmental issues. Lots of details here: https://worldoceanreview.com/en/wor-3/mineral-resources/deposits-and-markets/sand-gravel-and-phosphate-from-the-sea/ https://worldoceanreview.com/en/wor-3/mineral-resources/depo...
- bluGill 5y agoNeeds to be the right kind of sand. When your kids are playing at the beach you don't really notice that some sands are better for sand castles than others - and few could care if it was pointed out to them. When you want to make a building last though the properties of the sand matter.
- raptor99 5y agoThis just in! There is more rock on/in Earth with greater mass than trees and animals on Earth!
- aurizon 5y agoConcrete is a mixture of different sizes of a strong stone, like granite or silicate in a carefully graded mix of sizes from sand sizes upwards. The idea is to get the final block to be 100% stone(impossible) or as close as practical. You then cement this all together (mixing all the while) with powdered cement. Cement is a mixture of C3S: Alite (3CaO·SiO2); C2S: Belite (2CaO·SiO2); C3A: Tricalcium aluminate (3CaO·Al2O3) (historically, and still occasionally, called celite); C4AF: Brownmillerite (4CaO·Al2O3·Fe2O3). This is melted at high temperatures into 'clinker' (when melted it resembles lava from which classic roman cement was made as it collected as a fine volcanic ash). Rock has water of hydration strongly bound into, when melted into clinker the water evaporates = clinker. The clinker is ground to a powder and added to the graded mixture of sand and small rocks and water is added - it is then mixed very throughly and the final water ratio is established. It is then poured into the moulds that hold the cement in the final shape you want when it sets. You vibrate and shake well to get the air bubbles out and then you want for it to cure. As it cures the powdered clinker absorbs water and turns into the fully hydrated final (set) form. It can take months to fully set, but usually after a day it is into the 60-75% area of final strength. This makes heat = big things need active cooling, small stuff not so much. As it cures and very strong matrix of hydrated crystals fills all the space = set or cured concrete. Reinforcing can be any strong material that is not brittle. Usually steel rebar is OK for a dry life structure. For damper areas you can use epoxy coated rebar, then galvanized rebar, then epoxy coated and galvanized rebar. For the next stage stainless steel rebar is the high cost option. Nuclear power stations use SS rebar in some cases. Corrosion. Steel corrodes. Steel = FE,(1 atom) corroded steel = FeO (2 atoms = bigger) if oxygen reaches the steel it will make FeO - these 2 atoms are bigger than the one atom of Fe. This means the FeO will expand with an irrestible force (200 times as strong as concrete). It is this rebar expansion that makes huge cracks = more water in, = bigger cracks etc. FeO is as weak as kleenex as a support member. so as the concret and rebar turn into powder the strngth of the structure vanishes. At some point you get this sort of collapse - all of which was preventable by proper design and maintenance. Punishment? imprison them in the basement of one of their badly made buildings and let them spend their life waiting for the inevitable collapse. Concrete Wiki https://en.wikipedia.org/wiki/Cement https://en.wikipedia.org/wiki/Cement
- woleium 5y ago> If future archaeologists do the same for us, what material might they choose to define the 21st Century? Silicon? Plastic? Both are candidates, shaping the world for better and for worse. But if the decision were based on scale alone, then there can be only one answer: we are living in the age of concrete. lol, yes! the "plasticine". ;)
- euske 5y agoI just fancy this: is it possible to build a space elevator if we gathered all the concrete that is made so far?
- ragebol 5y agoNo. Concrete is good at compression, steel good at tension and reinforced concrete at both. A space elevator needs tension, a lot more than steel can withstand.