I think 50 years is a very pessimistic (and journalistic) value. There are whole towns in eastern europe build with reinforced concrete and they are still ok.
They often aren’t OK. In many of those whole towns in Eastern Europe, the municipality is gradually pushing to move people out of the socialist-era concrete buildings and into newer ones. Their design means that, even if the structure itself does remain physically sound, they often struggle with ventilation, so mold forms.
That’s not universally true. In my home city the socialist-era blocks tend to be the ones without mould, when compared to some of the under-regulated new builds. If anything they’re sought after.
This seems to be mostly a construction quality issue of the time - in my corner of Eastern Europe, the 1960s buildings often are so bad to need reconstruction or replacement, but the 1900s/1910s/1920s/1930s buildings are structurally fine (with some exceptions due to total neglect) despite being twice as old. It's more of an indicator if you intentionally build mass cheap sloppy housing intended to be temporary just to allow faster urbanization ASAP (as arguably was the goal of 1960s soviet housing projects), then you're not getting proper long-term buildings - IIRC it was expected already when being built, the planned design lifetime of those buildings without major repair was just 30 years or so, and they've certainly met that bar.
That seems super unlikely to be true. Easy counterexample: the Ingalls building in Manhattan was the first skyscraper to be built out of reinforced concrete and it was built in 1903. It still stands today.
It's been maintained with constant supervision. Probably regular inspections and fixes. Watch what happens in as little as ten years once it has no human intervention at all.
The eli15 answer is that concrete is repaired by excising the damage and replacing what was removed. If you're really interested check out Sikas brochures.0 if you prefer video form I found this [1] that seems to cover a good variety of applications and can probably be comfortably watched at 2x speed.
Maintaining concrete is a matter of having routine structural inspectors come out to poke and prod the concrete. Worn traffic areas get patches and sealants. Areas with a lot of runoff get seals to direct water in ideal ways. Etc.
plugging/checking for holes in the roof so there's no water infiltration in the walls (water in the wall will quickly degrade them, especially if temperatures to freezing levels)
Pretty much. Water is the enemy of any construction.
A farm near where I grew up had a big barn, built in the 1700s that was in daily use until the mid 80s. Due to a family/inheritance dispute, maintenance ceased in the 90s. At some point, the roof leaked and that set in motion things that resulted in collapse last year.
This can be the period the construction engineers are responsible or the worst possible exploitation conditions. My estimate is 200 - 300 years if roof is maintained well and no pipe leaks inside.
Worst possible conditions usually involve seawater, acidic conditions, and/or moisture. Even without those factors it’s rare for reinforced concrete to last more than 50 years. The more protection from the elements, the better of course.
Most concrete structures with long design lifetimes made of concrete (some dams, levees, bridges - but not all by any stretch) will use design techniques to minimize or remove the use of rebar, such as compression only designs , or ‘overbuilding’ so expected corrosion still leaves the structure strong enough over it’s design life.
Generally, concrete is a strongly base compound and protects rebar from corrosion. Over time however it can be influenced by the environment, with those base compounds reacting and leaving a less protective environment. Some environments do it faster than others.
If the covering concrete is strong enough/thick enough, the pressure caused by the rebar turning to rust inside the concrete won’t crack it - if the rebar was structurally important (pretty much always or why use it?) it still weakens the structure though, sometimes dangerously.
Attempts to mitigate the risk where weatherproofing is not an option and rebar is essential for structural reasons like concrete roadways and bridges have had their share of disasters. epoxy coated rebar for instance can lead to unpredictable and sometimes rapid failures in exactly the types of environments it was expected to help in [https://www.fhwa.dot.gov/publications/publicroads/99novdec/r...]
The more dependent a design is on an element that can corrode, and the tighter it’s design tolerances, the more fragile it is. The more overbuilt it is, and more conservative the design, the more expensive it is.
Yeah, German reinforced concrete structures like those and the flak towers are basically gonna last longer than the pyramids. They are the honey badger of architecture.
Uh no, axis and allies produced the cheapest/most effective means to win the war. Take for instance the Stg44, mostly stamped sheet metal. Russian PPSH, stamped sheet metal.
I think GP was trying to say that fortified buildings last longer than shoddy McMansions. Which seems true given the survival ratio of castles to hovels over a millennium or so. Of course to win a war you may want to fortify cheaply... but given the modern system armies we have now I’d have to say that part of the grand strategy is to simply outspend rival nations.
Apparently it depends on the climate. In Singapore, you need to maintain the surface of the concrete to keep water out or the rebar corrodes and the concrete spalls.
Buildings only last 50 years or so before being torn down and rebuilt.
It doesn't depend on the climate, but it does depend on the concrete chemistry (that does vary geographically).
Anyway, the sequence is that micro cracks form on the concrete and expose the steel, then the exposed steel rusts and pushes more concrete away, exposing more steel. This too can be fixed before it becomes a problem.
I think the material point is that, as engineers, we have to all concede that modern concrete has that fatal flaw. People are being hyperbolic here when they are saying these buildings won't last 60 years. In my opinion, most will definitely last 60 years, even with no maintenance. At the same time, I'm intellectually honest enough to concede that few reinforced concrete structures will last 500 years with no maintenance. And I'm confident that zero reinforced structures will last 1000 without maintenance.
People on this thread claiming a collapse in 60 years are probably not civil engineers. People claiming that reinforced structures will outlast the Pyramids at Giza are definitely not civil engineers.
Oh, agreed. Concrete itself is not a completely stable chemical compost. Modern civilization is not creating many structures that have a chance of surviving for centuries.
What I don't agree is on the classification of that as a "fatal flaw". Looks like we are in serious disagreement on the goal of our constructions.
Carbonation is another factor – fresh concrete is contains calcium hydroxide and is therefore an alkaline environment, which has the effect of protecting the rebar from corroding.
Over time however, carbon dioxide from the atmosphere slowly seeps into the concrete (anything that's only intermittently wet fares the worst here), turning the calcium hydroxide into calcium carbonate. While this has the beneficial side effect of actually increasing the strength of the concrete itself, it also lowers its pH value, which means the rebar is no longer protected against corrosion once the carbonation process reaches the rebar.
This was an interesting read, but it was written mostly as if cities were just surrendered to the forces of nature. In many or most cases, I would assume that when a building starts to succumb to the forces of nature, the city would either reinforce it or demolish it, and the city itself will continue to evolve. In some cases, I supposed cities may be abandoned, but in most cases, it will probably be a slow, evolving change barring some dramatic catastrophe.
Some cities, yes. Jakarta comes to mind as a likely example. But if you look at photos of the areas of Jakarta that are submerged in water, it's clear that they weren't wealthy areas to begin with. I think wealthier cities like Shanghai or Miami will take a very different route.
In some places - Detroit is an example - people start leaving, the tax base dwindles, and by the time they realize the need to demolish things, the funds aren't there. In some cases, the city pulls in its borders and declares the former-city areas someone else's problem.
I think the poor quality of the U.S. housing stock reflects the long-term shabbiness of our mandatory nomadic character. We move for the jobs, we set up shacks by the gold mines, but we never develop roots and, for the most part, we never get to build real wealth.
Why do you think US houses are of poor quality? Just because they don't last forever with no maintenance? I don't think there's any point in over-building.
It's also a strange statement because US housing is highly regional; there are no bungalow courts in New York as there are no brownstones in LA.
I don't think that's a totally unfair statement depending on the region though. At least in Seattle a fair amount of homes are Craftsman homes which haven't aged well since they were ordered directly from a Sears catalog without considering the very wet local climate of the Northwest. (And yes, that Sears and that Craftsman.)
I'm aware of Sears catalog homes but not of any link between the Sears owned Craftsman tool brand and the craftsman style of home, which is connected to the Arts and Crafts design movement. Can you provide a reference?
I do wonder if the tool name (apparently a brand purchased from a small Chicago toolmaker by Sears in 1927) was inspired in part by the architectural movement, which was the product of a specific designer (Gustav Stickley) in the early 1900s.
I couldn't find any references to such a connection though.
Buildings are alive like flames. They are living manifestations of a culture.
The Cathedrals stand because they have been maintained by each generation -- and each generation has added something: a chapel, a statue, a ceiling boss. To this day you will often find them surrounded by scaffolding. It detracts from the view but it's as much a part of the process as the stone.
Angkor Wat is no older, yet it has crumbled. Its maintenance ceased for generations. The difference is stark.
(Angkor is now seeing something of a revival. Restoration work has occurred over the last two or three generations, and more will happen now as the Khmer people become wealthier again.)
These buildings are a reminder that there are long-term dynamics of birth and death and reproduction that outlive the individual.
Countries fixate their national pride on what they have.
If they don't have the dynamism, economy, or youth of other countries, they fixate on what they do have — buildings which are faded memories of the cultures which built them.
I always wondered how you go from a thriving city to an 'ancient ruin'. A lot of cities in India have been continuously occupied for over 2000 years (Kalyan, Ujjain, Bharuch, Patna). A lot of them don't have any obvious ruins from that era (most old buildings tend to be from the medieval era or rock cut caves/temples/monasteries that were forgotten about in later eras) compared to a place like Hampi or Angkor (although both cities were abandoned in the medieval era).
My guess is that for a city to have relatively well preserved ruins, it has to be completely abandoned due to some calamity. If a city is continuously occupied, old buildings get incrementally replaced by newer buildings, and very few old buildings get preserved.
Even with Rome, my theory checks out. We have a lot of Roman ruins because Rome was heavily depopulated after the Roman empire collapsed. A lot of buildings were probably abandoned and then buried by dirt over time (like the Roman Forum). The only other preserved ruins were buildings that were repurpose d (Agrippa's Pantheon, Colessium, aqueducts, etc).
Big difference in cities built of masonry and those built of wood. Eastern Asia had many of the largest cities through history but they were often wooden and thus much less has survived than Rome
That makes sense. Hampi and Angkor had a lot of buildings made out of stone. But what about Patna and Mathura? Ancient primary source accounts mention lots of buildings made out of stone.
Angkor Wat is not nearly as old as your Indian examples. It's similar age to Notre Dame cathedral. The main temple complex is the best preserved building in the area with some others that I think came later less well preserved. There are many many smaller temples very poorly preserved. As for a "city" of Angkor, it's now Siem Reap and there isn't much of the ancient city within the modern city.
>> My guess is that for a city to have relatively well preserved ruins, it has to be completely abandoned due to some calamity. If a city is continuously occupied, old buildings get incrementally replaced by newer buildings, and very few old buildings get preserved.
The calamity could also be economic. It is heartbreaking to see cities in industrial towns hollowed out -- from what I understand due to a major factory closure. It has been some decades for these cities, so not quite "ancient ruins" but eventually they would turn into that I imagine. However, modern wood homes are unlikely to survive the ages of course.
So in 4000 years, archeologists digging up the the Midwest will theorize that Ohio valley was the center of a vast industrial society. They will theorize that it may be linked to a settlement that was known in ancient times as the mythical city of "New York", which is referenced several times in ancient literature, of which no ruins have been found.
A colleague’s son specializes in stripping old industrial sites that are no longer in use. They move into some abandoned part of the rust belt and systematically tear out every piece of scrap metal they can find. They’ve been pretty busy. I’m sure the concrete and brick stays behind, but the in situ lifespan of useful, durable materials is much shorter than you’d think.
Take a drive in many US cities. There are many empty high-rises that are unlikely to be filled. Eventually, there's going to be a demolish or "stabilize in place" decision for lots of these places.
There's a big warehouse in the downtown of my city that's been abandoned for 30 years -- it was a refrigerated produce warehouse that had a built in train terminal. It will never be demolished unless someone with unlimited pockets like Federal government wants to build something there.
On a smaller scale, I live in Baltimore and there are whole blocks of boarded-up three-story brick row-homes, some of them with the ceilings collapsed and trees growing up through them, and big wooden buttresses in place to keep the facade from collapsing.
I grew up around here, and spent a half-decade in Colorado. It feels like such a waste seeing the densely-packed tract housing appearing in the middle of the plains there as I drive by boarded-up crumbling ruins here.
Agreed. The fate of really interesting cities like Baltimore is this weird intersection of politics, policy and economics. It seems so wasteful and needless.
I can recommend the “fall of civilizations” podcast. The common theme was some kind of pressure (ecological, geopolitical, etc.) causing a rapid decline in population.
> A lot of cities in India have been continuously occupied for over 2000 years (Kalyan, Ujjain, Bharuch, Patna). A lot of them don't have any obvious ruins from that era
A lot of ancient ruins are _under_ the city itself. e.g
Yes, in some parts of Europe it is almost impossible doing some digging for infrastructure without coming into some old structure.... usually mosaics, old villas, old graves, etc...
> It is almost impossible doing some digging for infrastructure without coming into some old structure.... usually mosaics, old villas, old graves, etc...
Or if you're _very_ unlucky, an unexploded bomb from the 1940s in a questionable state of chemical decay.
Some of the oldest cities in the world are in the Levant - Aleppo and Damascus in Syria. Or Jericho in Palestine. The trouble is that those cities also have had gone through significant conflict, so ruins tend to not survive.
It’s unclear how many of these cities survive due to the conditions of the desert vs. other areas.
The Mediterranean and Middle East are relatively dry climates which would favor stone construction. Temperate and wet climates may see more wood construction. Wood will not last long in a temperate or wet climate...
Looking at colonial New England the main ruins are stone fences separating property, nails, and grave stones along with a few preserved homes.
I’d be curious if it’s practical to tell the size of any of the population centers for pre columbian New England given how little remains of the colonial period.
There are old towns in the U.S. that are ancient ruins today, too. People go where they can make a livelihood and sometimes that means leaving town when the mine closes.
Nah.... Just look at Detroit. That's a modern version of a city in Ruin... Rome didn't get abandoned in a day. It took about 100 years, to go from 1 mill, to between 30-60k inhabitants. The most visible today's comparison would be Detroit (or parts of it).
Smaller structures just disappear, but the large ones remain and look like relics:
Also, many cities do have old antique buildings in them (coliseums, or amphitheaters), and mediterranean europe is dotted with them. From Spain to Italy to Greece and Albania. That doesn't mean that the people left from the cities. It just meant that they stopped having a purpose due to economic shortages, and just went to decay into old crumbling buildings that are just there for the locals.
Very similar to old ware houses, or abandoned train stations, or stadiums, in industrial cities.
Some Detroit skyscrapers sat abandoned for 50-60 years with no heat or electricity. Sure some were falling apart and became a hazard with chunks of brick or concrete hitting the unwary pedestrian but the majority held up fairly well.
When the billionaire Dan Gilbert bought them to rehabilitate he few major structural problems. So I think if major cities are abandoned their skyline may look somewhat familiar centuries from now.
I was big proponent for mass timber until engineer told me the lifespan might be poor due to adhesives in fabrication. Can't find any solid analysis though.
77 comments
[ 3.8 ms ] story [ 138 ms ] threadhttps://en.wikipedia.org/wiki/Ingalls_Building
Maintaining concrete is a matter of having routine structural inspectors come out to poke and prod the concrete. Worn traffic areas get patches and sealants. Areas with a lot of runoff get seals to direct water in ideal ways. Etc.
0. https://www.sika.com/en/construction/structural-strengthenin...
1. https://youtu.be/c0Pj5Qdy9IU
A farm near where I grew up had a big barn, built in the 1700s that was in daily use until the mid 80s. Due to a family/inheritance dispute, maintenance ceased in the 90s. At some point, the roof leaked and that set in motion things that resulted in collapse last year.
https://en.wikipedia.org/wiki/Reinforced_concrete_structures...
https://www.fastcompany.com/3037370/concrete-is-not-as-stron...
Most concrete structures with long design lifetimes made of concrete (some dams, levees, bridges - but not all by any stretch) will use design techniques to minimize or remove the use of rebar, such as compression only designs , or ‘overbuilding’ so expected corrosion still leaves the structure strong enough over it’s design life.
Generally, concrete is a strongly base compound and protects rebar from corrosion. Over time however it can be influenced by the environment, with those base compounds reacting and leaving a less protective environment. Some environments do it faster than others.
If the covering concrete is strong enough/thick enough, the pressure caused by the rebar turning to rust inside the concrete won’t crack it - if the rebar was structurally important (pretty much always or why use it?) it still weakens the structure though, sometimes dangerously.
Attempts to mitigate the risk where weatherproofing is not an option and rebar is essential for structural reasons like concrete roadways and bridges have had their share of disasters. epoxy coated rebar for instance can lead to unpredictable and sometimes rapid failures in exactly the types of environments it was expected to help in [https://www.fhwa.dot.gov/publications/publicroads/99novdec/r...]
https://partridge.com.au/concrete-cancer-what-is-it-and-what...
Some other failure modes include the Alkali-Silica reaction (sometimes confusingly named concrete cancer too, though fundamentally different) [https://en.m.wikipedia.org/wiki/Alkali–silica_reaction]
The more dependent a design is on an element that can corrode, and the tighter it’s design tolerances, the more fragile it is. The more overbuilt it is, and more conservative the design, the more expensive it is.
Taking a low margin design and then not maintaining it is a recipe for this kind of disaster [https://www.google.com/amp/s/www.independent.co.uk/news/worl...] and lots of dead people.
https://www.tracesofwar.com/sights/12168/German-Coastal-Batt...
This condition can be detected and fixed before failure.
Buildings only last 50 years or so before being torn down and rebuilt.
https://www.mynicehome.gov.sg/article/dealing-with-spalling-...
Anyway, the sequence is that micro cracks form on the concrete and expose the steel, then the exposed steel rusts and pushes more concrete away, exposing more steel. This too can be fixed before it becomes a problem.
People on this thread claiming a collapse in 60 years are probably not civil engineers. People claiming that reinforced structures will outlast the Pyramids at Giza are definitely not civil engineers.
What I don't agree is on the classification of that as a "fatal flaw". Looks like we are in serious disagreement on the goal of our constructions.
It's not a fatal flaw in terms of building a perfectly serviceable structure.
It's a fatal flaw in terms of building a structure that lasts the ages like the pyramids.
Like all engineering problems, the solution is greatly dependent on your goals.
Over time however, carbon dioxide from the atmosphere slowly seeps into the concrete (anything that's only intermittently wet fares the worst here), turning the calcium hydroxide into calcium carbonate. While this has the beneficial side effect of actually increasing the strength of the concrete itself, it also lowers its pH value, which means the rebar is no longer protected against corrosion once the carbonation process reaches the rebar.
In some places - Detroit is an example - people start leaving, the tax base dwindles, and by the time they realize the need to demolish things, the funds aren't there. In some cases, the city pulls in its borders and declares the former-city areas someone else's problem.
Here's a Detroit residential neighborhood suffering it now: https://www.msn.com/en-us/news/us/eerie-images-of-detroits-m...
I don't think that's a totally unfair statement depending on the region though. At least in Seattle a fair amount of homes are Craftsman homes which haven't aged well since they were ordered directly from a Sears catalog without considering the very wet local climate of the Northwest. (And yes, that Sears and that Craftsman.)
I'm aware of Sears catalog homes but not of any link between the Sears owned Craftsman tool brand and the craftsman style of home, which is connected to the Arts and Crafts design movement. Can you provide a reference?
I do wonder if the tool name (apparently a brand purchased from a small Chicago toolmaker by Sears in 1927) was inspired in part by the architectural movement, which was the product of a specific designer (Gustav Stickley) in the early 1900s.
I couldn't find any references to such a connection though.
The Cathedrals stand because they have been maintained by each generation -- and each generation has added something: a chapel, a statue, a ceiling boss. To this day you will often find them surrounded by scaffolding. It detracts from the view but it's as much a part of the process as the stone.
Angkor Wat is no older, yet it has crumbled. Its maintenance ceased for generations. The difference is stark.
(Angkor is now seeing something of a revival. Restoration work has occurred over the last two or three generations, and more will happen now as the Khmer people become wealthier again.)
These buildings are a reminder that there are long-term dynamics of birth and death and reproduction that outlive the individual.
Why do you have to make this about something being wrong with a group of people?
If they don't have the dynamism, economy, or youth of other countries, they fixate on what they do have — buildings which are faded memories of the cultures which built them.
But for honesty's sake, I will note here that, originally, I ended the parent post:
> Maybe the absence of these reminders is one of the things that's wrong with North Americans.
I do think there's a problem to do with being historically adrift, but I won't belabor it here.
My guess is that for a city to have relatively well preserved ruins, it has to be completely abandoned due to some calamity. If a city is continuously occupied, old buildings get incrementally replaced by newer buildings, and very few old buildings get preserved.
Even with Rome, my theory checks out. We have a lot of Roman ruins because Rome was heavily depopulated after the Roman empire collapsed. A lot of buildings were probably abandoned and then buried by dirt over time (like the Roman Forum). The only other preserved ruins were buildings that were repurpose d (Agrippa's Pantheon, Colessium, aqueducts, etc).
The calamity could also be economic. It is heartbreaking to see cities in industrial towns hollowed out -- from what I understand due to a major factory closure. It has been some decades for these cities, so not quite "ancient ruins" but eventually they would turn into that I imagine. However, modern wood homes are unlikely to survive the ages of course.
There's a big warehouse in the downtown of my city that's been abandoned for 30 years -- it was a refrigerated produce warehouse that had a built in train terminal. It will never be demolished unless someone with unlimited pockets like Federal government wants to build something there.
I grew up around here, and spent a half-decade in Colorado. It feels like such a waste seeing the densely-packed tract housing appearing in the middle of the plains there as I drive by boarded-up crumbling ruins here.
A lot of ancient ruins are _under_ the city itself. e.g
Rome: https://en.wikipedia.org/wiki/Monte_Testaccio
Italy: https://www.bbc.co.uk/news/world-europe-52818746
It's sometimes theorised that the ground level in cities rises over the centuries, due to sheer accumulation of material. https://www.quora.com/Why-over-the-centuries-cities-such-as-...
https://www.quora.com/Why-is-the-ground-level-of-Ancient-Rom...
Because people build over the ruins and rubble; and put a new layer of surfacing on the roads periodically.
http://www.bbc.com/travel/story/20191007-mexico-citys-secret...
Or if you're _very_ unlucky, an unexploded bomb from the 1940s in a questionable state of chemical decay.
https://www.huffingtonpost.co.uk/2012/03/15/london-2012-olym...
https://www.dw.com/en/500-kilogram-wwii-bomb-sparks-evacuati...
https://www.bbc.co.uk/news/uk-england-london-43027472
https://www.bbc.co.uk/news/av/world-europe-24799937
Some of the oldest cities in the world are in the Levant - Aleppo and Damascus in Syria. Or Jericho in Palestine. The trouble is that those cities also have had gone through significant conflict, so ruins tend to not survive.
The Mediterranean and Middle East are relatively dry climates which would favor stone construction. Temperate and wet climates may see more wood construction. Wood will not last long in a temperate or wet climate...
Looking at colonial New England the main ruins are stone fences separating property, nails, and grave stones along with a few preserved homes.
I’d be curious if it’s practical to tell the size of any of the population centers for pre columbian New England given how little remains of the colonial period.
Detroit's old station: https://media.wired.com/photos/5b28344e11196626aaeb16c4/mast...
Ford buys Detroit's deserted, century-old train station
https://www.cbsnews.com/news/ford-buys-michigan-central-depo...
Also, many cities do have old antique buildings in them (coliseums, or amphitheaters), and mediterranean europe is dotted with them. From Spain to Italy to Greece and Albania. That doesn't mean that the people left from the cities. It just meant that they stopped having a purpose due to economic shortages, and just went to decay into old crumbling buildings that are just there for the locals.
Very similar to old ware houses, or abandoned train stations, or stadiums, in industrial cities.
Plenty of other ruins in the US: https://www.bbc.com/culture/article/20141208-amazing-photos-...
When the billionaire Dan Gilbert bought them to rehabilitate he few major structural problems. So I think if major cities are abandoned their skyline may look somewhat familiar centuries from now.