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How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues
- skybrian 2mo agoModern concrete has steel rebar, which is very useful, but eventually corrodes. Stainless steel rebar could be used if longevity mattered, but usually it doesn’t because the building will likely become functionally obsolete and need replacing before then.
- warumdarum 2mo agoYou could wouldnt even need that. https://de.wikipedia.org/wiki/Opferanode https://de.wikipedia.org/wiki/Opferanode
- eru 2mo agoYes, but you have to replace the sacrificial anode every so often. https://en.wikipedia.org/wiki/Galvanic_anode https://en.wikipedia.org/wiki/Galvanic_anode
- Barbing 2mo agoLike the plate of food on the grass for the bees at the barbecue
- eru 2mo agoMore for the wasps, I guess?
- beeforpork 2mo agoWasps, not bees. (Sorry, I'm a bit of a nerd. But I am sure you can cope with that.)
- jaapz 2mo agoWait, does this actually work?
- eru 2mo agoIt sure attracts the wasps. Whether you have less of them on your real food compared to the counterfactual, I don't know.
- Barbing 2mo agoJust wish I could claim credit. Decoy plate is essential. And since nobody complained it sounds wasteful, I suppose it should be able to be just scraps. May your next camping trip or picnic be wasp free!
- masklinn 2mo ago> Stainless steel rebar could be used There are also coated and non-metallic rebars.
- terribleperson 2mo agoCoated rebar could be good, but the coating can be damaged anywhere from manufacture to installation.
- masklinn 2mo agoYup, every alternative rebar has drawbacks which causes increased costs or different failure modes which is why they tend to be used in specialised applications where they are necessary.
- deleted 2mo ago[deleted]
- benj111 2mo agoDefine functionally obsolete. Ultimately most tall structures as a reinforced concrete skeleton with glass hung on the sides. It seems to me that as you're going to replace it with another basically identical concrete skeleton it makes sense to have that skeleton last as long as possible. And then refit that skeleton.
- smalltorch 2mo agoIt only corrodes if it's not completely encased in concrete. The concrete stops the reaction. And, if one portion of the rebar is not encased it will eventually corrode through overtime.
- adolph 2mo agoThis is something I wasn't aware of that is fascinating. The ph balance of the rebar's environment determines the progression of oxidation. There was a guy in the 1920's who observed this and had the idea to put cement in paint; it was so successful he renamed the company to cement spelled backwards. Inside the concrete, Ca(OH)₂, which is generated by the hydration of cement, creates a strongly alkaline environment, with a pH value of more than 12.7. In this environment, a passivation film forms on the surface of the rebar to prevent corrosion. However, the pH of the concrete decreases as micro-cracks develops and chloride from the outside infiltrates the rebar. Eventually, as the environment inside the concrete becomes neutralized, the corrosion of the rebar accelerates, which reduces the overall durability and stability of the reinforced concrete structure. https://www.sciencedirect.com/science/article/pii/S095006182503908X https://www.sciencedirect.com/science/article/pii/S095006182... A sighting of preserved steel reinforcing bars sticking out of old concrete rubble piqued the curiosity of our company founder, Albert C. Bean, Sr. After investigating this finding, his company, Armor Oil & Chemical Company, began producing a patented cement-filled coating formulation that, in its updated form, still protects structures from corrosion today. https://tnemec.com/about/ https://tnemec.com/about/
- simonebrunozzi 2mo agoA picture of one of these toilets would have been useful.
- defrost 2mo agohttps://www.science.org/cms/10.1126/sciadv.aeb0754/asset/924528ed-e829-41a5-8465-ac7c39db742b/assets/images/large/sciadv.aeb0754-f1.jpg https://www.science.org/cms/10.1126/sciadv.aeb0754/asset/924... From: https://www.science.org/doi/10.1126/sciadv.aeb0754 https://www.science.org/doi/10.1126/sciadv.aeb0754
- demosthanos 2mo agoRelated, Grady Hillhouse on the myth of Roman concrete. > The miracle of modern chemistry has given us a wide variety of admixtures like superplasticizers to improve the characteristics of concrete beyond a Roman engineer’s wildest dreams. So why does it seem that our concrete doesn’t last nearly as long as it should? It’s a complicated question, but one answer is economics. There’s a famous quote that says “Anyone can design a bridge that stands. It takes an engineer to build one that barely stands.” Just like the sculptors job is to chip away all the parts of the marble that don’t look like the subject, a structural engineer’s job is to take away all the extraneous parts of a structure that aren’t necessary to meet the design requirements. And lifespan is just one of the many criteria engineers must consider when designing concrete structures. Most infrastructure is paid for by taxes, and the cost of building to Roman standards is rarely impossible, but often beyond what the public would consider reasonable. https://practical.engineering/blog/2019/3/9/was-roman-concrete-better https://practical.engineering/blog/2019/3/9/was-roman-concre... A large part of why Roman concrete lasted longer than ours tends to is that we suffer from a shortage of narcissistic emperors with the means to wield entire economies towards their own immortality.
- seydor 2mo ago> we suffer from a shortage of narcissistic emperors not recently
- defrost 2mo agobut not ones willing to put the effort into properly fixing a pond.
- fragmede 2mo agoWho's pond? I'm willing to bet billionaires' estates have well tended ponds, contrary to public ponds. Or a reflecting pool.
- kQq9oHeAz6wLLS 2mo agoIf you're talking about the algae, it came back after Obama's $34m renovation, too. Turns out algae is hard to kill, especially when you feed the reflecting pool from a tidal basin.
- Mistletoe 2mo agoI’ve often wondered why every good sidewalk I see has a WPA stamp on it from the 1930s and the modern ones are all crumbled and uneven. https://share.gemini.google/5g0gxGyOmAPD https://share.gemini.google/5g0gxGyOmAPD
- defrost 2mo ago.. and, also, ... The folk of the 1930s were entirely capable of making poor quality concrete that barely lasted 30 years (source, my father, born 1935, still alive despite having mixed many a batch of concrete and having laboured). The reason you don't see that walking about is that poor quality 1930s concrete was replace 50+ years ago.
- TylerE 2mo agoSurvivorship bias in action.
- somenameforme 2mo agoI don't see how this would work because you're saying that the older sidewalks are scrapped and rebuilt when they hit a state of 'x' deterioration, so you only see > 'x' state ones. But how then could it be that newer sidewalks are allowed to fall below 'x' instead of also just being scrapped and rebuilt?
- altairprime 2mo agoMunicipal budgets cratered hard over the past couple decades, roadway maintenance is given precedence over sidewalk maintenance, and SUVs and electric vehicles do considerably more roadway damage per vehicle. So there’s concurrent causes promoting a global decay in sidewalk maintenance in cities that expanded without the necessary tax base to support maintenance: see for example Los Angeles (current-day example!) repaving all but one foot’s width of their roadways so that they don’t have to fix broken sidewalks. This doesn’t contradict the survivor bias point! If anything, it’ll accelerate it: you’re about to see just how many (or few) sidewalk squares survive the underspend. Citizen science, here we come!
- aizk 2mo agoThinking of the ww2 plane with holes meme right now.
- bombela 2mo ago> It turns out that another chemical reaction, known as carbonation, might also contribute to Roman concrete’s longevity. Roman concrete was made lime cement (calcium dioxide); which cures via carbonation (hardens with carbon oxide). And adding pozzolan to lime makes it hydrolic (hardens with water). Is it surprising that it can still carbonate some? Modern concrete has steel which rust and crack concrete. You can use fiberglass rebar for longevity, or build without rebar even, but that is more costly and and less efficient.
- deleted 2mo ago[deleted]
- litoE 2mo agoAs I understand it, concrete has excellent resistance to compression but fails easily on traction, while steel bars are exactly the opposite. That is why you put rebar in concrete: the steel handles the traction loads and the concrete handles the compression. This works well because both materials have similar coefficients of thermal expansion, so as the temperature changes they both expand and contract at the same rate. I suppose you can engineer fiberglass to have the same thermal expansion coefficient and use it to replace steel (assuming it is just as strong on traction). But how would you "build without rebar even"? Wouldn't your beams start cracking at the bottom, where they are subject to traction?
- aw1621107 2mo agoJust FYI, I think you're looking for "(in) tension" instead of "(on) traction".
- mikepurvis 2mo agoTo build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere. But it turns out that's pretty inconvenient; we really like doing dozens of feet of span for highway overpasses, building floors, and everything else. So we put rebar in all the concrete and just acknowledge that that means it has an absolute maximum lifespan of a century or two, and will certainly not last for millennia the way pure concrete in pure compression can. [1]: https://www.theartnewbie.com/blog/rome/roman-arch https://www.theartnewbie.com/blog/rome/roman-arch
- aiauthoritydev 2mo agoThe whole promise of engineering is not to build a bridge that stands but to build a bridge that barely stands. It is not a good idea to build a bridge that last 500 years. You likely destroyed valuable resources to build one. Build a bridge that lasts 100 years and save those resources. In 100 years the technology to build bridges improves so much that it is lot easier to build a new one. At least in most countries like India.
- matheusmoreira 2mo agoNobody is going to tear down old bridges and rebuild them at enormous costs just because technology changed. Some things can't or won't be redone and so it's worth it to build it to last and getting it right on the first try.
- dev_l1x_be 2mo agoThis is exactly what we did with houses, buildings. We had perfectly functional 100+ years old fully functional, gorgeous buildings and we replaced those with brutalist concrete/glass barely functional garbage.
- wbl 2mo agoThere are exactly 3 old buildings in Warsaw thanks to the Germans. Brutalism exists because a generation who grew up in rubble wanted solidity.
- otherme123 2mo agoIn Europe we have plenty of old buildings. The good ones (i.e. made by very wealthy people) tend to be decent, with a skew towards huge living rooms but tiny rooms. The cheaper ones are a mess to mantain: cold in winter, hot in summer, expensive to renovate (it could be more expensive to renovate than to build a new one), bad to no isolation, in my region terribly humid, usually too dark with minuscule windows for modern standards. With roman buildings that last 2000 thousand years we are looking at survivor bias. Near me there are some roman ruins from a (cheap and small) public bath that are barely distiguishable from a pile of bricks. The are some nearby pre-roman ruins in better shape.
- joshellington 2mo agoThere must be a better format and distribution method than this. Ideologically a strong brand name and domain, yet ads every two sentences. Even with ad blocking, there is constant aggressive attempts at attention. I propose the communal brain rot is less to do with short form video, and more to do with the everyday experience of trying to read something enlightening, tickle your curiosity - and be just absolutely fucking hammered with autoplay interstitials and 720x90 and 300x250 bullshit.
- hirako2000 2mo agoDo you pay for satisfy your curiosity? In fact, that institution is non profit and publicly funded, so what gives... Anyhow reading the piece with Brave showed me no ads whatsoever.
- Cthulhu_ 2mo agoThere is, the article links to a source, https://www.scientificamerican.com/article/how-a-1-900-year-old-latrine-helps-explain-why-roman-concrete-lasts/ https://www.scientificamerican.com/article/how-a-1-900-year-..., which you need a $5/month subscription for. I'm sure hidden in the links is a link to the paper, which you can pay to get the no-nonsense study. This is the third or fourth degree of scientific reporting; first is the paper, second is a news report, third is adult pop sci magazines, fourth is youth pop sci magazines. Pick your poison / preference.
- gaoqian2580 2mo agoThis is truly a great miracle
- iknownothow 2mo agoFor those not familiar, the secret ingredients are to do with the Lime Cycle [1]: 1) Quicklime/Slakedlime (Calcium Oxide, CaO) 2) Lime (Calcium Hydroxide, CaOH2) 3) Limestone (Calcium Carbonate, CaCO3) To keep it simple, typically you start with Quicklime (CaO) and after construction you end up with some mix of all three and after hundreds of years, the masonry transitions to mostly Limestone with microscopic traces of the other two. The slow transition of the lime cycle upon exposure of the masonry to both air and water (rain) ends up making the structure "self healing" and "stronger over time". Fun fact! Lime putty is anti-mold even in humid conditions because upon exposure to moisture, CaOH2 + H20 becomes too basic for mold to grow on. Cement/Concrete (based on Portland cement) is water proof but Lime by itself is not. But Roman Concrete, made from Lime and mixing with ash or broken pottery or ceramics makes it water proof [2]. I beleive Roman concrete was used whenever contact with water was expected. Both concrete and Roman concrete have the same underlying chemistry (Pozzolanic reaction) to make them water proof [3]. The fascinating thing is that Lime is everywhere in ancient masonry. Lime is more breathable, workable and sustainable. The only thing is, it requires maintainance, which is why Portland cement has taken over the world. Modern cement/concrete is amazing for large structures. I hope Lime makes a comeback soon at least partly as putty and for building smaller homes. [1] https://en.wikipedia.org/wiki/Lime_(material) https://en.wikipedia.org/wiki/Lime_(material) [2] https://en.wikipedia.org/wiki/Roman_concrete https://en.wikipedia.org/wiki/Roman_concrete [3] https://en.wikipedia.org/wiki/Pozzolanic_activity#Reaction https://en.wikipedia.org/wiki/Pozzolanic_activity#Reaction
- iknownothow 2mo agoI forgot another important reason why Portland cement is preferred over lime these days. Lime takes a while to set (a few days?), cement sets faster.
- cm2187 2mo agoI am glad the pantheon still stands. But the real question is are there really any modern structure that will be worth preserving for 2000 years. Architects have long abandoned aiming for beauty to aim for originality. Originality doesn’t last. Humans in 2000 years will only wonder why on earth our society could manufacture atom level micro ships but couldn’t come with a single structure worth preserving.
- graemep 2mo agoThere are some structures worth preserving. Sagrada Família is one. Places of worship and private homes (at least those individually architect designed vs standard designs) tend to be a lot nicer than office blocks and other commercial places. I do think a lot of new building hideous. Looking at St Paul's in London from the west so you see the hideous backdrop to its east is depressing.
- fhub 2mo agoSydney Opera house comes to mind as something that might still be curious to people in 1000 years.
- cm2187 2mo agoA curiosity is one thing. But where is the wow factor you get when you enter Rome’s pantheon?
- ChrisRR 2mo agoWhat makes you think buildings aren't going to change within the next 2000 years? Hell just look at all of the Tudor buildings dotted around. They probably didn't think they were anything special 600 years ago
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- Saline9515 2mo agoSand used to make concrete is a finite ressource, and extremely polluting to extract. Why wouldn't we save it and build lasting buildings?
- metalman 2mo agocorrosion of rebar is so significant that there are specs for the acidity of rock used for agregate in the concrete. Older rock that has been "washed" by billions of years of water permiating it , is then used, fetching a premium. Look into it and there are periability numbers for everything, which is how water has gained it's reputation as the universal solven, and granite, hard as it is, is also a bit of a sponge. What is harder to figure is the use of a lot of carbon in rebar, which makes it harder and with a higher tensile stength, but with greater rates of corrosion, somehow the calculation is to not use an ultra low carbon steel with some nickle and larger cross sections along with low acid chemistry in the concrete.
- baybal2 2mo ago[dead]
- middayc 2mo agoVery interestin discussion below/above. I just want to say that building with hempcrete, which relies on lime and NHL (natural hydraulic lime) or Baumit Trassitplus whic is some version of roman "cement" relies on may of these principles and is a "modern building technique". It's also much more carbon neutral than many other methods, can produce good thermal dynamics and "breathable" walls. And is DIY friendly.
- dlubarov 2mo agoCompared to traditional concrete, isn't hempcrete much weaker and less rigid? It's an interesting material for sure, but I thought it was basically considered non-structural filler. Autoclaved aerated concrete is worth a mention as well - it's also a decent insulator and somewhat environmentally friendly, while additionally being, light, easy to cut, and somewhat usable as a structural element.
- ajwin 2mo agoA lot of the reason why concrete structures have failed so quickly is that the material was still fairly new when most of the structures failing now were created. There’s nothing that says that well designed and constructed modern high performance polymer modified concretes will have the same problems. They also have additives like zypex paste that make it more waterproof and self healing. They also have permeable formwork liners for increasing the surface density of the concrete and chemical concrete hardeners etc.
- folbec 2mo ago"A lot of the reason why concrete structures have failed so quickly is that the material was still fairly new when most of the structures failing now were created." Or the designer can get too creative : https://edition.cnn.com/2025/05/15/style/432-park-avenue-skyscraper-lawsuit https://edition.cnn.com/2025/05/15/style/432-park-avenue-sky...
- eleveriven 2mo agoYet carbonation is not universally helpful
- vfdkdjjckx 2mo agoNothing is universally helpful in the most extreme hypothetical.
- rewtraw 2mo agowe can't figure out roman concrete we don't know how ancient megaliths were built centuries old cathedrals and holy places have more intricate masonry and carvings than anything built today (with allegedly more primitive tech) are historians retarded? what's going on here? time is flowing backwards and civilization is declining, but humanity is under a collective trance and can't even see it.
- andsoitis 2mo ago> time is flowing backwards and civilization is declining Why do you think civilization is declining?
- rewtraw 2mo agoyou can see it clearly in architecture alone. cathedrals and other ancient constructions are far more impressive than what we build today - they obviously had more prosperity and will for greatness than modern man. and it doesn't take much of a leap to understand the people who built them were more advanced than officialdom gives them credit for. we are in a period of soullessness, and while we have made technological strides - and are probably in a needed period of materialism to make these strides - in order to move back 'forward' in time we need to integrate both the material and spiritual. tldr: Kali Yuga doing its thing
- 0xbadcafebee 2mo agoA lot of comments here on Roman concrete are missing the killer application: marine use. Any other concrete we know of will degrade in seawater due to different failure modes acting at once (leaching minerals, pH imbalance, freeze-thaw cycles), and none have the same extent of self-healing. Roman concrete (pozollanic material, quicklime, seawater) is the only one that resists all failure modes and will sit in the ocean happily for millennia. The main downsides are it's not very strong, it takes a long time to cure, and volcanic ash is hard to come by. The specific of ash you use changes the result, ash is not always that easy to get, and Neapolitan Volcanic ash just happens to be extremely effective at this application. There are alternatives you can make today. You can make Roman concrete today, but it's still kind of tricky and has the aforementioned downsides. Fly-ash concrete is like volcanic ash concrete but still not as good, and we're gonna run out of fly-ash as coal mines close. High-slag concrete works well but will degrade over time. Alkali-activated concrete is really promising as a Roman concrete alternative but doesn't have long-term test data. Ultra-high-performance concrete is brittle and won't self-heal. So in truth we still don't know everything about Roman concrete and we still can't make its equivalent without traveling to southern Italy.
- flippyhead 2mo agoI heard once that if the Roman civilization had continued, the state of current technology would be something like 500 years more advanced. I don't know if I ever believed it, but sometimes I do.
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- carabiner 2mo agocan we not do this
- daft_pink 2mo agoIs anyone else wondering why their house isn’t made of Roman Concrete everytime they read a story like this.
- happyopossum 2mo agoNobody wants to pay for a house that would take a year to build, with multiple 30 day work stoppages for concrete curing….
- penguin_booze 2mo agoImagine how it'd be if BigConcrete were to make concrete. Every year at ConcreteCon, yet another release that lasts for... one year!
- SoftTalker 2mo agoSurvivorship bias? The only Roman Concrete we see today is the stuff that has lasted.
- dukeofdoom 2mo agoHow do we know Egyptian pyramids were not build from a form of concrete?
- thekid314 2mo agoBecause they are solid stone carved from the mountains south of Cairo, near modern day Helwan.