291–299 of 299 posts
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Can't confirm. Drive unsafely like the worst drivers in LA and you'll fit right in but still be miserable.
Hah. Probably practice is needed, but your holidays are too short for that.
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Not always, if rebars are pre-tensioned before concrete solidifies. So the rebar is always under tension. Pretty common in prefab parts, like bridge bars.
For someone totally outside this space I had assumed concrete is rigid and brittle and rebar reinforcement allows for it to bend and flex without breaking. But your comment makes it feel like it keeps the concrete in tension with compression forces to make it sturdier. Can you ELI5 what the rebar does to help?
The rebar handles tensile loads, the concrete handles compressive loads. You put the rebar where tension will exist so that it can handle that. Some amount of cracking on non-pretensioned concrete is normal and unavoidable.
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>There is also reinforced concrete, which the Romans didn't have. While concrete by itself can in principle be moulded into any shape, this can sometimes fall apart, even after hardening. Reinforcement refers to putting a concrete around metal wiring, providing more versatility. Not a correction per se, but some further explanation. The reason for reinforcement is because concrete is strong in compression and weak in…
There's a small trend towards stainless steel rebar. It's expensive, but is now used for concrete structures near salt water. Epoxy coated rebar turned out to be a mistake. One scrape in the epoxy and it starts rusting. Exposure to UV prior to installation can damage the epoxy coating. Currently banned in Quebec.[1] [1] https://news.ycombinator.com/item?id=27676447
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Hah. Probably practice is needed, but your holidays are too short for that.
There's objective aspects of safe driving like leaving enough distance between vehicles (depending on speed) that are wildly ignored. You might get used to that in practice but that doesn't make it safer.
I was not thinking about excessive speeds or tailgating.
In Southern Italy, when you are stuck in a traffic jam in the city, you just drive nearer to other cars, and this is only mildly dangerous because you don't have high speeds.
If you don't drive tight enough, you just can't proceed because some other car will take your place.
This is not tailgating or driving recklessly.
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There's objective aspects of safe driving like leaving enough distance between vehicles (depending on speed) that are wildly ignored. You might get used to that in practice but that doesn't make it safer.
I was thinking about chaotic Italian road crossings. Or, to give another example, l'Arc de Triomphe in Paris. People tend to communicate with their cars where they want to drive and I understand that foreigners find this aggressive. I was not thinking about excessive speeds or tailgating. In Southern Italy, when you are stuck in a traffic jam in the city, you just drive nearer to other cars, and this is only mildly d…
Lots of crosses remembering dead drivers on the side of the roads too.
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Being literate definitely means some faculties get less practice. Practically nobody today can recite epic poetry like the Odyssey, for example. That lack of rote memorization skill may have unexpected side-effects. https://daily.jstor.org/how-do-we-know-that-epic-poems-were-...
Thats a really good, succinct, statement that triggers thought - where ironically - being literate is required to reply to via the most advanced machine I have ever used... But there are so many skills lost due to the privilege of technologically enabled sedentary life-styles... can you imagine attemting to found a town/village/city in flat/cold/resource-constrained climates without electricity/supply-lines? Those pe…
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The rust is essential to bind it to the cement. Without, it adds little strength. Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone. We have a…
> The rust is essential to bind it to the cement What? This is total nonsense. > Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Is hacker news a conspiracy theory website now? > We have a very great deal of infrastructure that will fail on a predictable schedule Wood rots in a few years under certain co…
Here is a nice picture of the Pantheon, mentioned in the article as a prime example of these incredibly durable Roman concrete structures: https://commons.wikimedia.org/wiki/File:Pantheon11111.jpg#/m... Not bad for something built nearly 2,000 years ago.
Uses pumice in aggregate as aerated mass to lighten the concrete and also varies concrete thickness by height in the dome to reduce load
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Well, I lived in Italy for 10 years. Going to Rome from time to time wasn't that hard. Now I live in Spain and I continue to fly to Rome now and then. In Europe, distances are easy to overcome.
In Europe, 100km is a long way; in the US, 100 years is a long time.