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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#121

Post by labawi »

GoToRO wrote: post #92
oxfeed65261 wrote: post #69

Earlier quoted context omitted.

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…

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 ...

Re: The problem with reinforced concrete (2016)

#122

Post by LegitShady »

teh_klev wrote: post #58
ajcp wrote: post #25

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, che…

> 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 l…

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.

Re: The problem with reinforced concrete (2016)

#123

Post by toss1 »

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...

Re: The problem with reinforced concrete (2016)

#124

Post by geoffmunn »

rootusrootus wrote: post #96
0xbadcafebee wrote: post #37

Earlier quoted context omitted.

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…

> 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…

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.

Re: The problem with reinforced concrete (2016)

#125

Post by culturestate »

WalterBright wrote: post #116
culturestate wrote: post #114

Earlier quoted context omitted.

> 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 n…

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 d…

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.

Re: The problem with reinforced concrete (2016)

#126

Post by sokoloff »

LoveMortuus wrote: post #105
mardifoufs wrote: post #74

Earlier quoted context omitted.

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 fut…

Word tip: “cease to exist” rather than “seize”

Re: The problem with reinforced concrete (2016)

#127

Post by Animats »

brutusborn wrote: post #3

This should be an economics piece, not an environmental piece. The author states that "one of iron’s unalterable properties is that it rusts" yet further on acknowledges the existence of stainless steel. 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 buildin…

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/

Re: The problem with reinforced concrete (2016)

#128

Post by lazide »

dntrkv wrote: post #110
raylad wrote: post #48

Earlier quoted context omitted.

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. 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…

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...

Re: The problem with reinforced concrete (2016)

#129

Post by sokoloff »

dan-robertson wrote: post #97
Taek wrote: post #34

Earlier quoted context omitted.

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 negati…

> 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.

Re: The problem with reinforced concrete (2016)

#130

Post by lazide »

GoToRO wrote: post #92
oxfeed65261 wrote: post #69

Earlier quoted context omitted.

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…

We only use reinforced concrete. The type of work where simple concrete is enough are very rare.

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.

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