The problem with reinforced concrete (2016)(theconversation.com)
theconversation.com
The problem with reinforced concrete (2016)
https://theconversation.com/the-problem-with-reinforced-concrete-56078
191 comments
> The cheapest bidder will generally win and their building will last the "design life" of the building, but often not much more. The simplest way to change this is to extend the design life, which would result in stainless steels or another more expensive material being used in this application.
Just FYI, on a ‘plan and spec’ construction project, all material is specified by the architect and engineers. If the project specs say you have to use stainless steel rebar, then even the low bidder will have it included.
Just FYI, on a ‘plan and spec’ construction project, all material is specified by the architect and engineers. If the project specs say you have to use stainless steel rebar, then even the low bidder will have it included.
But on big projects, doesn't the architect often work for the bidder?
No, the architect works for the building owner (or tenant). The bidder is typically a general contractor.
but... there is also bidding for selecting architects, is there not?
I think that comment was asking about "Design-Build" projects which are becoming more and more common.
I'm not in traditional engineering but I always felt like "specs" only tell part of the story. In your example they may use stainless steel but cut corners by using less of it than they really should or maybe just use really cheap stainless steel which leads to other problems.
I've noticed manufacturing companies like big auto will try to solve for this by creating more specs for parts provided by suppliers but that's a losing battle as its always a race to the bottom. Plus now you need large testing teams to verify parts meet all these different specs. Maybe some percentage of the parts do - what do you in that case? The whole process can be a mess.
I've noticed manufacturing companies like big auto will try to solve for this by creating more specs for parts provided by suppliers but that's a losing battle as its always a race to the bottom. Plus now you need large testing teams to verify parts meet all these different specs. Maybe some percentage of the parts do - what do you in that case? The whole process can be a mess.
You bring up some good points.
Construction specs often include “Allowed manufacturers” to limit your choices to certain vendors, which theoretically means you get quality material. For stainless steel, sometimes they’ll specify which alloy you need to use (304L and 316L are the most common) You certainly could submit the specified manufacturer’s product and then switch it out for a cheaper option, but if you’re caught, you could be forced to correct the work with the right material or be financially on the hook for another contractor performing the work. It would be up to someone else to notice that the steel contractor isn’t using the specified material, which may never happen.
The ‘use less of it than needed’ problem would ideally be caught by an inspector, but they certainly aren’t perfect.
Here’s a link to Cleveland Clinic’s electrical spec, if you’re curious how detailed they get: http://portals.clevelandclinic.org/Portals/57/2012_Elec%20Sp...
Construction specs often include “Allowed manufacturers” to limit your choices to certain vendors, which theoretically means you get quality material. For stainless steel, sometimes they’ll specify which alloy you need to use (304L and 316L are the most common) You certainly could submit the specified manufacturer’s product and then switch it out for a cheaper option, but if you’re caught, you could be forced to correct the work with the right material or be financially on the hook for another contractor performing the work. It would be up to someone else to notice that the steel contractor isn’t using the specified material, which may never happen.
The ‘use less of it than needed’ problem would ideally be caught by an inspector, but they certainly aren’t perfect.
Here’s a link to Cleveland Clinic’s electrical spec, if you’re curious how detailed they get: http://portals.clevelandclinic.org/Portals/57/2012_Elec%20Sp...
Wasn't one of the problems with Boston's Big Dig that the contractors put an extra inch between bolts which saved them a ton of money (but ultimately killed a person)?
Most manufacturing specs in US industries such as aerospace and defense are extremely well defined. They don't usually leave enough meat to cut corners in significant areas. They are typically fairly robust in that they are self-assuring. When specs are written correctly they are extremely difficult to subvert in one area and still come up with anything that could be confused with a conforming product. Plus the penalties for actively subverting these specs can be quite severe.
That said, I can almost guarantee the specs for automotive manufacturers are less strict and the penalties less severe simply because the specs are made to be cost-centric rather than performance-centric.
That said, I can almost guarantee the specs for automotive manufacturers are less strict and the penalties less severe simply because the specs are made to be cost-centric rather than performance-centric.
Is it a good thing for society to directly incentivize the construction of longer lasting buildings?
IMO yes; if the materials cost a lot of time/carbon/resources to produce, then we should make them last!
I agree. Its like one of the few things we can give future generations. 'sorry about the debt, but heres some buildings'
You're implicitly assuming they'll want those buildings, and I'm not sure they will. Perhaps those buildings will be unsuitable for their activities, or the buildings will be found unsafe for some unforeseen reason. If either of these possibilities occur, the additional time, energy, and pollution you incurred to make the buildings rust-resistant are waste.
No, time is not an externality: maybe time under construction yields to disruption to neighbours under construction and we can charge for that. Resources are fully internalized. If a building needs x sand and another needs 2x sand, the second will pay twice for sand. Carbon is externalized, but that's a general problem. How do we know that making a lasting building is better/worse than having the building not exist / exist and having people driver farther / closer?
Simple, for externalities, you directly charge for the externality.
All these stop-gap "it costs carbon, so we must make it last 50 years" is like placing massive `if-then-else` statements throughout your codebase and then being surprised when the emergent behaviour of your program somehow results in uglier, more carbon polluting, sicker buildings that are now 100 years old and imposing massive costs on society around them.
Simple, for externalities, you directly charge for the externality.
All these stop-gap "it costs carbon, so we must make it last 50 years" is like placing massive `if-then-else` statements throughout your codebase and then being surprised when the emergent behaviour of your program somehow results in uglier, more carbon polluting, sicker buildings that are now 100 years old and imposing massive costs on society around them.
Japan builds buildings to last 30 years on average. They tear them down and build new ones. Is it good, bad, something else? I don’t know, except not everyone builds for things to last a long time.
People quote this figure often, but it really only applies to detached single-family dwellings, which are commonly built for a single owner. Japan certainly doesn't build larger structures such as office buildings for thirty-year lifespans – no one has floated any plans to tear down the Kasumigaseki Building yet: https://en.wikipedia.org/wiki/Kasumigaseki_Building
Have things changed in the last decade or so[1]?
Japanese loathe “second hand” stuff if they can avoid it. This includes property. The service life for buildings is 47 to 50 years or so, for depreciation purposes.
Totally unrelated, but I love that 1000 year old wooden temples get rebuilt every 20 years or so[2] because of the religious idea of renewal.
[1] https://japanpropertycentral.com/2012/06/what-is-the-lifespa...
[2]https://chrispythoughts.wordpress.com/2012/10/19/558/
Japanese loathe “second hand” stuff if they can avoid it. This includes property. The service life for buildings is 47 to 50 years or so, for depreciation purposes.
Totally unrelated, but I love that 1000 year old wooden temples get rebuilt every 20 years or so[2] because of the religious idea of renewal.
[1] https://japanpropertycentral.com/2012/06/what-is-the-lifespa...
[2]https://chrispythoughts.wordpress.com/2012/10/19/558/
> The service life for buildings is 47 to 50 years or so, for depreciation purposes.
That doesn't tell you much: in the US the lifetime of a residential rental building is 27.5 years for depreciation purposes, and 39 for non-residential: https://www.irs.gov/publications/p946
That doesn't tell you much: in the US the lifetime of a residential rental building is 27.5 years for depreciation purposes, and 39 for non-residential: https://www.irs.gov/publications/p946
Possibly.
"A recent innovation in the Japanese real estate industry to promote home ownership is the creation of a 100-year mortgage term. The home, encumbered by the mortgage, becomes an ancestral property and is passed on from grandparent to grandchild in a multigenerational fashion. We analyze the implications of this innovative practice, contrast it with the conventional 30-year mortgage popular in Western nations and explore its unique benefits and limitations within the Japanese economic and cultural framework." The 100-year Japanese residential mortgage: An examination (1995) (https://www.sciencedirect.com/science/article/abs/pii/106195....)
"A recent innovation in the Japanese real estate industry to promote home ownership is the creation of a 100-year mortgage term. The home, encumbered by the mortgage, becomes an ancestral property and is passed on from grandparent to grandchild in a multigenerational fashion. We analyze the implications of this innovative practice, contrast it with the conventional 30-year mortgage popular in Western nations and explore its unique benefits and limitations within the Japanese economic and cultural framework." The 100-year Japanese residential mortgage: An examination (1995) (https://www.sciencedirect.com/science/article/abs/pii/106195....)
My understanding is the cost is mostly the land and the building not so much. I think Sweden introduced a law limiting mortgages to ~100 years[1] because property prices were becoming unaffordable to many. So this may be more about "affordability" than longevity of buildings, but time will tell.
[1]https://www.thelocal.se/20160324/sweden-limits-mortgage-loan...
[1]https://www.thelocal.se/20160324/sweden-limits-mortgage-loan...
One historic building being 50 years old proves very little - of course some buildings last longer than the average. E.g. every one of the famous Dojunkai apartment buildings has been demolished.
Maybe sufficient to require that construction put down enough money to cover deconstruction and cleanup when building.
Yeah I think this is a better way to put it. By incentivising long-lasting buildings you are better pricing in the amortised (environmental) negative externalities of tearing down and rebuilding.
I see two arguments against:
1. Future buildings will be so much better for the environment that increasing costs today for long lasting buildings or having to wait longer for environmentally better buildings is a net negative
2. Old buildings are typically not useful and so we shouldn’t encourage a future full of them (examples: smaller houses in city centres function ok but aren’t well insulated and could reduce total environmental costs of the city if they were replaced with more dense accommodation; many old churches see little use; many old buildings or rooms of them are no longer fit for any efficient purpose and so are wasting resources, eg banks with lots of space for tellers/vaults/deposit boxes or stock exchanges with big trading pits or warehouses which cannot be converted or even the rooms above shops which often seem to be disused. I have also seen other places where good use is still made of old buildings (typically long lived institutions like schools or societies or universities) though perhaps not as efficient use as might be possible. Obviously there are other cultural arguments for keeping old buildings around (but sometimes I worry regulations enforcing this can be too prohibitive, eg freezing an old building that has been changing slowly over many years at the point it becomes protected).
I see two arguments against:
1. Future buildings will be so much better for the environment that increasing costs today for long lasting buildings or having to wait longer for environmentally better buildings is a net negative
2. Old buildings are typically not useful and so we shouldn’t encourage a future full of them (examples: smaller houses in city centres function ok but aren’t well insulated and could reduce total environmental costs of the city if they were replaced with more dense accommodation; many old churches see little use; many old buildings or rooms of them are no longer fit for any efficient purpose and so are wasting resources, eg banks with lots of space for tellers/vaults/deposit boxes or stock exchanges with big trading pits or warehouses which cannot be converted or even the rooms above shops which often seem to be disused. I have also seen other places where good use is still made of old buildings (typically long lived institutions like schools or societies or universities) though perhaps not as efficient use as might be possible. Obviously there are other cultural arguments for keeping old buildings around (but sometimes I worry regulations enforcing this can be too prohibitive, eg freezing an old building that has been changing slowly over many years at the point it becomes protected).
> Old buildings are typically not useful.
My 95 year old brick house would beg to differ on utility of old buildings. My prior house was over 230 years old and provided 14 years of excellent utility to me.
My 95 year old brick house would beg to differ on utility of old buildings. My prior house was over 230 years old and provided 14 years of excellent utility to me.
Old is certainly relative. A 200 year old house fits more into point 1 than 2 above. A 230 year old office block tends to not be such a well suited building.
Good point.
What hubris for a landowner to assume there will be a need for a building 1000 years hence.
Buildings aren’t usually demolished and replaced because they are dilapidated; rather, it’s because the new owner has a different need (and a different aesthetic.)
A building that takes 1000 to crumble is just as a much a blight — maybe more — as a plastic bottle that takes 10,000 years to crumble.
What hubris for a landowner to assume there will be a need for a building 1000 years hence.
Buildings aren’t usually demolished and replaced because they are dilapidated; rather, it’s because the new owner has a different need (and a different aesthetic.)
A building that takes 1000 to crumble is just as a much a blight — maybe more — as a plastic bottle that takes 10,000 years to crumble.
Arguably for many buildings we should be going the other way - if the average house is remodeled or torn down in 30-40 years perhaps we should be building out of renewable materials that are designed to last long and no more (think hay bales covered with mud).
Why do we not make clothing that can last 1000 years, be passed down, etc.?
I contend that buildings, with a few exceptions, are consumables. Whether wise or not, humans like to build new things, customizable to their own tastes.
An office building that lasts ‘only’ 50 years instead of 500 shouldn’t be surprising. In 50 years time, for most buildings, even if it could last another few decades, it will be torn down and replaced. That’s just what humans do. States differently, even if everyone at the time knew concrete/rebar would only last 50 years and not the 1000+ years, it wouldn’t have made a difference, for nobody — short of a Pharaoh — has any interest in such a permanent structure. Cities come and go, buildings come and go, rivers and shorelines change, etc. it’s not reasonable to assume the desirable center of activity (either residential or commercial) in which one builds will even be there 50 years hence. So why worry about how long the building will last?
I contend that buildings, with a few exceptions, are consumables. Whether wise or not, humans like to build new things, customizable to their own tastes.
An office building that lasts ‘only’ 50 years instead of 500 shouldn’t be surprising. In 50 years time, for most buildings, even if it could last another few decades, it will be torn down and replaced. That’s just what humans do. States differently, even if everyone at the time knew concrete/rebar would only last 50 years and not the 1000+ years, it wouldn’t have made a difference, for nobody — short of a Pharaoh — has any interest in such a permanent structure. Cities come and go, buildings come and go, rivers and shorelines change, etc. it’s not reasonable to assume the desirable center of activity (either residential or commercial) in which one builds will even be there 50 years hence. So why worry about how long the building will last?
The nice thing about buildings which last a long time is, the good ones can be kept around. It's the good side of survivorship bias.
One reason to prefer shorter-lasting buildings is to encourage higher density over time.
How can I know if a building was designed to last a long time? Is it the materials, the method of construction?
Yes.
Please elaborate. Which materials and methods?
There is no way to know other than to ask the architect. You can make educated guesses but that still won't tell you. Even then it's up to the contractors to have done everything properly.
Or if it's made of stone. Stacking giant stones on top of each other is a sure-fire way to make a building outlive you.
After that, the longest-lived buildings that I am aware of are made of wood. The catch is they've been rebuilt 50 times, once per time they burned to the ground.
After those, the longest-lived buildings are made of Roman concrete that we can't reproduce. (To give you an idea how insane Roman concrete was, you can go kayaking north of Naples, and kayak through a concrete Roman building that is sitting on piles in the Mediterranean sea)
Or if it's made of stone. Stacking giant stones on top of each other is a sure-fire way to make a building outlive you.
After that, the longest-lived buildings that I am aware of are made of wood. The catch is they've been rebuilt 50 times, once per time they burned to the ground.
After those, the longest-lived buildings are made of Roman concrete that we can't reproduce. (To give you an idea how insane Roman concrete was, you can go kayaking north of Naples, and kayak through a concrete Roman building that is sitting on piles in the Mediterranean sea)
> Roman concrete that we can't reproduce.
That claim seems to date to a particular article written in 2017 that wasn't well sourced. Roman concrete is interesting stuff and has useful properties, but humans have since created concrete mixtures that are far superior. But they're expensive, so it's not too surprising we don't see them getting used in buildings that compare less than favorably to a temple built a couple thousand years ago. Survivorship bias taken to the extreme.
That claim seems to date to a particular article written in 2017 that wasn't well sourced. Roman concrete is interesting stuff and has useful properties, but humans have since created concrete mixtures that are far superior. But they're expensive, so it's not too surprising we don't see them getting used in buildings that compare less than favorably to a temple built a couple thousand years ago. Survivorship bias taken to the extreme.
I asked my dad about this a while back - he spent his entire career in civil engineering and he said almost exactly what you just did.
Basically; modern concrete is far better, but often not built that way.
I haven't seen that theory tested. I can't find any tests or studies anywhere of replicated Roman concrete. And no tests of genuine Roman concrete, either. We don't know how it actually performs. So to make a comparison to modern concrete is specious.
Modern concretes can do a whole lot of stuff Roman concrete can't, because there are so many formulations of it. But if you want to stick a building literally in the ocean and have it never ever disappear, nobody has shown that we can actually do it today.
There's a whole lot of theory and talk by experts, about how we don't need to make it, but if we wanted to, boy would it be easy, but don't worry, modern concrete is just so amazing, you should just use that, for modern use cases, and oh by the way, it would be too expensive to make, even though we haven't actually made it or tried to bring the price down.
There's a world of practical experience needed to claim for a fact that modern concrete is legitimately better, much less that we can actually make it and that it would hold up as we expect. I'm still waiting for concrete evidence.
Modern concretes can do a whole lot of stuff Roman concrete can't, because there are so many formulations of it. But if you want to stick a building literally in the ocean and have it never ever disappear, nobody has shown that we can actually do it today.
There's a whole lot of theory and talk by experts, about how we don't need to make it, but if we wanted to, boy would it be easy, but don't worry, modern concrete is just so amazing, you should just use that, for modern use cases, and oh by the way, it would be too expensive to make, even though we haven't actually made it or tried to bring the price down.
There's a world of practical experience needed to claim for a fact that modern concrete is legitimately better, much less that we can actually make it and that it would hold up as we expect. I'm still waiting for concrete evidence.
Didn't they figure out that Roman concrete was made or infused with ash from a volcano or something?
https://en.wikipedia.org/wiki/Roman_concrete
https://en.wikipedia.org/wiki/Roman_concrete
Yes, but it is not that we don't use (or at least it is possible to use) ashes in "modern" concrete, typically we use ashes that are a by-product of (carbon based, yes I know) electrical generation plants.
The bigger difference in components is the kind of cement the Romans (and we "moderns" until a few years ago) used, i.e. pozzolanic cement, nowadays everything is "portland" cement.
BUT the definite difference is the kind of structures, Romans did not use "reinforced" concrete, only various types of "plain, non-reinforced" concrete, and all their structures are based on the main characteristic of concrete, which is its resistance to compression.
The idea of reinforced concrete is all about adding to a material with excellent compression resistance (but no resistance on tension/traction) a material (steel) with excellent resistance to tension/traction and relatively poor (in the quantities used in reinforced concrete) resistance to compression, obtainining a composite material that excels in both.
About ashes, overall it is more about their size that about their nature, concrete is a composite and if you have all possible sizes of aggregates (ashes are very, very small sized particles) in the "right" amount you essentially fit "better" the space, i.e. you have a higher density of the resulting composite, and, particularly when compression resistance is the goal, the higher the density the better the resistance.
Imagine (say) that you have to fill a 100x100x100 mm box with 10 mm balls, you can fit in them a certain amount of these balls (roughly 10x10x10=1000), but you are leaving lots of "air" between them, a single 10 mm ball is 2/3x3.1416x5^3=262 mm3, so the 1000 balls total 262,000, but the volume of the box is 100x100x100= 1,000,000, now if you have some 2 mm balls you can add them in the same volume, and then if you have some 0.5 mm balls you can put some of them in that same box as well, etc.
The bigger difference in components is the kind of cement the Romans (and we "moderns" until a few years ago) used, i.e. pozzolanic cement, nowadays everything is "portland" cement.
BUT the definite difference is the kind of structures, Romans did not use "reinforced" concrete, only various types of "plain, non-reinforced" concrete, and all their structures are based on the main characteristic of concrete, which is its resistance to compression.
The idea of reinforced concrete is all about adding to a material with excellent compression resistance (but no resistance on tension/traction) a material (steel) with excellent resistance to tension/traction and relatively poor (in the quantities used in reinforced concrete) resistance to compression, obtainining a composite material that excels in both.
About ashes, overall it is more about their size that about their nature, concrete is a composite and if you have all possible sizes of aggregates (ashes are very, very small sized particles) in the "right" amount you essentially fit "better" the space, i.e. you have a higher density of the resulting composite, and, particularly when compression resistance is the goal, the higher the density the better the resistance.
Imagine (say) that you have to fill a 100x100x100 mm box with 10 mm balls, you can fit in them a certain amount of these balls (roughly 10x10x10=1000), but you are leaving lots of "air" between them, a single 10 mm ball is 2/3x3.1416x5^3=262 mm3, so the 1000 balls total 262,000, but the volume of the box is 100x100x100= 1,000,000, now if you have some 2 mm balls you can add them in the same volume, and then if you have some 0.5 mm balls you can put some of them in that same box as well, etc.
I'm going way out on a limb here, and claim both.
There is an interplay between the two. Wood, for example in a dark and dry place, can last for a very long time, but I doubt there are many wooden structures that are, say 2000 years old. Perhaps some supports for tunnels in dry climates. Those organic compounds will break down over time. The method of using the wood, how it's protected from its environment is important.
Stone is another obvious example. Plenty of stone buildings have been built and crumbled, but the really well cut, fit, and stacked stones seem to last a long time. There are countless temples and castles that are simple stone with very tight tolerances (methods) that last a long time. The pyramids are a spectacular example.
Hoover Dam is reinforced concrete, and is expected to last a long time. I suspect the steel will rust away, but the compression from the water will keep the concrete stable. (not a civil engineer, but I'd bet this was seriously thought about by civil engineers when it was built)
The materials are important, but they can be misused, and master craftsmen can use them far better than I ever will, So the methods matter as well.
_edit_
I looked it up, hoover dam used steel pipes, not solid bars, so there's room for the corrosion to expand into the void created by the pipes.
Master craftsmen I tell ya, they think hard about that kind of stuff.
The materials are important, but they can be misused, and master craftsmen can use them far better than I ever will, So the methods matter as well.
_edit_
I looked it up, hoover dam used steel pipes, not solid bars, so there's room for the corrosion to expand into the void created by the pipes.
Master craftsmen I tell ya, they think hard about that kind of stuff.
One way is to see how the building protects itself from water. Water is the great destroyer of buildings.
A flat roof, for example, is very prone to leaking, which when not constantly taken care of will wreck the building. Another is if the roof keeps water off of the walls (how big the overhang is). Many buildings have eaves that are an inch or two. The exterior walls of these buildings won't last.
Any building on a flat area near a river is going to flood. Any building without proper drainage around it is going to rot away.
Wood shingles need constant maintenance or goodbye to the building.
A flat roof, for example, is very prone to leaking, which when not constantly taken care of will wreck the building. Another is if the roof keeps water off of the walls (how big the overhang is). Many buildings have eaves that are an inch or two. The exterior walls of these buildings won't last.
Any building on a flat area near a river is going to flood. Any building without proper drainage around it is going to rot away.
Wood shingles need constant maintenance or goodbye to the building.
> Many buildings have eaves that are an inch or two. The exterior walls of these buildings won't last.
Unless you’re talking about a very old house, this depends a lot on the local climate, construction materials, and design.
You can pretty successfully mitigate water entry with a dimple membrane and a gutter on an exposed wall, for example, and obviously this is a minimal concern if your house is in a desert.
(I’m not a trained architect, just someone interested in building science.)
Unless you’re talking about a very old house, this depends a lot on the local climate, construction materials, and design.
You can pretty successfully mitigate water entry with a dimple membrane and a gutter on an exposed wall, for example, and obviously this is a minimal concern if your house is in a desert.
(I’m not a trained architect, just someone interested in building science.)
I live in Rain City (Seattle). Quite a lot of homes are built with ridiculously tiny eaves. I'd never buy one of those.
My house has eaves that stick out about 2 feet. It added nothing significant to the cost, but boy what a difference it makes. The exterior walls almost never get wet. The windows and their frames stay dry and free of rot. No mildew. Haven't even needed to repaint.
There are a lot of things one can do with a house that, at trivial expense, will dramatically improve its life and lower maintenance costs.
Here's another one. Run the plumbing up interior walls. Then it won't freeze.
My house has eaves that stick out about 2 feet. It added nothing significant to the cost, but boy what a difference it makes. The exterior walls almost never get wet. The windows and their frames stay dry and free of rot. No mildew. Haven't even needed to repaint.
There are a lot of things one can do with a house that, at trivial expense, will dramatically improve its life and lower maintenance costs.
Here's another one. Run the plumbing up interior walls. Then it won't freeze.
There's nothing wrong with having long eaves if that's your preference; I'm just pointing out that there are a lot of factors that go in to building a long-lasting structure, and the answer to most questions around best practices is "it depends."
If you have a two-storey house in a wet area that gets a lot of storm activity coming from the northeast, for example, and you have an exposed northeast-facing wall, the eaves aren't going to do much to shield that wall from driving rain. You'd have to make sure it's dealt with in other ways.
> Here's another one. Run the plumbing up interior walls. Then it won't freeze.
Same with this - it might be good advice in Seattle, but if I told a local builder to worry about frost mitigation where I live now (Singapore) they'd probably question my sanity.
If you have a two-storey house in a wet area that gets a lot of storm activity coming from the northeast, for example, and you have an exposed northeast-facing wall, the eaves aren't going to do much to shield that wall from driving rain. You'd have to make sure it's dealt with in other ways.
> Here's another one. Run the plumbing up interior walls. Then it won't freeze.
Same with this - it might be good advice in Seattle, but if I told a local builder to worry about frost mitigation where I live now (Singapore) they'd probably question my sanity.
> might be good advice in Seattle, but if I told a local builder to worry about frost mitigation where I live now (Singapore) they'd probably question my sanity
Texas felt the same way until February!
Texas felt the same way until February!
Singapore sits basically on the equator and the lowest recorded temperature ever was 66F, so if we somehow make it below freezing then something catastrophic has happened to the earth and plumbing would be the least of our problems.
> Texas felt the same way until February!
And I have a friend who lives in Texas. The pipes in the outer walls froze and burst, the ones in the inner walls did not.
And I have a friend who lives in Texas. The pipes in the outer walls froze and burst, the ones in the inner walls did not.
> it might be good advice in Seattle
Jeez, of course one pays attention to the local climate. I don't worry about tornadoes in Seattle, but would if in the midwest.
Jeez, of course one pays attention to the local climate. I don't worry about tornadoes in Seattle, but would if in the midwest.
> Jeez, of course one pays attention to the local climate.
Believe it or not, this kind of thing isn't just immediately obvious to everyone.
Believe it or not, this kind of thing isn't just immediately obvious to everyone.
> The author states that "one of iron’s unalterable properties is that it rusts" yet further on acknowledges the existence of stainless
Even stainless steel rusts, just more slowly. Roughly 10-100x more slowly, judging by https://www.nrc.gov/docs/ML1124/ML112490377.pdf and https://www.mdpi.com/2076-3417/10/23/8705/pdf.
Even stainless steel rusts, just more slowly. Roughly 10-100x more slowly, judging by https://www.nrc.gov/docs/ML1124/ML112490377.pdf and https://www.mdpi.com/2076-3417/10/23/8705/pdf.
That doesn't smell right. I've got 15 year old knives that have never once shown signs of rust. A pair of old scissors left in the rain rusted in under a day. That puts the factor to closer to >10000 than 10 or 100...
You leave your knives outside?
Knives tend to get washed.
And immediately dried.
My knives started showing some rust spots. I thought there must be something wrong with the knives, but I realized after googling, it was something wrong with how I was washing the knifes... I left it in a tub of very hot water and soap for a day, did this multiple times, viola, rust spots.
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There are different grades of stainless steels. The common, "construction" grade stainless steels usually rust albeit very slowly. And while some of them are basically impervious to corrosion, they are usually way more expensive or have a lot less tensile strength. I don't know about knives specifically but it wouldn't surprise me if those more corrosion resistant grades are what's used to make them.
All correct. Stainless steel is 'created' by adding chrome and a few other materials depending on the desired properties. But despite that it will still rust.
I think a good analogy world be eating healthy, you'll probably live longer then soon-to-be who doesn't eat healthy but in the end both will die and seize to exist.
Material science is incredibly interesting field and I think it will play a huge role in the future. It already does.
I think a good analogy world be eating healthy, you'll probably live longer then soon-to-be who doesn't eat healthy but in the end both will die and seize to exist.
Material science is incredibly interesting field and I think it will play a huge role in the future. It already does.
Word tip: “cease to exist” rather than “seize”
Now that you said it, it totally makes sense, because too seize, means to take away as in: The police seized my laptop. Thanks ^^
Example: The Gateway Arch was surfaced with a stainless steel alloy, and it is suffering some corrosion problems today.
There are different grades of steel, doped with all sorts of additives, depending on the desired traits. The most corrosion-resistant variant today used in knives would be one of the nitrogen steels, like Nitro-V.
https://knifesteelnerds.com/2019/09/23/nitro-v-its-propertie...
But they all corrode, eventually. If you want a true corrosion-resistant metal that stays (kinda) sharp, look at one of the cobalt alloys like Stellite.
https://knifesteelnerds.com/2019/09/23/nitro-v-its-propertie...
But they all corrode, eventually. If you want a true corrosion-resistant metal that stays (kinda) sharp, look at one of the cobalt alloys like Stellite.
You may like SPY27 if cobalt is what you seek. (=> new steel which just dropped <small_value> weeks ago.)
/Acey
/Acey
What are car mufflers made of that they resist rust so well?
I'm not sure if you are being sarcastic but mufflers rust quite a bit.
plain steel, I believe, but they get very hot on trips of even a few km, which drives off any resting moisture and prevents exhaust moisture from condensing for a while after the engine is stopped.
cars that make many short trips, which never give the exhaust system time to fully warm up, often have extremely compromised exhaust systems, because the moisture simply can't be driven away effectively.
cars that make many short trips, which never give the exhaust system time to fully warm up, often have extremely compromised exhaust systems, because the moisture simply can't be driven away effectively.
Still crazy to think they drive through salted roads for a decade and are basically ok.
Btw were Deloreans pretty rust resistant? How will the cyber truck do living by the beach?
Btw were Deloreans pretty rust resistant? How will the cyber truck do living by the beach?
I went and googled the most obvious solutions I could think of for protecting rebar from rust.
- dipping rebar in epoxy is sometimes done, but a single nick in the coating causes all the erosion to concentrate in that one spot, so it can be more dangerous than just uncoated rebar
- galvanised rebar works much better than epoxy, and resists corrosion at lower pH levels than normal iron, but may result in more metal loss under some conditions
- sacrificial anodes (as per the article) can and are used, but exactly how is quite complicated: if they're embedded in the concrete, the zinc breaks down into substances that can weaken it
- concrete is naturally alkaline, with cement being manufactured partly from lime, and this protects the rebar, but too high a pH causes other problems in the concrete itself, so you can't just dump alkaline substances into the mixture forever
- you can apparently use fibreglass as rebar, but I have no idea if it's any good, or what happens to fibreglass if you leave it embedded in concrete for a century
- dipping rebar in epoxy is sometimes done, but a single nick in the coating causes all the erosion to concentrate in that one spot, so it can be more dangerous than just uncoated rebar
- galvanised rebar works much better than epoxy, and resists corrosion at lower pH levels than normal iron, but may result in more metal loss under some conditions
- sacrificial anodes (as per the article) can and are used, but exactly how is quite complicated: if they're embedded in the concrete, the zinc breaks down into substances that can weaken it
- concrete is naturally alkaline, with cement being manufactured partly from lime, and this protects the rebar, but too high a pH causes other problems in the concrete itself, so you can't just dump alkaline substances into the mixture forever
- you can apparently use fibreglass as rebar, but I have no idea if it's any good, or what happens to fibreglass if you leave it embedded in concrete for a century
If you can use fiberglass as rebar then maybe we could reuse/remanufacture wind turbine blades as rebar.
You are correct for certain definitions of 'stainless steel.' However as other comments have alluded to, some grades of 'stainless steel' will rust so slowly that they will survive orders of magnitude longer than recorded history. For example, some "Hyper-duplex" stainless steels are designed to resist corrosion in seawater that is above boiling point. This steel is probably not economical for building construction, but if you wanted it to last for millenia, it may be the optimal choice.
There's also basalt fiber reinforced concrete. Stronger than rebar and doesn't rust.
But steel's more ductile, so basalt-reinforcement failures are less gradual, providing less margin of safety or ability to patch repair (all things being equal). It's more similar to glass reinforcement (both available in bars, mats, and fibers), which is seeing increased use, but better than glass.
Good point. I've heard similar complaints about engineered wood (glulam and friends) for structures vs regular lumber. In fires, solid lumber fails gradually and makes lots of noises before it does, whereas engineered wood just goes BANG and fails at some point.
I don't think this stops these new products from being used, it's just another engineering tradeoff.
I don't think this stops these new products from being used, it's just another engineering tradeoff.
Stainless steel rebar is quite real, and becoming more common for bridges. It's essential for concrete exposed to salt water, which includes bridged de-iced with sale. Order now.[1][2]
There's epoxy-coated rebar, but that's on the way out. Quebec has already banned it. One scratch, water gets in, and corrosion starts. Also, the epoxy can be damaged by UV, like when there's a stack of rebar out in the sun.
[1] https://www.outokumpu.com/en/products/long-products/rebar
[2] https://stainlessrebar.com/
There's epoxy-coated rebar, but that's on the way out. Quebec has already banned it. One scratch, water gets in, and corrosion starts. Also, the epoxy can be damaged by UV, like when there's a stack of rebar out in the sun.
[1] https://www.outokumpu.com/en/products/long-products/rebar
[2] https://stainlessrebar.com/
To build on your very important last point. Material handling procedure is something that I haven't seen mentioned here that is a very real issue too. Similar to agriculture or pharma where entire stocks can be thrown out if stored incorrectly, in many construction and manufacturing contexts your steel can be thrown out for not being stored correctly too (i.e. left at the port in the open for extended periods, or mixed with other metals). Not just steel, but lots of building products (like membranes) will usually be specd with how they should be stored before use.
"This means that concrete structures, for all their stone-like superficial qualities, are actually made of the skeletons of sea creatures ground up with rock. It takes millions upon millions of years for these sea creatures to live, die and form into limestone. This timescale contrasts starkly with the life spans of contemporary buildings."
This description is fairly accurate. The CaCO3 (used as a source of calcium in the cement component of concrete) is completely decarbonated in a 1450°C kiln in the process of cement manufacture, combined with silica (from shale) +/- SO4 (from gypsum) and sintered to form an anhydrous calcium silicate (clinker: e.g. tricalcium silicate, Ca3SiO5, ‘alite’), then powdered (e.g. ordinary Portland cement, OPC). The skeletal limestone is long gone — and the above decarbonation step is the reason cement manufacturing process is a significant GHG source (in addition to fuel consumption by the kiln itself).
Mixing water with the powdered clinker generates a very rapid, exothermic, partial dissolution of the primary silicate. The rapid release of silica results in nucleation and growth of calcium silicate hydrate (CSH) plus Ca(OH)2. CSH binds the remaining unreacted solid mass together, giving cement its durability and strength.
This description is fairly accurate. The CaCO3 (used as a source of calcium in the cement component of concrete) is completely decarbonated in a 1450°C kiln in the process of cement manufacture, combined with silica (from shale) +/- SO4 (from gypsum) and sintered to form an anhydrous calcium silicate (clinker: e.g. tricalcium silicate, Ca3SiO5, ‘alite’), then powdered (e.g. ordinary Portland cement, OPC). The skeletal limestone is long gone — and the above decarbonation step is the reason cement manufacturing process is a significant GHG source (in addition to fuel consumption by the kiln itself).
Mixing water with the powdered clinker generates a very rapid, exothermic, partial dissolution of the primary silicate. The rapid release of silica results in nucleation and growth of calcium silicate hydrate (CSH) plus Ca(OH)2. CSH binds the remaining unreacted solid mass together, giving cement its durability and strength.
I don't know if it is really a problem, more like a tradeoff. Reinforced concrete costs less and enables shapes that are impossible without it, with the downside that the buildings last 50 years instead of 100+ years. The present value of a building that lasts 50 years is not that much different that the same one that lasts 100 years.
With that in mind, it makes perfect sense to make an office building out of reinforced concrete.
With that in mind, it makes perfect sense to make an office building out of reinforced concrete.
> The present value of a building that lasts 50 years is not that much different that the same one that lasts 100 years.
That's a problem in and of itself, IMO. Construction is tremendously resource-intensive. We should not be building "throwaway" buildings.
That's a problem in and of itself, IMO. Construction is tremendously resource-intensive. We should not be building "throwaway" buildings.
Not so straightforward. Sometimes we throw things away to make room for better things.
A - The concept of present value isn't a problem, it's more like a fact, derived from the time value of money. It's like saying gravity is a problem.
B - Construction is resource intensive, no doubt about it. Without this technique the costs and resources would go up, double?, more? Many structures we take for granted, like freeway overpasses, would be impossibly expensive.
B - Construction is resource intensive, no doubt about it. Without this technique the costs and resources would go up, double?, more? Many structures we take for granted, like freeway overpasses, would be impossibly expensive.
The classic problem is similar to that of that other famous future-proof thing: wifi in hotels. All the fancy hotels that got high-end wifi in the 2000s had shitty Internet for a long time because it was too hard to redo.
Sometimes, building to throw away is the best model. If something is so resource intensive in a way where the externalities are not appropriately mitigated, the right way is to tax the externalities, not to go after specific things.
If these builds were too expensive to build, they wouldn't be built.
Sometimes, building to throw away is the best model. If something is so resource intensive in a way where the externalities are not appropriately mitigated, the right way is to tax the externalities, not to go after specific things.
If these builds were too expensive to build, they wouldn't be built.
Although the hotels that hardwired RJ45 to each room are still going strong.
Right, they can stick APs in them. The point is that back then no one knew which tech would win and what tradeoff to make. Agility beats everything else except "guessing right".
For large institutions in the early 2000s, it was very obvious that Category 5 wiring and Ethernet was a difficult technology to beat. Even back then, most universities were running Ethernet to rooms in all new construction, and retrofitting spaces without it.
That infrastructure is still useful, 20 years on.
It isn't about agility or guessing right, it's about piloting attractive technologies (eg, small-scale DSL which uses existing phonelines, which was oftentimes a reliability nightmare), and keeping an eye to the future.
That infrastructure is still useful, 20 years on.
It isn't about agility or guessing right, it's about piloting attractive technologies (eg, small-scale DSL which uses existing phonelines, which was oftentimes a reliability nightmare), and keeping an eye to the future.
That's a bit like the one horse shay. It's not how long it lasts but what are the costs associated with it lasting any given length of time. Nothing lasts forever but say buildings lasted 500 years - Suddenly 500 years from now all buildings have to be replaced? And what's the cost of this 500 year building? Is it 10 times as much? Or is it 5 times as much?
Saying we shouldn't have buildings that only last 50 years but rather they should last 500 is like saying they shouldn't last 50 years but instead 5. Maybe. Maybe 5 makes sense.
My assumption would be - shocker - it's probably a complicated trade off that's best adjudicated by the people with the most skin in the particular game.
Saying we shouldn't have buildings that only last 50 years but rather they should last 500 is like saying they shouldn't last 50 years but instead 5. Maybe. Maybe 5 makes sense.
My assumption would be - shocker - it's probably a complicated trade off that's best adjudicated by the people with the most skin in the particular game.
I understand your reasoning. The problem is that this line is seldom used in the opposite direction.
You want a flimsy shell and to externalise the environmental impact? Sure thing, whatever the market will bear and is legal.
I think it is fair enough for people to put pressure on current practices. Zara and H&M will persist, but their customers should be and, thanks to outside voices, are now aware that social and environmental factors are involved in fast fashion.
Sure, it's arbitrary. But we still have alternatives. All else being equal, less entropy is better than more.
You want a flimsy shell and to externalise the environmental impact? Sure thing, whatever the market will bear and is legal.
I think it is fair enough for people to put pressure on current practices. Zara and H&M will persist, but their customers should be and, thanks to outside voices, are now aware that social and environmental factors are involved in fast fashion.
Sure, it's arbitrary. But we still have alternatives. All else being equal, less entropy is better than more.
> Suddenly 500 years from now all buildings have to be replaced? And what's the cost of this 500 year building? Is it 10 times as much? Or is it 5 times as much?
What a weird argument. It's obvious for multiple reasons that all buildings won't fail at the same time.
What a weird argument. It's obvious for multiple reasons that all buildings won't fail at the same time.
> That's a problem in and of itself, IMO. Construction is tremendously resource-intensive. We should not be building "throwaway" buildings.
If population levels change, up or down, we are going to have to be continually adjusting our usage of space to account for this. Making it easier to modify and/or tear-down-and-rebuild would make things a lot more efficient there. You'd need some policy changes too to fix the problems of, say, homeless people sleeping outside empty office buildings, but getting construction costs down would be a huge part of this.
We shouldn't be so arrogant to assume we are planning the right construction to serve us well for hundreds of years.
If population levels change, up or down, we are going to have to be continually adjusting our usage of space to account for this. Making it easier to modify and/or tear-down-and-rebuild would make things a lot more efficient there. You'd need some policy changes too to fix the problems of, say, homeless people sleeping outside empty office buildings, but getting construction costs down would be a huge part of this.
We shouldn't be so arrogant to assume we are planning the right construction to serve us well for hundreds of years.
If the buildings last a shorter amount of time, then more construction is needed which provides jobs. /s
“This is going to last 1000 years!”
…
“It only lasted 50”
…
“I don’t know if it is really a problem…”
It will become a very big problem if/when buildings start collapsing with people in them.
I grew up partly in an 18 story reinforced concrete building built in the 1920s. The apartment I lived in was recently sold for several million dollars.
Once, when there was a leak and the plaster came off, the underlying concrete was exposed and it scraped away like very weak sandstone.
How strong is the building and when will it collapse? Does anyone know? Is anyone testing?
I think the answer to both of those questions is "no". Everyone seems to assume they will stand forever. They won't.
I grew up partly in an 18 story reinforced concrete building built in the 1920s. The apartment I lived in was recently sold for several million dollars.
Once, when there was a leak and the plaster came off, the underlying concrete was exposed and it scraped away like very weak sandstone.
How strong is the building and when will it collapse? Does anyone know? Is anyone testing?
I think the answer to both of those questions is "no". Everyone seems to assume they will stand forever. They won't.
Unless you are living in a developing country, the answer to the second question should be "yes".
It should be but is it? I don't think anyone ever tested this building, which has a combined market value of probably close to $200M.
None of the owners want to know that their investments are worthless. So nothing will be checked unless its required by law.
None of the owners want to know that their investments are worthless. So nothing will be checked unless its required by law.
In Spain buildings older than 50 years are required to be inspected and mandated to make reforms if necessary. I doubt it's much different in the rest of Europe/north America
Also, buildings don't fall all of sudden. You would get a lot of cracks and problems before your building collapses
Also, buildings don't fall all of sudden. You would get a lot of cracks and problems before your building collapses
> Also, buildings don't [fail] all of sudden
They certainly do in earthquakes. Even in areas that nominally don’t have earthquakes, some parts of the building code will surely be about ability to withstand a rare earthquake.
They certainly do in earthquakes. Even in areas that nominally don’t have earthquakes, some parts of the building code will surely be about ability to withstand a rare earthquake.
... buildings don't fall all of sudden...
False.
Large structural failures can be catastrophic and unexpected.
Buildings can and do collapse quite suddenly. The examples here are not necessarily caused by reinforced concrete failures (though several cases make use of reinforced concrete --- generally other failures lead to the collapse). But the final failure of a system under load and near its structural limits can be quite sudden.
Taiwan bridge: https://youtube.com/watch?v=OSCPUGHUyIs https://youtube.com/watch?v=WqHXMswLwPM
Minnesota I35W bridge collapse: https://youtube.com/watch?v=CMdv2wRaqo4
Jerusalem dance floor: https://youtube.com/watch?v=5UOb7RBWlak
Morandi bridge, Italy: https://youtube.com/watch?v=V479srTBlAk
Hard Rock Hotel New Orleans (under construction): https://youtube.com/watch?v=WC8k5unvyfU
Sampoong Department Store, Korea (visualisation): https://youtube.com/watch?v=aQXTSR9koCg
The Kansas City Hyatt Regency skywalk collapse (1981) would be another instance. I don't believe there's video of the failure itself, though Grady from Practical Engineering has a great explainer of what went wrong: https://youtube.com/watch?v=VnvGwFegbC8
False.
Large structural failures can be catastrophic and unexpected.
Buildings can and do collapse quite suddenly. The examples here are not necessarily caused by reinforced concrete failures (though several cases make use of reinforced concrete --- generally other failures lead to the collapse). But the final failure of a system under load and near its structural limits can be quite sudden.
Taiwan bridge: https://youtube.com/watch?v=OSCPUGHUyIs https://youtube.com/watch?v=WqHXMswLwPM
Minnesota I35W bridge collapse: https://youtube.com/watch?v=CMdv2wRaqo4
Jerusalem dance floor: https://youtube.com/watch?v=5UOb7RBWlak
Morandi bridge, Italy: https://youtube.com/watch?v=V479srTBlAk
Hard Rock Hotel New Orleans (under construction): https://youtube.com/watch?v=WC8k5unvyfU
Sampoong Department Store, Korea (visualisation): https://youtube.com/watch?v=aQXTSR9koCg
The Kansas City Hyatt Regency skywalk collapse (1981) would be another instance. I don't believe there's video of the failure itself, though Grady from Practical Engineering has a great explainer of what went wrong: https://youtube.com/watch?v=VnvGwFegbC8
> None of the owners want to know that their investments are worthless. So nothing will be checked unless its required by law.
That makes no sense. If I am buying property, it is in my best interest to make sure it isn't going to fall apart. Especially since if something happened due to my negligence, I would be responsible.
If you have no idea of whether or not the building is being inspected, why would you make the assumption it's not?
That makes no sense. If I am buying property, it is in my best interest to make sure it isn't going to fall apart. Especially since if something happened due to my negligence, I would be responsible.
If you have no idea of whether or not the building is being inspected, why would you make the assumption it's not?
Once you’ve bought it, your incentives change no?
And ‘trust but verify’ is important - there are a lot of assumptions people make about what is actually checked or verified that are, well, just wrong. About a lot of things. And if you can’t find anyone saying it is happening, it very well might not be.
To the prior poster - call the NYC building department. Here is a link to their FAQ/index page and it should be straightforward to find from there. They are the ones responsible for making sure buildings don’t randomly collapse in NYC.
https://www1.nyc.gov/site/buildings/business/inspections.pag...
And ‘trust but verify’ is important - there are a lot of assumptions people make about what is actually checked or verified that are, well, just wrong. About a lot of things. And if you can’t find anyone saying it is happening, it very well might not be.
To the prior poster - call the NYC building department. Here is a link to their FAQ/index page and it should be straightforward to find from there. They are the ones responsible for making sure buildings don’t randomly collapse in NYC.
https://www1.nyc.gov/site/buildings/business/inspections.pag...
"First world country" does not correlate well with housing quality. UK has some of the worst housing in Europe, with 35% in need of repair. Many Ex Soviet states like Czech Repulbic are doing better.
UK also has a history of major failured in construction practices and inspection, where chunks of a new apartment block suddenly collapse like in Ronan Point, or a recently renovated tower block goes up in flames and half of residents die despite them warning about issues for years.
I wish living in first world country guaranteed sensible things are happening, but it doesn't
https://www.theguardian.com/environment/damian-carrington-bl... https://en.wikipedia.org/wiki/Ronan_Point https://en.wikipedia.org/wiki/Grenfell_Tower_fire
UK also has a history of major failured in construction practices and inspection, where chunks of a new apartment block suddenly collapse like in Ronan Point, or a recently renovated tower block goes up in flames and half of residents die despite them warning about issues for years.
I wish living in first world country guaranteed sensible things are happening, but it doesn't
https://www.theguardian.com/environment/damian-carrington-bl... https://en.wikipedia.org/wiki/Ronan_Point https://en.wikipedia.org/wiki/Grenfell_Tower_fire
> Does anyone know? Is anyone testing?
In first-world countries/states with earthquakes, the answer to this is often yes and yes.
A good article from 2000 in Christchurch discusses the issues: https://www.canterbury.ac.nz/media/documents/event/Hopkins-L...
The article is relevant because Christchurch had a major earthquake in 2011. I know of quite a few older buildings that were retrofitted that did not even need to be demolished (most buildings are designed to just survive a major earthquake, but often they need to be demolished due to damage, similar to writing off cars after accidents).
Christchurch did have regulatory failures because many older buildings were known to be unsafe (e.g. only meeting 10% of current code/regulations), but owners could defer fixing them up to code almost indefinitely. But that regulatory failure is being addressed in other parts of the country e.g. Wellington.
The South Island of New Zealand is overdue for a magnitude 8.2 Earthquake which will devastate many towns on the West Coast, and will affect the whole country indirectly. https://www.stuff.co.nz/the-press/news/90364889/magnitude82-...
You can sometimes see where concrete of a building has been tested for example a circular hole about 10cm across is left where a sample was taken.
If interested, next time you meet a civil engineer or someone working in the relevant department that deals with the building codes will often know relevant details about your location.
In first-world countries/states with earthquakes, the answer to this is often yes and yes.
A good article from 2000 in Christchurch discusses the issues: https://www.canterbury.ac.nz/media/documents/event/Hopkins-L...
The article is relevant because Christchurch had a major earthquake in 2011. I know of quite a few older buildings that were retrofitted that did not even need to be demolished (most buildings are designed to just survive a major earthquake, but often they need to be demolished due to damage, similar to writing off cars after accidents).
Christchurch did have regulatory failures because many older buildings were known to be unsafe (e.g. only meeting 10% of current code/regulations), but owners could defer fixing them up to code almost indefinitely. But that regulatory failure is being addressed in other parts of the country e.g. Wellington.
The South Island of New Zealand is overdue for a magnitude 8.2 Earthquake which will devastate many towns on the West Coast, and will affect the whole country indirectly. https://www.stuff.co.nz/the-press/news/90364889/magnitude82-...
You can sometimes see where concrete of a building has been tested for example a circular hole about 10cm across is left where a sample was taken.
If interested, next time you meet a civil engineer or someone working in the relevant department that deals with the building codes will often know relevant details about your location.
Yes, in known earthquake zones I would expect some testing, but in places like NYC I'm not sure.
In a few minutes searching I didn't find any reference to required testing of old buildings for structural or materials integrity.
In a few minutes searching I didn't find any reference to required testing of old buildings for structural or materials integrity.
In many parts of North America, testing and upgrades are only triggered with a change of use, or if required by buyers during sale of a building. The state does not maintain any kind of testing program of private buildings.
One exception is the mandatory retrofit programs implemented by some cities like San Francisco and Los Angeles.
One exception is the mandatory retrofit programs implemented by some cities like San Francisco and Los Angeles.
Having 1 in 25 buildings being completely rebuilt at all times and another 1 in ~5 getting renovations is extremely annoying.
I think buildings that are too regularly under construction should carry some tax penalties, instead renovating non-durable buildings to tastelessness is a way to save on property taxes, get tax deductions and try to pressure tenants out to get the latest upscale rates.
I think buildings that are too regularly under construction should carry some tax penalties, instead renovating non-durable buildings to tastelessness is a way to save on property taxes, get tax deductions and try to pressure tenants out to get the latest upscale rates.
Huh?
I spoke with a builder, and the concrete starts to decay in 50 years. Until then it's like new. It lasts much longer than that, 100+ years is not a problem.
I suggest the builder may have suffered from some motivated reasoning.
Concrete not starting to decay until 50 years has passed is the exception, not the rule.
Concrete not starting to decay until 50 years has passed is the exception, not the rule.
Only if you have poorly mixed concrete.
The kind of concrete they use in buildings is not the same as the concrete they use in sidewalks.
The kind of concrete they use in buildings is not the same as the concrete they use in sidewalks.
The problem, as per the article, isn't concrete. It's rusting steel inside reinforced concrete.
To be clear, the article is discussing reinforced concrete—concrete made with steel rebar, which rusts.
Unreinforced concrete can and does last for many hundred years. Reinforced concrete, not so much.
FTA:
“Early 20th-century engineers thought reinforced concrete structures would last a very long time – perhaps 1,000 years. In reality, their life span is more like 50-100 years, and sometimes less. Building codes and policies generally require buildings to survive for several decades, but deterioration can begin in as little as 10 years.”
Unreinforced concrete can and does last for many hundred years. Reinforced concrete, not so much.
FTA:
“Early 20th-century engineers thought reinforced concrete structures would last a very long time – perhaps 1,000 years. In reality, their life span is more like 50-100 years, and sometimes less. Building codes and policies generally require buildings to survive for several decades, but deterioration can begin in as little as 10 years.”
We only use reinforced concrete. The type of work where simple concrete is enough are very rare.
It may start to lose it's strength after 50 years, as designed, if kept under designated conditions.
As for decay, IIUC, it loses pH gradually, from the time you mix it, and that pH is the most important protecting factor that stops the steel from rusting.
Obviously though, a lot of factors have a huge factor on lifetime, including composition, construction, environmental conditions ...
As for decay, IIUC, it loses pH gradually, from the time you mix it, and that pH is the most important protecting factor that stops the steel from rusting.
Obviously though, a lot of factors have a huge factor on lifetime, including composition, construction, environmental conditions ...
Simple concrete is enough in almost all cases for what we do - if we use enough of it. Rebar allows dramatically reducing the amount we use in most cases, with this predictable trade off
It’s rarely physics, almost always economics.
It’s rarely physics, almost always economics.
Plain concrete is simply not allowed by code for many applications. So even if you could theoretically justify the design, you couldn’t get the permit to build it.
Physics, economics, and bureaucratics is a good summary of structural engineering. The last one can’t be ignored.
Physics, economics, and bureaucratics is a good summary of structural engineering. The last one can’t be ignored.
Unreinforced concrete is largely useless for modern construction, because it basically has negligible tensile strength. You can't make beams, columns, or even pre-fabbed wall panels of any useful strength without reinforcement.
One of the reasons unreinforced concrete may last a lot longer is because its only going to exist in places that don't subject it to tensile stresses. That being said, changes like differential settling can create these stresses after construction.
'Deterioration' can mean many things in terms of concrete.
One of the reasons unreinforced concrete may last a lot longer is because its only going to exist in places that don't subject it to tensile stresses. That being said, changes like differential settling can create these stresses after construction.
'Deterioration' can mean many things in terms of concrete.
With 30 year fixed rate mortgages at 3%, I'd say the present value of a building that lasts 100 years is 23% more than the present value of a building that lasts 50 years. It's certainly worth it to spend more for a longer lasting building.
Reinforced concrete has achieved regulatory capture via the building codes. If you try to build with anything non-standard, prepare to deal with a mountain of red tape.
Given past "innovations" in the space of building materials, I think this is just about the last place people should be complaining about needing to comply with regulations...
And in fact it seems that one attempted fix to the corrosion problem, epoxy-coated rebar, has already proven much worse than uncoated rebar at dealing with rust in production: https://www.youtube.com/watch?v=xVDy84rR5Z8
(That, BTW, is from a channel devoted to concrete made by a civil-engineering academic who specialises in the stuff https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ )
(That, BTW, is from a channel devoted to concrete made by a civil-engineering academic who specialises in the stuff https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ )
I'm not sure this article does a good job of highlighting "the problem with reinforced concrete" than it does "the better attributes of material x with y over concrete". Reinforced concrete seems to do exactly what it's intended to do for the designed life of that intent, with some very well known trade-offs coupled with some brilliant strengths.
Sure, compared to other materials it might not be as: long-lasting, cheap, sustainable, but as in all things it seems one can only pick two.
Sure, compared to other materials it might not be as: long-lasting, cheap, sustainable, but as in all things it seems one can only pick two.
> Reinforced concrete seems to do exactly what it's intended to do for the designed life of that intent
Until there's apparently "no money" to replace the structure after its design life time. Thinking in decades of life span for many of these structures is very short sighted. I think the article mostly gets that across i.e. re-enforced concrete is hard to recycle and their life span is often within that of a human life. We should be able to do better and create large scale structures that can not only serve a purpose over several life times, but can be added to or enhanced rather than demolished.
The only reason we keep building these time limited structures is because building codes still allow this, which leads to easy short term profits, and it's "someone else's problem in 50-60 years time". There's no incentives.
Until there's apparently "no money" to replace the structure after its design life time. Thinking in decades of life span for many of these structures is very short sighted. I think the article mostly gets that across i.e. re-enforced concrete is hard to recycle and their life span is often within that of a human life. We should be able to do better and create large scale structures that can not only serve a purpose over several life times, but can be added to or enhanced rather than demolished.
The only reason we keep building these time limited structures is because building codes still allow this, which leads to easy short term profits, and it's "someone else's problem in 50-60 years time". There's no incentives.
Municipal and other budgets are already highly strained all over. If the cost of an interchange or large culvert goes up 2x to increase its lifespan, you can do less work now. Your level of service goes down now.
There are trade offs to everything. Build something much more durable, pay twice as much, do half the work in a season and get more complaints. We already aim to build infrastructure based on estimates of future loading - how much traffic, what kind of trucks at what weight, etc.
We'd all be much better off increasing maintenance budgets to extend the lifespan of existing structures without completely re-doing them at multiples of the current price.
There are trade offs to everything. Build something much more durable, pay twice as much, do half the work in a season and get more complaints. We already aim to build infrastructure based on estimates of future loading - how much traffic, what kind of trucks at what weight, etc.
We'd all be much better off increasing maintenance budgets to extend the lifespan of existing structures without completely re-doing them at multiples of the current price.
Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction.
Saving a little on the upfront cost only to pay a lot more for maintenance is a false economy. Stainless steel rebar does not double the cost of construction, and neither does high quality concrete.
We need to stop buying subscribtion to "bridge as a service"
Saving a little on the upfront cost only to pay a lot more for maintenance is a false economy. Stainless steel rebar does not double the cost of construction, and neither does high quality concrete.
We need to stop buying subscribtion to "bridge as a service"
> Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction.
You have it exactly backwards - most of the budget goes to capital construction - replacement of existing structures and roads. The maintenance budget is constantly shrunk.
>Stainless steel rebar does not double the cost of construction, and neither does high quality concrete.
Last I checked stainless rebar was ~3x the cost of regular rebar...
"high quality" concrete doesn't mean anything. Most concrete is high quality.
>We need to stop buying subscribtion to "bridge as a service"
All infrastructure requires maintenance and eventual replacement. Bridges will never be permanent and will always require regular inspection, maintenance, etc.
You have it exactly backwards - most of the budget goes to capital construction - replacement of existing structures and roads. The maintenance budget is constantly shrunk.
>Stainless steel rebar does not double the cost of construction, and neither does high quality concrete.
Last I checked stainless rebar was ~3x the cost of regular rebar...
"high quality" concrete doesn't mean anything. Most concrete is high quality.
>We need to stop buying subscribtion to "bridge as a service"
All infrastructure requires maintenance and eventual replacement. Bridges will never be permanent and will always require regular inspection, maintenance, etc.
"Last I checked stainless rebar was ~3x the cost of regular rebar"
But it's 5-10% of the total building cost, and if you bump that to 20% the corrosion goes from "always' to "probably never"
But it's 5-10% of the total building cost, and if you bump that to 20% the corrosion goes from "always' to "probably never"
if you need to weld the rebar into cages (like you often do) then the cost goes up even more as welding ss is harder.
But you're not wrong in general. There will still be corrosion in the concrete eventually but less likely from rebar oxidation.
But you're not wrong in general. There will still be corrosion in the concrete eventually but less likely from rebar oxidation.
Welding rebar is almost never used in North American building construction, and is actually forbidden in high seismic zones.
But then again so is stainless steel rebar and carbon fibre rebar and most of these other types of products because they lack ductility
But then again so is stainless steel rebar and carbon fibre rebar and most of these other types of products because they lack ductility
This is kind of what I was thinking while reading comments here.
I'm sure stainless rebar is easy to make. We could turn out huge amounts of it. But I don't see it ever having the same useful properties. All manner of stainless I've worked with is incredibly stiff and hard compared to regular steel. It's actually desirable in most applications, but rebar in particular needs to be flexible.
I'm sure stainless rebar is easy to make. We could turn out huge amounts of it. But I don't see it ever having the same useful properties. All manner of stainless I've worked with is incredibly stiff and hard compared to regular steel. It's actually desirable in most applications, but rebar in particular needs to be flexible.
I think many commentators, including yourself, have an erroneous assumption about structural design which is roughly summarized as: the inputs are known with certainty. This is really not the case especially when considering natural hazards like wind and earthquake. What happens to your 500 year lifespan design when we discover new information about earthquakes at the site. This is happening regularly with every building code update. Our design loads change To reflect the latest research on things like seismicity. When you factor in this consideration, it may actually make a lot of sense to only design for shorter lifespans.
Every human is valuable. Every human has opinions. But every human’s opinions are not equally valuable.
Their are two reasons for steel reinforcing. The steel can withstand tension and concrete can’t. Even worse concrete in tension fails catastrophically, the steel insures it fails ductally.
Masonry had exactly the same problems and all modern masonry structures are reinforced masonry...reinforced with steel, Just like concrete.
Aluminum and other potential reinforcement materials are less suited than steel because steel and concrete have similar coefficients of thermal expansion. Yes steel can corrode and expand and spall concrete. Other materials will spall concrete simply from seasonal and diurnal changes in temperature.
Concrete designs are engineered and like all engineered systems, there are trade offs between cost and performance. And like any design, use may exceed or deviate from specified design parameters.
Their are two reasons for steel reinforcing. The steel can withstand tension and concrete can’t. Even worse concrete in tension fails catastrophically, the steel insures it fails ductally.
Masonry had exactly the same problems and all modern masonry structures are reinforced masonry...reinforced with steel, Just like concrete.
Aluminum and other potential reinforcement materials are less suited than steel because steel and concrete have similar coefficients of thermal expansion. Yes steel can corrode and expand and spall concrete. Other materials will spall concrete simply from seasonal and diurnal changes in temperature.
Concrete designs are engineered and like all engineered systems, there are trade offs between cost and performance. And like any design, use may exceed or deviate from specified design parameters.
Tangentially related. This company using graphene laced concrete to reduce the amount of cement required. And eliminating steel. New product called "Concretene".
[0]https://twitter.com/Paul_Denney/status/1397132479144812544
[1]https://www.punchline-gloucester.com/articles/aanews/glouces...
[0]https://twitter.com/Paul_Denney/status/1397132479144812544
[1]https://www.punchline-gloucester.com/articles/aanews/glouces...
> graphene
Graphene has its own set of problems. Namely, it can be toxic to humans. [1] And who knows what massive quantities of graphene in concrete will do to an environment 10-20 years after the building's construction. Even demolition with explosives will probably be problematic due to potentially massive clouds of nanoparticles it could create.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039077/
Graphene has its own set of problems. Namely, it can be toxic to humans. [1] And who knows what massive quantities of graphene in concrete will do to an environment 10-20 years after the building's construction. Even demolition with explosives will probably be problematic due to potentially massive clouds of nanoparticles it could create.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039077/
Graphene isn't persistent though - it burns.
So does plastic.
In the context of building materials that's not a good thing
> Namely, it can be toxic to humans
Uhhhh the rest of the stuff in Concrete isn't great for human health, either, or as my cousin likes to say, "it sure ain't vitamins."
Quartz dust and silica sand are really bad for the lungs, likely carcinogens. Lime is caustic. Dust in general is bad to breathe.
These are well-known hazards in demolition and mitigation techniques already exist.
Uhhhh the rest of the stuff in Concrete isn't great for human health, either, or as my cousin likes to say, "it sure ain't vitamins."
Quartz dust and silica sand are really bad for the lungs, likely carcinogens. Lime is caustic. Dust in general is bad to breathe.
These are well-known hazards in demolition and mitigation techniques already exist.
I never said it was. I'm saying that adding carbon nonoparticles will only make matters much worse.
The contractor I used on a remodel spoke of carbon fiber reinforced concrete, which I googled, and it's called "carboconcrete". It is described as, "a highly stressable lightweight composite construction that combines special fine grain ultra high-strength concrete and carbon fibers."
Fiber-reinforced cement composites are an interesting alternative:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/suco.2017001...
Some German researchers seem to think that carbon fiber-reinforced polymer "rebar" could be more durable than steel bars with similar cost and lower weight:
https://www.aboutcivil.org/carbon-reinforced-concrete-buildi...
Unfortunately, the terminology is not well standardized, and when you look up "carbon fiber reinforced concrete", you never know if you're going to get a fiber-reinforced cement composite (incorporating carbon fibers directly into the cement matrix) or a CFRP rebar system. Regardless, there do seem to be some improvements on the horizon.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/suco.2017001...
Some German researchers seem to think that carbon fiber-reinforced polymer "rebar" could be more durable than steel bars with similar cost and lower weight:
https://www.aboutcivil.org/carbon-reinforced-concrete-buildi...
Unfortunately, the terminology is not well standardized, and when you look up "carbon fiber reinforced concrete", you never know if you're going to get a fiber-reinforced cement composite (incorporating carbon fibers directly into the cement matrix) or a CFRP rebar system. Regardless, there do seem to be some improvements on the horizon.
Lightweight video.
https://www.youtube.com/watch?v=nB9ViglDMmg
An interesting read, albeit with information that is likely familiar to many. Given the issues surrounding concrete with greenhouse gases, recycling, and landfill contribution, it seems that timber (https://arstechnica.com/information-technology/2012/05/wood-...) may actually be a more viable alternative. We have techniques to grow it sustainably, it can be a carbon sink within a city, and it is mostly natural wood so it can decompose.
As an economics exercise, it may also be interesting to price in the cost of dismantling/disposing of construction materials into the initial construction cost. I wonder if doing so will steer materials development away from composites that are difficult to recycle towards something new.
As an economics exercise, it may also be interesting to price in the cost of dismantling/disposing of construction materials into the initial construction cost. I wonder if doing so will steer materials development away from composites that are difficult to recycle towards something new.
This is the only post I found mentioning recycling, and I think that's a key factor in this all. My generation is going to be the first saddled with a lot of old buildings we have to deal with. We are going to have to get good at recycling buildings.
My understanding that the economics have already really pushed us massively forwards in the past decade or two, that we are far more aggressive about recycling construction aggregate[1].
The article has a nod midway through to these concerns,
> The many alternative materials for concrete reinforcement – such as stainless steel, aluminium bronze and fibre-polymer composites – are not yet widely used. The affordability of plain steel reinforcement is attractive to developers. But many planners and developers fail to consider the extended costs of maintenance, repair or replacement.
This definitely seems like a huge societal blind-side to me. As much as it's an issue of planners and developers, I feel like there's a consumer lack of understanding. The invisible hand can't push effectively here, can't reward the builders doing it right adequately. In part because society is not aware, doesn't know what to ask for, doesn't have standards, doesn't view & comprehend the role of maintenance & ultimately recycling. These are far off things.
As my generation starts to see the limits of sustainability, see where so very many many creations begin to become risks & hazards & losses rather than values, we may develop some sense, but switching over into a fear-based emotional reaction isn't necessarily a great fix. Trying to give us all a picture of the life-cycle, the costs, the trade-offs; that seems like the necessary task. Regulating our ability to see & ascertain.
Hopefully we just get better & better about recycling. It'd be so interesting to see how reinforcements are extracted from construction aggregate today. Stainless steel reinforcement isn't expensive... if you can safely view it not as a sunk construction cost, but as a semi-long term loan for a building. Where-as more advanced materials like fiber-polymer, I tend to imagine, may have wonderful characteristics in use, I also tend to imagine them as likely having less recoverability. Steel: material we know how to re-cast.
[1] https://en.wikipedia.org/wiki/Concrete_recycling
My understanding that the economics have already really pushed us massively forwards in the past decade or two, that we are far more aggressive about recycling construction aggregate[1].
The article has a nod midway through to these concerns,
> The many alternative materials for concrete reinforcement – such as stainless steel, aluminium bronze and fibre-polymer composites – are not yet widely used. The affordability of plain steel reinforcement is attractive to developers. But many planners and developers fail to consider the extended costs of maintenance, repair or replacement.
This definitely seems like a huge societal blind-side to me. As much as it's an issue of planners and developers, I feel like there's a consumer lack of understanding. The invisible hand can't push effectively here, can't reward the builders doing it right adequately. In part because society is not aware, doesn't know what to ask for, doesn't have standards, doesn't view & comprehend the role of maintenance & ultimately recycling. These are far off things.
As my generation starts to see the limits of sustainability, see where so very many many creations begin to become risks & hazards & losses rather than values, we may develop some sense, but switching over into a fear-based emotional reaction isn't necessarily a great fix. Trying to give us all a picture of the life-cycle, the costs, the trade-offs; that seems like the necessary task. Regulating our ability to see & ascertain.
Hopefully we just get better & better about recycling. It'd be so interesting to see how reinforcements are extracted from construction aggregate today. Stainless steel reinforcement isn't expensive... if you can safely view it not as a sunk construction cost, but as a semi-long term loan for a building. Where-as more advanced materials like fiber-polymer, I tend to imagine, may have wonderful characteristics in use, I also tend to imagine them as likely having less recoverability. Steel: material we know how to re-cast.
[1] https://en.wikipedia.org/wiki/Concrete_recycling
As a point of interest, recycled concrete is referred to as "urbanite".
https://www.concretenetwork.com/concrete/demolition/urbanite...
It's definitely a case of downcycling, though: there's a lot less we can do with urbanite than with cement and aggregate in their original forms.
https://www.concretenetwork.com/concrete/demolition/urbanite...
It's definitely a case of downcycling, though: there's a lot less we can do with urbanite than with cement and aggregate in their original forms.
"I feel like there's a consumer lack of understanding. The invisible hand can't push effectively here"
When I asked the real estate agent what's the expected lifespan of a house, she looked at me like she's just seen an alien. In fact, half the time, they don't even get the floor space right and every floor plan comes with a disclaimer "maybe this is wrong"
When I asked the real estate agent what's the expected lifespan of a house, she looked at me like she's just seen an alien. In fact, half the time, they don't even get the floor space right and every floor plan comes with a disclaimer "maybe this is wrong"
Yes, I've heard about engineered timber - https://blog.i1machines.com/four-reasons-why-engineered-timb... - I'm no expert, but it sounds like one of the better alternatives to reinforced concrete. Among its many benefits, it theoretically has a much longer lifespan than reinforced concrete.
I work right next to a seven-storey office building in Sydney, that's built almost entirely with engineered timber - https://architectureau.com/articles/australias-first-commerc... - ever bigger and taller such buildings are going up, bit by bit, around the world.
I work right next to a seven-storey office building in Sydney, that's built almost entirely with engineered timber - https://architectureau.com/articles/australias-first-commerc... - ever bigger and taller such buildings are going up, bit by bit, around the world.
Rusting is not the only reason for reinforced concrete to crack and fail.
The concrete and steel have different thermal expansion meaning that, over time, the concrete is bound to develop cracks if there are any changes in temperature.
Another reason why modern structures crack and disintegrate is because they tend to be built from rather large blocks. Whereas old structures were composed from single bricks or stones. The way these were built meant that the structure would crack in multiple places in a way that would allow the movement to be absorbed and distributed throughout the structure and be more easily repaired. See this guy explain it much better than I could: https://www.youtube.com/watch?v=p5qVxAoKwbE
The concrete and steel have different thermal expansion meaning that, over time, the concrete is bound to develop cracks if there are any changes in temperature.
Another reason why modern structures crack and disintegrate is because they tend to be built from rather large blocks. Whereas old structures were composed from single bricks or stones. The way these were built meant that the structure would crack in multiple places in a way that would allow the movement to be absorbed and distributed throughout the structure and be more easily repaired. See this guy explain it much better than I could: https://www.youtube.com/watch?v=p5qVxAoKwbE
No mention of epoxy coatings for steel rebar? Look for green-coated rebar as you pass highway construction sites.
There’s also hot-dip galvanized and stainless steel rebar.
... with stainless being a much better (but much more expensive) choice.
HD Galvanized is a coating whereas stainless steel is a different material - it is stainless all the way through ...
HD Galvanized is a coating whereas stainless steel is a different material - it is stainless all the way through ...
It's a coating, but my understanding is that it basically creates a battery that keeps the nearby iron from deteriorating. Small gaps in the coating therefore don't really matter as long as there is still some zinc nearby.
Like zinc anodes on a boat?
Yep, I believe that's the same mode of operation. The definition of galvanic is, "relating to or involving electric currents produced by chemical action."
Epoxy coating is falling out of favour, as it has two downsides: 1) is has a weaker bond to the concrete, so you need longer bars to transfer the force, and 2) if it gets damaged (scratched or cut), the corrosion will concentrate at that location, and you are more likely to end up with a fully rusted-through bar, as opposed to a small amount of corrosion spread over the whole bar.
Reinforced concrete is much like clothing: a stitch in time saves nine. With regular cleaning and maintenance, it can last much longer than if you just let it deteriorate.
Reinforced concrete is much like clothing: a stitch in time saves nine. With regular cleaning and maintenance, it can last much longer than if you just let it deteriorate.
For some reason I stumbled across a wild YouTube channel by a guy named Tyler Ley that is “crazy for concrete”. If I remember correctly he’s a civil engineering professor and has a lot of fascinating videos about concrete.
In particular one about epoxy coated rebar that gives interesting notes about why it has its problems: https://youtu.be/xVDy84rR5Z8
I had a great couple of days learning all about the complexities of concrete through his videos.
In particular one about epoxy coated rebar that gives interesting notes about why it has its problems: https://youtu.be/xVDy84rR5Z8
I had a great couple of days learning all about the complexities of concrete through his videos.
That certainly helps, but in some cases such as when the rebar is under tension the epoxy coating can result in unexpected failure if there is any damage to it. The small areas lacking coating are corroded more aggressively, resulting in deep pitting which can weaken the bar to the point of failure.
It's pretty dependent on skilled people using it, every ding must be properly repainted before the concrete is poured, so extra care must be taken transporting and laying it.
https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galv... has a lot more, but clearly not a panacea...
https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galv... has a lot more, but clearly not a panacea...
The article makes only a glossed-over mention of fiberglass rebar, which is about 1/7th the weight of steel, faster to install, creates no EM issues, does not rust and costs less. Here's some examples, admittedly from those selling it [1][2], and from other news/ industry sources [3]. also, other fibers such as basalt provide even better properties [4].
All it takes is for architects and engineers to get their heads around new technologies and start specifying better materials. This wouldn't fully solve the CO2 problem of concrete, but it would reduce it by making each ton of concrete last a lot longer.
[1] https://www.owenscorning.com/en-us/composites/pinkbar-vs-ste...
[2] https://www.tuf-bar.com/5-reasons-why-you-should-use-fibergl...
[3] https://www.globalspec.com/learnmore/building_construction/b...
[4] https://www.forconstructionpros.com/concrete/equipment-produ...
All it takes is for architects and engineers to get their heads around new technologies and start specifying better materials. This wouldn't fully solve the CO2 problem of concrete, but it would reduce it by making each ton of concrete last a lot longer.
[1] https://www.owenscorning.com/en-us/composites/pinkbar-vs-ste...
[2] https://www.tuf-bar.com/5-reasons-why-you-should-use-fibergl...
[3] https://www.globalspec.com/learnmore/building_construction/b...
[4] https://www.forconstructionpros.com/concrete/equipment-produ...
Tangentially related. The romans figured out that volcanic ash and salty sea water made cement that actually gets stronger with age instead of breaking-down after 50 years: https://www.sciencemag.org/news/2017/07/why-modern-mortar-cr...
I'm not sure, but this probably fits the facts better: the Romans figured out how to make cement with volcanic ash and salty sea water, and it turns out that it gets stronger with age.
It's not clear to me that the Romans knew that, or that it informed their choice of that building material. I suspect it's more that they built with what they had, and got lucky that it turns out to be incredibly durable stuff.
It's not clear to me that the Romans knew that, or that it informed their choice of that building material. I suspect it's more that they built with what they had, and got lucky that it turns out to be incredibly durable stuff.
The Roman scholar Pliny the Elder described underwater concrete structures that become "a single stone mass, impregnable to the waves and every day stronger."
https://www.nature.com/news/seawater-is-the-secret-to-long-l...
Sounds like they knew.
https://www.nature.com/news/seawater-is-the-secret-to-long-l...
Sounds like they knew.
At least those samples to be mixed just right to survive over 1,000 years had a mixture that got stronger with age. There's a big element of survivorship bias.
Also, due to a lack of reinforcement, Roman concrete structures, at least those that survived, avoided putting concrete in tension. Roman concrete won't last very long in areas of buildings that are under tension. Edit: the implication being that using Roman concrete would make many modern building designs unworkable, particularly taller thinner designs that sway a bit in the wind.
Also, due to a lack of reinforcement, Roman concrete structures, at least those that survived, avoided putting concrete in tension. Roman concrete won't last very long in areas of buildings that are under tension. Edit: the implication being that using Roman concrete would make many modern building designs unworkable, particularly taller thinner designs that sway a bit in the wind.
Left out is the reason we don't use the Roman mix today: it takes years for the concrete to set; Roman concrete is weaker for the first decade compared to modern cement mixes.
Moreover, back in Roman times, Roman concrete was not as strong back as it is today. As the article you linked points out, "Because both minerals take centuries to strengthen concrete, modern scientists are still working on recreating a modern version of Roman cement."
Moreover, back in Roman times, Roman concrete was not as strong back as it is today. As the article you linked points out, "Because both minerals take centuries to strengthen concrete, modern scientists are still working on recreating a modern version of Roman cement."
Very good point. Most building projects actually use admixtures to get as rapid strength increase as possible, even if it means less strength increase long term, because the early strength determines when you can strip formwork and start building the next floor. Builders want concrete reaching ~18MPA in like <2 days.
imagine a world where new houses are cheaper and as it ages and surrounding develops houses become more desirable and stronger
I took an engineering course on concrete 30 year ago. There were a lot of additives and techniques described which improve various properties but it seems like 30 years later cost is the biggest consideration.
Guessing at "the problem" before reading the piece, I figured it would be that it's weak in tension. Not quite what they said, but that does happen to be the reason you need rebar in the first place.
Concrete however does an excellent job of externalizing its costs: into the atmosphere, forward through time, and onto other people. So it will remain popular so long as those remain the expressed values of society.
Edit: Awww, boo hoo!
Concrete however does an excellent job of externalizing its costs: into the atmosphere, forward through time, and onto other people. So it will remain popular so long as those remain the expressed values of society.
Edit: Awww, boo hoo!
Surely this could be the moment for glass fiber reinforced concrete to take center stage. It really should just last forever.
My understanding is that alkali-resistant glass is required, but the 18% ZrO2 used means that it isn't much cheaper than using carbon fiber, which seems to have slowly taken over. But GFRC is bright white, while carbon fiber makes a greyish product, so the former is preferred for decoration.
I wrote a concrete corrosion simulation as part of my graduate research. You can use it at corrosion.smcf.io
It's also important to note that not all medieval and historic structures survived the test of time. A case of Survival-Bias. As the utility requirements of the structure may change over time,there is no incentive for engineers and clients to design a structure that would last more than 50-100 years. As far as the current building design provisions and policies go by, rebar does it's job.
What needs intervention is to find a suitable replacement for concrete/cement citing it's increasing contribution to global warming.
What needs intervention is to find a suitable replacement for concrete/cement citing it's increasing contribution to global warming.
> Given the survival of ancient structures,
Survivorship bias...
Survivorship bias...
There are also interesting new methods to monitor corrosion
They fairly regularly do localized repair on some structures (e.g. bridge/overpass).
Yes, why wouldn’t you be able to repair replace parts of a building? You cut out the bad parts while reinforcing structural elements temporarily while the replacement work is performed, then you remove the temp supports.
New footings, beams, walls, etc are constructed or installed to replace old ones all the time.
Say you have a bad concrete footing for a post. You use jacks to support the beam on both sides of the post that sits on the footing, remove the post, remove the footing, pour a new footing, and then put a new post in and remove the beam jacks.
New footings, beams, walls, etc are constructed or installed to replace old ones all the time.
Say you have a bad concrete footing for a post. You use jacks to support the beam on both sides of the post that sits on the footing, remove the post, remove the footing, pour a new footing, and then put a new post in and remove the beam jacks.
I saw this done in downtown SF to the old macy's men's building. they cut off the facade, cut the concrete back a bit but left the old rebar protruding some and grafted new concrete/rebar on to it.
Once you know about spalling, you see it everywhere. There's a train bridge straddling a high-traffic road in Philadelphia that is crumbling year after year, and I think the freight company that owns it still hasn't done anything about it. We just have to hope there's no traffic when it eventually fails.
If owners were willing to pay for it, or the government wanted it to happen via the Standards then contractors would build it.
Doesn't change the building process at all, just where they procure from.
Doesn't change the building process at all, just where they procure from.
There's nothing wrong with reinforced concrete, but the incentives to produce long lasting buildings are not there. The cheapest bidder will generally win and their building will last the "design life" of the building, but often not much more. The simplest way to change this is to extend the design life, which would result in stainless steels or another more expensive material being used in this application.