In an earlier thread someone working in the industry said that today the cement producers can make arbitrarily sturdy concrete, but almost no one wants to pay for the top-tier stuff.
Part of it nearsighted thinking, the other part is consideration that money could be spent on like nicer decor, or maybe build larger number of 100 year buildings than a smaller number of 1000 year buildings.
If the choice is between using the money for one building that lasts 1000 years or 10 buildings that last 100 years, each, I'd pick the ten buildings, too. There will be new considerations anyway. Like cables, which weren't a thing 500 years ago. Or water pipes. Who knows what else we will want to put in our buildings, that are easier done with building something new than updating something old.
Regular concrete can last for 100 years and who knows how design /needs can change during that so it makes sense not to build with much more expensive 500 year concrete.
Isn’t it the height of hubris to believe we could plan 100 years ahead? What cities haven’t radically changed in the last 100 years, with nearly everything being replaced with something better than they could have conceived of?
> What cities haven’t radically changed in the last 100 years, with nearly everything being replaced with something better than they could have conceived of?
You’d be surprised. Almost all of the German cities were destroyed in WW2 (meaning their downtown area). The same goes for Polish cities, or further East cities like Kiev, Odessa or Kharkiv. WW2 was also quite brutal for Western cities like Rotterdam or London. WW1 obliterated most of the cities in Northern France and South-West Belgium. The streets of Madrid saw active and intense fighting in the Spanish Civil War. And many of the cities that escaped the wars relatively unscathed had to contend with the modernist movement of the 1960s and the 1970s, which saw many interesting buildings demolished because they didn’t look modern or functional enough (Athens being a prime example for this).
Buildings and roads are technologies that have existed for thousands of years, and may continue to exist for thousands of years. If you want to protect people and things from the world, it's hard to do better than walls and a roof. If you want to get from point A to point B by land, it's hard to do better than a network of cleared spaces. Sure, we may not know exactly what people in 100 years will want, but it's likely they'll still want buildings and roads.
I get the point you're trying to make but 100 years is not a long time-scale for construction projects a bit larger than a single-family home. I think expecting the foundations and the facade of a building to last 200-300 years is reasonable.
I've lived a large part of my life in a house that is about a hundred years old. The house I'm currently living in is about sixty years old. That's really not a long time in the life of a city.
I suspect monuments are the only thing that benefit from longevity.
I was imaginging government buildings built for 100 years, but I figure climate control and window design has radically changed and older buildings are probably uncomfortable in these ways without retrofitting.
There's another ancient building technique that doesn't get considered in the modern era: cutting and moving gigantic 10-ton blocks of stone. Sure, it's expensive to cut and move, but a bunch of dudes with rickety boats did it across huge expanses of land and water, and their structures also still stand today.
If the carbon footprint is a concern, it might be a perfect opportunity to propose alternatives to the carbon-intense techniques we've adopted. For example, William Fairbairn invented a hand-powered crane, whose 642-to-1 ratio meant two men turning cranks could lift 60 tons. Our land and water-born vessels could also probably be innovated on with similar efficiency, if it wasn't so damn easy to burn ancient vegetation.
If time isn't an issue, those techniques all are fine and are proven to work.
Sadly, time IS an issue today, so 2 men on a paddle won't build the hoover dam.
Even if they could.
Are you claiming that construction today is fast? I don’t understand.
Are you claiming that a contemporary construction project would be able to build the Hoover Dam? That was almost 100 years ago and a lot of things have changed...
Well, imagine how much knowledge gets lost through the ages. If there aren't contemporary specialists who value or have enough time to study a technology or a cultural work, it could eventually just disappear. Add to that that different ages and societies build and create from different frameworks, then its conceivable that there are valuable pieces of information that our current society may never uncover or discover, just by virtue of working within a completely different context.
Yeah. It is a mistake to believe that technology can only progress forward. If a generation dies without passing on certain knowledge, it's lost and has to be rediscovered the hard way, and that can certainly happen to technological know-how just like anything else.
It is surprising how easy that can happen. I returned to a client to help with the next generation of a product they were developing. I helpwd with the S/W for the earlier generation. The people working on it when I returned had the source code but none of the supporting documentation. The documentation wasn't extensive and without my help, it might have been difficult to understand anyway. (Or maybe I underestimate the folks working on it at the time.) The bigger problem was that they had no idea what was missing, let alone where to find it. Much of it included descriptions of why things were done the way they were.
On my return, I knew what was missing but had no idea where it was. In the ensuing decade, the company had been through three generations of documentation archives and I had to ask to get access to anything in the new system. I didn't know what to ask for. Further, they gave me a new login and could not provide access to my old email account. (Much of the documentation was shared via email attachments.)
I got lucky and ran across another engineer who had worked on the project and had saved a bunch of stuff. He was now with IT, had helped with the document migration and knew where I could find it. I found that a pretty tenuous way to propogate technical history.
That was over a ten year period and many of the participants were still alive and working there. Any break in the chain and they would have had to start the next generation from existing code and the embedded comments (which would be cryptic if you didn't understand how and why the system worked the way it did.)
I'm just thinking right now about how we have terrible knowledge silos at work and how screwed we'd be if these people won the lottery. I'm pretty sure NASA had the same problem and we can't rebuild a Saturn V even if we wanted to. Didn't we also forget how to build nuclear bombs or something?
No, sadly there's money in building nuclear bombs. But we might be at risk of losing track of where the nuclear waste is, and how to keep track of it. So here's the standard for that:
> jbay808: * If a generation dies without passing on certain knowledge, it's lost and has to be rediscovered the hard way, and that can certainly happen to technological know-how just like anything else. *
> cbanek: Building the next [Saturn V] would be really hard
Leading edge technology isn't known by that many people to begin with, so it's easier to lose. Even though the organization that built Saturn V rockets was huge and lasted several years, there are still details that will take, as I understand it, a bit of archaeology to get at. If a technique doesn't become routine, can technology be said to have progressed up to that technique?
I'm not an expert, but from what I understand, the hard part wouldn't be the cutting edge rocket science (choice of fuels, valve design, etc) but the fabrication techniques.
The 1960s had a generation of highly skilled welders, machinists, and sheet metal workers that had honed their craft in the factories of the second world war. The USA today doesn't seem to have the same quantity of skilled workers and NASA has to design parts differently to allow automated tools to do the work.
But those fabrication techniques probably would have been considered routine at the time, although maybe above-average in complexity. So even a routine technology can be, in a sense, lost if it falls out of demand.
Yup that's what curious droid's video on this is saying as well [1]. Basically the plans all were off a little bit and each rocket engine was hand-tailored to the demands of the individual rocket by these skilled people you mentioned. They did document their changes but only on scrap notes that since were lost. The plans themselves that were archived don't contain those notes and even if they had them, you couldn't find people with such skills any more.
that is a little funny you're right. It reminds me of something interesting I read, don't know if it's true or not. I heard that in the "middle ages" (or dark ages) it was taken for granted that the ancients -- meaning the Greeks and maybe even the Romans, not sure -- had been way wiser and more knowledgeable than them. (You know, as they read Euclid's elements and Socrates and stuff.) As I remember it, all the way through the Renaissance that was the thinking, that the ancients had known way more.
Imagine thinking that the ancients knew more than we ever will, and trying to study their works to get at just some of the wisdom they had held. I think few if any people read ancient authors that way today.
There was this excellent video about the misconception that technology and knowledge advances over time.
It does not. It fades, gets lost. Where are the Steve Wozniaks and bill gates? Where are the people truely understanding this stuff. Where are the people who can optimize code like back in the days?
I think you are conflating the notion that, at a given time slice, a majority of the popular sentiment about the future may not have always been positive, with your own opinions of modern engineering.
For vast swaths of human mind, popular opinion tended to see the future as bleak and the past as filled with greater men, accomplishments, etc - the good days are behind us. Post industrial revolution thinking and adoption of science has mostly changed that opinion to hope - the good days are ahead of us.
As for people who can optimize code like back in the day: I am not sure where you work, but I bet if you look at the best engineers in the best tech companies today (google/ Facebook / Netflix / amazon / Uber / palantir) you’ll find a lot to be impressed with.
I think it is more about why it works than how they did it. It’s probably going to be a challenge to apply that knowledge to a modern process that produces the quantity of concrete we need today.
Or it might be the case that now that we know that they needed volcanic ash we are going to figure out a way to produce that stuff at industrial scale and pump tons and tons of it.
In case anyone mistakes this for a summary of the article, here's what it actually says:
> Modern cement mixtures tend to erode, particularly in the presence of seawater, but the Roman recipe of volcanic ash, lime, seawater and a mineral called aluminium tobermorite actually reinforces the concrete and prevents cracks from expanding, researchers found.
If your building site never has earthquakes, that can work well. Otherwise an earthquake might put some part of the structure under tension and cause it to fail.
The solution to that is to build it bigger with a wider footprint. Obviously this is an expensive way to build, but if you engineer it right (and throw enough concrete at it) you can create structures with nearly arbitrary shake resistance.
(Think of how hard you'd have to shake the Great Pyramid of Giza to make it collapse. That's not concrete obviously, but it too is under compression almost entirely, except for the corbel and lintel ceilings. The proper arches used in Roman concrete construction show that with the right engineering you can push unreinforced concrete pretty damn far. The Pantheon is probably the most impressive example of it. Compare how well it's withstood earthquakes with the Colosseum.)
The reason why the Collosseum fell is that everybody removed it's lead rebar because it was worth money when Rome fell--without that lead rebar in the joints, every earthquake knocked a bit more off the building.
The Romans lived in an active fault zone and understood building to survive earthquakes.
Over hundreds of years...it can't. The question remains, how long does that time span extend? 200 years? 300? A millenia? Could the Brooklyn or Ben Franklin Bridge last that long? Even the next 70 or so?
What’s way stranger to me is that aluminum does not have an endurance limit (for non-Mech E’s, this is worse for aluminum even though it sounds like it might be better).
Basically, there is no deformation so miniscule that it lasts forever. It just affects how many cycles/how long it takes. Steel however, if you deform it only very little, lasts practically forever. You just need to design it to not deform too much at normal operation.
Incidentally, this fatigue vs. approaching the strength limit issue is why airplanes have limited flights. The fuselage/hull is made to last long enough, but not necessarily do well longer than that.
In my part of the country there are mostly concrete bridges. My father in law started his construction career at a bridge building company. A lot of concrete bridge spans are hollow with styrofoam inside. It would be too heavy if it was solid.
You're probably joking, but since "it's just survivor bias" is a popular take these days, I'll respond as though you're serious.
A bridge that stands for 2000 years without (much) maintenance isn't survivor bias, it's disruptive technology.
Yes, we only see the best of Roman architecture, and most Romans probably lived in wooden shacks or stone apartments that have long since crumbled or been demolished.
But Roman concrete is chemically different than the Portland cement that was invented in the 1800s, and although there's certainly a distribution of building quality and workmanship that will result in a wide spread of lifetimes, we don't have any reason to expect that any concrete building built from Portland cement and exposed to the elements like Roman seawalls were will last 2,000 years. The distribution just doesn't have that long of a tail to it.
An important component to the survivor bias argument in this case is: we have no way of knowing what roman concrete didn’t survive. Maybe the ones standing are atypical, or were in some way a fluke as opposed to the marvel they seem to be.
When we see these structures standing, our reaction should be "wow! How did they do that? What can we learn?"
Not "well, I bet they also built a lot of bad buildings too; nothing to see here".
When you build something twice as good as the average, it's a fluke. When you build something 20x as good as average, it's worthy of study. Even if these are atypically good examples of Roman architecture[1], you can't pull off the moon landings by launching a ton of backyard fireworks and hoping for a long-tailed success distribution.
The best buildings represent the state of the art of the best architects and the best masons working with access to quality materials and an adequate budget and timeline. Not dumb luck and guesswork paying off.
[1] Which there are decent reasons to not expect. For example, we know that many Roman buildings were demolished deliberately by later generations because they weren't Christian enough, rather than because they collapsed.
Sure, surviving for such a long time is a big accomplishment but compared to bridges today, they are relatively short bridges that cost more to build and allows less load. What is there to research other than figuring out how they work? They are well structured blocks of rocks that distributes the load well basically.
How they were built is probably more interesting, but still would be useless
> They are well structured blocks of rocks that distributes the load well basically
So is a building like the Burj Dubai, but this is an incredible understatement of the technology involved. The reason Roman concrete is interesting is that until ~50 years ago we had no idea what made it so durable. Dams are being built using these discoveries, sounds quite useful to me.
As the article explains, the most interesting thing is their seaworthy cement. Although today's Portland cement is newer, it wasn't adopted because it was superior to Roman cement, but because (until recently?) no living person knew how to make Roman cement.
Hence, we can indeed learn something by studying it.
It's typically not the case that we can't make things as well as we use to. It's just that we've found ways to make them that are cheaper by an order of magnitude and last just long enough to do their job.
Roman concrete wasn't disruptive. It was disrupted.
> Roman concrete wasn't disruptive. It was disrupted.
I'm amazed by this mentality. It's like the very possibly of a technology being forgotten, rather than surpassed, is axiomatically impossible.
If "everyone who knew the recipe died" counts as getting disrupted, then yes, it was disrupted. And if Roman concrete counts as more expensive because the supply is literally zero, the yes, modern concrete can be seen as cheaper.
But understand that modern Portland cement wasn't invented to improve on Roman concrete, but rather as an attempt to replicate it, because nobody until then had any guess.
That's not my mentality at all. I understand technology can be lost and forgotten.
In this case, I actually think the naive mindset is the one that assumes, more durable is better. No, more durable is more durable. Is static typing "better" than dynamic typing? No, it's a different tool for a different task.
Please don't fall for clickbait. It sounds so cool to have lost a technology over time, and it certainly is possible, but I don't think that's what happened here.
1) This certainly doesn't imply that Roman concrete was discarded because a more cost effective formula came along. The fact is that it was lost to civilization for over a thousand years, and then Portland cement was discovered. There was no period of time in which a contractor could choose one or the other and selected Portland cement for price or performance reasons. So beyond a doubt the Roman technology was lost.
2) That article is pretty unconvincing, being basically just a blog post by a cement guy who points out the same things that anyone else should already expect, all of which were mentioned in the comments section here. And not only because the author misspelled Raman spectroscopy.
3) Survivor bias has been addressed in several other comments. It's a valid point if someone points to a 2,000 year old bridge and says "my building needed repairs after just 10 years; clearly no Roman buildings ever had that problem". Yes, I'm sure the Romans also built buildings that fell apart within 10 years and needed repairs. Those bridges don't say anything about the quality floor. But that's really missing the point.
The quality ceiling is also not an accident which is my point about the moon landings. Most rockets launched in the 20th century were backyard fireworks, so you could point to the moon landings as "survivorship bias that doesn't reflect the crude state of 20th century rocketry in which most rockets were just backyard fireworks and few even made it to space, we just only remember the ones that did".
But that statement, while true, also makes it sound like the moon landings were a statistical fluke in which a bunch of people who had no idea what they were doing got lucky and lauched some fireworks that made it to the moon. That would just be wrong. Likewise the best Roman buildings were not built by luck, but by skilled engineers with large budgets, and they are just as impressive as they seem. It's no coincidence that the structures that survive are high budget state infrastructure projects, government and religious buildings, and estates of exquisite craftsmanship, and not random commoners' houses, even though there were probably 10,000 houses for every aqueduct.
Survivorship bias also doesn't mean there's nothing to learn from those materials. Probably not every batch of Roman concrete was perfectly formulated to perform optimally, but that's no reason not to study the surviving samples and note their impressive durability.
Randomness isn't everywhere. If you dump a thousand ball bearings in the ocean and pull them up ten years later, you expect to see a thousand rusty ball bearings. If one of them is somehow still smooth and polished, you don't conclude that erosion just acts randomly and it's survivor bias. Instead, you should look closer and see if maybe that one was actually made of 316 stainless or something.
I agree with you on survivorship bias. I by no means think it's random chance that these structures survived.
All I take issue with is treating these as anything more than "impressive for their time". There isn't some secret to emulate here, and we are not incapable of building structures that would stand a similar test of time. That whole part is silly clickbait.
I agree that we could build 2,000 year structures when we intend to. I wouldn't be surprised if some of our nation-scale works like the Hoover Dam last that long. The Long Now foundation is even trying to build something that lasts for 10,000 years.
But I disagree that there's no secret to be discovered in Roman concrete. Materials science involves a lot of guess-and-test work and luck, and there's no harm in exploring whether the ancients might have had better luck with some of their guesses.
We have some ideas. For one thing a reasonable amount of documentation still exists that speaks how things where run.
Rome was not building all that much stuff, they simply didn’t have nearly the population or wealth we do. Think the population of Tanzania and the GDP of Libya spread across as much land as India.
Meanwhile we can see structures like Portus Adurni that are mostly intact. A meaningful percentage of their larger structures are still around.
And after the fall of Rome the economy was smaller and more fragmented.
Last time I looked into this I came away with the observation that preindustrial concrete was very labor intensive. We use it for it's physical properties and because it's 'cheap'. Roman concrete wasn't cheap at all.
The central Roman government was able to marshal the effort necessary to produce it on a ongoing basis for particular uses. But I understand Romans mostly used brick and mortar for ordinary construction.
After the Roman Empire fell apart concrete probably didn't make sense.
Eh, we kind of do. If the surviving structures were that far off on the long tail distribution, then we could anticipate that there were truly massive amounts of concrete structures in existence before. And we can tell from other things we know about Rome whether that was the case (it’s not).
We still use Roman technology or ideas today: double roman roof tiles, underfloor heating, water distribution, paved roads etc. Italian ceramic tiles, stone and adhesives for them are still the best you can get in Europe.
My 10 year old building is just about to do a massive patch-and-seal job. Developer put the rebar too close to the surface, then evaded all attempts to get them to pay for it.
2013: https://news.ycombinator.com/item?id=5883443