The problem with reinforced concrete (2016) • Hacker News Board

Re: The problem with reinforced concrete (2016)

#11

Post by Xamayon » Tue, May 25, 2021, 10:15 PM UTC

dmckeon wrote: post #2

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

That certainly helps, but in some cases such as when the rebar is under tension the epoxy coating can result in unexpected failure if there is any damage to it. The small areas lacking coating are corroded more aggressively, resulting in deep pitting which can weaken the bar to the point of failure.

Re: The problem with reinforced concrete (2016)

#12

Post by rsync » Tue, May 25, 2021, 10:16 PM UTC

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.

I don't believe you would encounter any red tape if you used hot-dipped galvanized rebar - I believe it is code-compliant everywhere in North America.

It is, however, more expensive ...

Re: The problem with reinforced concrete (2016)

#13

Post by rsync » Tue, May 25, 2021, 10:17 PM UTC

quickthrowman wrote: post #5

dmckeon wrote: post #2

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

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 ...

Re: The problem with reinforced concrete (2016)

#14

Post by autokad » Tue, May 25, 2021, 10:18 PM UTC

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!

I agree. Its like one of the few things we can give future generations. 'sorry about the debt, but heres some buildings'

Re: The problem with reinforced concrete (2016)

#15

Post by ska » Tue, May 25, 2021, 10:18 PM UTC

alcover wrote: post #9

There are also interesting new methods to monitor corrosion Then what ? Can you repair or replace parts of a building ?

They fairly regularly do localized repair on some structures (e.g. bridge/overpass).

Re: The problem with reinforced concrete (2016)

#16

Post by matheusmoreira » Tue, May 25, 2021, 10:19 PM UTC

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?

Re: The problem with reinforced concrete (2016)

#17

Post by brohee » Tue, May 25, 2021, 10:19 PM UTC

dmckeon wrote: post #2

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

It's pretty dependent on skilled people using it, every ding must be properly repainted before the concrete is poured, so extra care must be taken transporting and laying it.

https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galv... has a lot more, but clearly not a panacea...

Re: The problem with reinforced concrete (2016)

#18

Post by idoh » Tue, May 25, 2021, 10:20 PM UTC

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 reinforced concrete.

Re: The problem with reinforced concrete (2016)

#19

Post by tonylemesmer » Tue, May 25, 2021, 10:24 PM UTC

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...

Re: The problem with reinforced concrete (2016)

#20

Post by nerdponx » Tue, May 25, 2021, 10:25 PM UTC

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.