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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#81

Post by kortex »

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…

There's also basalt fiber reinforced concrete. Stronger than rebar and doesn't rust.

Re: The problem with reinforced concrete (2016)

#83

Post by gamblor956 »

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 version of Roman cement."

Re: The problem with reinforced concrete (2016)

#84

Post by singlow »

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…

But on big projects, doesn't the architect often work for the bidder?

Re: The problem with reinforced concrete (2016)

#85

Post by WalterBright »

matheusmoreira wrote: post #16
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…

How can I know if a building was designed to last a long time? Is it the materials, the method of construction?

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.

Re: The problem with reinforced concrete (2016)

#86

Post by lmilcin »

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

Re: The problem with reinforced concrete (2016)

#87

Post by nickff »

autokad wrote: post #14
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!

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.

Re: The problem with reinforced concrete (2016)

#88

Post by quickthrowman »

singlow wrote: post #84
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…

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.

Re: The problem with reinforced concrete (2016)

#89

Post by mc32 »

sesuximo wrote: post #10
minikites wrote: post #4

Earlier quoted context omitted.

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!

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.

Re: The problem with reinforced concrete (2016)

#90

Post by kortex »

Jerry2 wrote: post #24
tonylemesmer wrote: post #19

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...

> 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/

> 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.

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