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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#181

Post by kortex »

readflaggedcomm wrote: post #109
kortex wrote: post #81

Earlier quoted context omitted.

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.

Re: The problem with reinforced concrete (2016)

#182

Post by peteradio »

sgillen wrote: post #72
peteradio wrote: post #64

Earlier quoted context omitted.

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...

Maybe if you want to invalidate those studies you can try leaving the knives out in the rain 10-100 days in a row!

In fact we lost the kitchen shears from the set for half a year, no rust.

Re: The problem with reinforced concrete (2016)

#183

Post by brutusborn »

wahern wrote: post #29
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…

> 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 .

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.

Re: The problem with reinforced concrete (2016)

#184

Post by lurquer »

bombcar wrote: post #80
lurquer wrote: post #51

Earlier quoted context omitted.

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.

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?

Re: The problem with reinforced concrete (2016)

#185

Post by lamontcg »

rsa4046 wrote: post #169
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…

"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 i…

Yeah that section seemed like creative writing and stretching for a metaphor. Kind of detracted from the overall point about rusting infrastructure.

Re: The problem with reinforced concrete (2016)

#186

Post by alliao »

gamblor956 wrote: post #83
ConcernedCoder wrote: post #33

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...

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…

imagine a world where new houses are cheaper and as it ages and surrounding develops houses become more desirable and stronger

Re: The problem with reinforced concrete (2016)

#187

Post by rm445 »

lurquer wrote: post #51
minikites wrote: post #4

Earlier quoted context omitted.

Is it a good thing for society to directly incentivize the construction of longer lasting buildings?

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.

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.

Re: The problem with reinforced concrete (2016)

#188

Post by LoveMortuus »

sokoloff wrote: post #126
LoveMortuus wrote: post #105

Earlier quoted context omitted.

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”

Now that you said it, it totally makes sense, because too seize, means to take away as in: The police seized my laptop. Thanks ^^

Re: The problem with reinforced concrete (2016)

#189

Post by dredmorbius »

diegocg wrote: post #65
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.

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

... 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

Re: The problem with reinforced concrete (2016)

#190

Post by sjg007 »

strken wrote: post #141
wahern wrote: post #29

Earlier quoted context omitted.

> 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 .

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 lo…

If you can use fiberglass as rebar then maybe we could reuse/remanufacture wind turbine blades as rebar.
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