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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#91

Post by mdgrech23 »

quickthrowman wrote: post #50
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 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 proj…

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.

Re: The problem with reinforced concrete (2016)

#92

Post by GoToRO »

oxfeed65261 wrote: post #69
GoToRO wrote: post #40

Earlier quoted context omitted.

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.

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.

Re: The problem with reinforced concrete (2016)

#93

Post by frosted-flakes »

sgtnoodle wrote: post #44
rsync wrote: post #13

Earlier quoted context omitted.

... 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 ...

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?

Re: The problem with reinforced concrete (2016)

#95

Post by leoc »

Jweb_Guru wrote: post #66
opwieurposiu wrote: post #6

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 )

Re: The problem with reinforced concrete (2016)

#96

Post by rootusrootus »

0xbadcafebee wrote: post #37
matheusmoreira wrote: post #22

Earlier quoted context omitted.

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…

> 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.

Re: The problem with reinforced concrete (2016)

#97

Post by dan-robertson »

Taek wrote: post #34
minikites wrote: post #4

Earlier quoted context omitted.

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

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).

Re: The problem with reinforced concrete (2016)

#98

Post by mortenjorck »

mc32 wrote: post #89
sesuximo wrote: post #10

Earlier quoted context omitted.

IMO yes; if the materials cost a lot of time/carbon/resources to produce, then we should make them last!

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

Re: The problem with reinforced concrete (2016)

#99

Post by raylad »

robocat wrote: post #73
raylad wrote: post #31

Earlier quoted context omitted.

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…

> 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…

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.

Re: The problem with reinforced concrete (2016)

#100

Post by quickthrowman »

mdgrech23 wrote: post #91
quickthrowman wrote: post #50

Earlier quoted context omitted.

> 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 proj…

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'…

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...

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