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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#51

Post by lurquer »

minikites wrote: post #4
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…

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.

Re: The problem with reinforced concrete (2016)

#52

Post by redis_mlc »

chairmanwow1 wrote: post #8
dmckeon wrote: post #2

No mention of epoxy coatings for steel rebar? Look for green-coated rebar as you pass highway construction sites.

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…

That was a very entertaining video on rebar ... with 1.5 million views!

Curious what happened with those 4 bridges in VA with debonded epoxy.

Re: The problem with reinforced concrete (2016)

#53

Post by majormajor »

nerdponx wrote: post #20
idoh wrote: post #18

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 reinfor…

> 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.

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.

Re: The problem with reinforced concrete (2016)

#54

Post by jfoutz »

matheusmoreira wrote: post #22
ajcp wrote: post #21

Earlier quoted context omitted.

Yes.

Please elaborate. Which materials and methods?

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.

Re: The problem with reinforced concrete (2016)

#55

Post by redis_mlc »

rsync wrote: post #13
quickthrowman wrote: post #5

Earlier quoted context omitted.

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 ...

> stainless steel is a different material

First time in my life that somebody said that about stainless steel.

"On HN, our job is being pedantic."

Re: The problem with reinforced concrete (2016)

#56

Post by wonder_er »

GoToRO wrote: post #40
idoh wrote: post #18

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 reinfor…

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.

Re: The problem with reinforced concrete (2016)

#57

Post by tomatotomato37 »

XorNot wrote: post #27
Jerry2 wrote: post #24

Earlier quoted context omitted.

> 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 isn't persistent though - it burns.

In the context of building materials that's not a good thing

Re: The problem with reinforced concrete (2016)

#58

Post by teh_klev »

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 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.

Re: The problem with reinforced concrete (2016)

#59

Post by woah »

foolmeonce wrote: post #36
idoh wrote: post #18

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 reinfor…

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.

Huh?
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