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

Re: The problem with reinforced concrete (2016)

#131

Post by tomc1985 » Wed, May 26, 2021, 1:31 AM UTC

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…

Didn't they figure out that Roman concrete was made or infused with ash from a volcano or something?

https://en.wikipedia.org/wiki/Roman_concrete

Re: The problem with reinforced concrete (2016)

#132

Post by hdctambien » Wed, May 26, 2021, 1:35 AM UTC

quickthrowman wrote: post #100

mdgrech23 wrote: post #91

Earlier quoted context omitted.

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 caug…

Wasn't one of the problems with Boston's Big Dig that the contractors put an extra inch between bolts which saved them a ton of money (but ultimately killed a person)?

Re: The problem with reinforced concrete (2016)

#133

Post by mrfusion » Wed, May 26, 2021, 1:38 AM UTC

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 .

What are car mufflers made of that they resist rust so well?

Re: The problem with reinforced concrete (2016)

#134

Post by hdctambien » Wed, May 26, 2021, 1:40 AM UTC

culturestate wrote: post #125

WalterBright wrote: post #116

Earlier quoted context omitted.

I live in Rain City (Seattle). Quite a lot of homes are built with ridiculously tiny eaves. I'd never buy one of those. My house has eaves that stick out about 2 feet. It added nothing significant to the cost, but boy what a difference it makes. The exterior walls almost never get wet. The windows and their frames stay dry and free of rot. No mildew. Haven't even needed to repaint. There are a lot of things one can d…

There's nothing wrong with having long eaves if that's your preference; I'm just pointing out that there are a lot of factors that go in to building a long-lasting structure, and the answer to most questions around best practices is "it depends." If you have a two-storey house in a wet area that gets a lot of storm activity coming from the northeast, for example, and you have an exposed northeast-facing wall, the eav…

> might be good advice in Seattle, but if I told a local builder to worry about frost mitigation where I live now (Singapore) they'd probably question my sanity

Texas felt the same way until February!

Re: The problem with reinforced concrete (2016)

#135

Post by jaza » Wed, May 26, 2021, 1:46 AM UTC

throwawaysea wrote: post #23

An interesting read, albeit with information that is likely familiar to many. Given the issues surrounding concrete with greenhouse gases, recycling, and landfill contribution, it seems that timber ( https://arstechnica.com/information-technology/2012/05/wood-... ) may actually be a more viable alternative. We have techniques to grow it sustainably, it can be a carbon sink within a city, and it is mostly natural wood…

Yes, I've heard about engineered timber - https://blog.i1machines.com/four-reasons-why-engineered-timb... - I'm no expert, but it sounds like one of the better alternatives to reinforced concrete. Among its many benefits, it theoretically has a much longer lifespan than reinforced concrete.

I work right next to a seven-storey office building in Sydney, that's built almost entirely with engineered timber - https://architectureau.com/articles/australias-first-commerc... - ever bigger and taller such buildings are going up, bit by bit, around the world.

Re: The problem with reinforced concrete (2016)

#136

Post by culturestate » Wed, May 26, 2021, 1:49 AM UTC

hdctambien wrote: post #134

culturestate wrote: post #125

Earlier quoted context omitted.

There's nothing wrong with having long eaves if that's your preference; I'm just pointing out that there are a lot of factors that go in to building a long-lasting structure, and the answer to most questions around best practices is "it depends." If you have a two-storey house in a wet area that gets a lot of storm activity coming from the northeast, for example, and you have an exposed northeast-facing wall, the eav…

> might be good advice in Seattle, but if I told a local builder to worry about frost mitigation where I live now (Singapore) they'd probably question my sanity Texas felt the same way until February!

Singapore sits basically on the equator and the lowest recorded temperature ever was 66F, so if we somehow make it below freezing then something catastrophic has happened to the earth and plumbing would be the least of our problems.

Re: The problem with reinforced concrete (2016)

#137

Post by Dylan16807 » Wed, May 26, 2021, 1:49 AM UTC

hackeraccount wrote: post #45

nerdponx wrote: post #20

Earlier quoted context omitted.

> 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 bit like the one horse shay. It's not how long it lasts but what are the costs associated with it lasting any given length of time. Nothing lasts forever but say buildings lasted 500 years - Suddenly 500 years from now all buildings have to be replaced? And what's the cost of this 500 year building? Is it 10 times as much? Or is it 5 times as much? Saying we shouldn't have buildings that only last 50 years b…

> Suddenly 500 years from now all buildings have to be replaced? And what's the cost of this 500 year building? Is it 10 times as much? Or is it 5 times as much?

What a weird argument. It's obvious for multiple reasons that all buildings won't fail at the same time.

Re: The problem with reinforced concrete (2016)

#138

Post by thisisnico » Wed, May 26, 2021, 1:58 AM UTC

frosted-flakes wrote: post #82

phkahler wrote: post #77

Earlier quoted context omitted.

Knives tend to get washed.

And immediately dried.

My knives started showing some rust spots. I thought there must be something wrong with the knives, but I realized after googling, it was something wrong with how I was washing the knifes... I left it in a tub of very hot water and soap for a day, did this multiple times, viola, rust spots.

Re: The problem with reinforced concrete (2016)

#139

Post by oasisbob » Wed, May 26, 2021, 2:05 AM UTC

renewiltord wrote: post #108

jandrese wrote: post #103

Earlier quoted context omitted.

Although the hotels that hardwired RJ45 to each room are still going strong.

Right, they can stick APs in them. The point is that back then no one knew which tech would win and what tradeoff to make. Agility beats everything else except "guessing right".

For large institutions in the early 2000s, it was very obvious that Category 5 wiring and Ethernet was a difficult technology to beat. Even back then, most universities were running Ethernet to rooms in all new construction, and retrofitting spaces without it.

That infrastructure is still useful, 20 years on.

It isn't about agility or guessing right, it's about piloting attractive technologies (eg, small-scale DSL which uses existing phonelines, which was oftentimes a reliability nightmare), and keeping an eye to the future.

Re: The problem with reinforced concrete (2016)

#140

Post by naikrovek » Wed, May 26, 2021, 2:07 AM UTC

mrfusion wrote: post #133

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 .

What are car mufflers made of that they resist rust so well?

plain steel, I believe, but they get very hot on trips of even a few km, which drives off any resting moisture and prevents exhaust moisture from condensing for a while after the engine is stopped.

cars that make many short trips, which never give the exhaust system time to fully warm up, often have extremely compromised exhaust systems, because the moisture simply can't be driven away effectively.