Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

smithsonianmag.com

Post reply on HN
Print view View original

41–50 of 236 posts

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#41

Post by joshellington »

There must be a better format and distribution method than this. Ideologically a strong brand name and domain, yet ads every two sentences. Even with ad blocking, there is constant aggressive attempts at attention.

I propose the communal brain rot is less to do with short form video, and more to do with the everyday experience of trying to read something enlightening, tickle your curiosity - and be just absolutely fucking hammered with autoplay interstitials and 720x90 and 300x250 bullshit.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#42

Post by somenameforme »

TylerE wrote: post #17
Mistletoe wrote: post #7

I’ve often wondered why every good sidewalk I see has a WPA stamp on it from the 1930s and the modern ones are all crumbled and uneven. https://share.gemini.google/5g0gxGyOmAPD

Survivorship bias in action.

I don't see how this would work because you're saying that the older sidewalks are scrapped and rebuilt when they hit a state of 'x' deterioration, so you only see > 'x' state ones. But how then could it be that newer sidewalks are allowed to fall below 'x' instead of also just being scrapped and rebuilt?

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#43

Post by wbl »

dev_l1x_be wrote: post #34
matheusmoreira wrote: post #28

Earlier quoted context omitted.

Nobody is going to tear down old bridges and rebuild them at enormous costs just because technology changed. Some things can't or won't be redone and so it's worth it to build it to last and getting it right on the first try.

This is exactly what we did with houses, buildings. We had perfectly functional 100+ years old fully functional, gorgeous buildings and we replaced those with brutalist concrete/glass barely functional garbage.

There are exactly 3 old buildings in Warsaw thanks to the Germans. Brutalism exists because a generation who grew up in rubble wanted solidity.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#44

Post by deepsun »

litoE wrote: post #20
bombela wrote: post #15

> It turns out that another chemical reaction, known as carbonation, might also contribute to Roman concrete’s longevity. Roman concrete was made lime cement (calcium dioxide); which cures via carbonation (hardens with carbon oxide). And adding pozzolan to lime makes it hydrolic (hardens with water). Is it surprising that it can still carbonate some? Modern concrete has steel which rust and crack concrete. You can us…

As I understand it, concrete has excellent resistance to compression but fails easily on traction, while steel bars are exactly the opposite. That is why you put rebar in concrete: the steel handles the traction loads and the concrete handles the compression. This works well because both materials have similar coefficients of thermal expansion, so as the temperature changes they both expand and contract at the same r…

> exactly the opposite

No, steel is better in both ways, ten times over. It's just more expensive, concrete is a "filler" to cheap out construction.

If you think about it, all engineering is about cheaping out things. It's pretty easy to build awesome projects having unlimited budget.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#45

Post by Alpha3031 »

userbinator wrote: post #14
demosthanos wrote: post #6

Related, Grady Hillhouse on the myth of Roman concrete. > The miracle of modern chemistry has given us a wide variety of admixtures like superplasticizers to improve the characteristics of concrete beyond a Roman engineer’s wildest dreams. So why does it seem that our concrete doesn’t last nearly as long as it should? It’s a complicated question, but one answer is economics. There’s a famous quote that says “Anyone c…

Most infrastructure is paid for by taxes, and the cost of building to Roman standards is rarely impossible, but often beyond what the public would consider reasonable. Would you pay 10x more to have something that lasts 100x or even 1000x longer? The upfront cost is higher, but the TCO is ultimately lower. IMHO it's ultimately a form of planned obsolescence. This becomes even more obvious when plenty of expense is sp…

No, because there are public projects that make sense at 3–4% discount rates that haven't been funded, so it would clearly make more sense to direct funding towards those projects first before trying to fund anything that requires a sub-1% discount rate.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#46

Post by hirako2000 »

joshellington wrote: post #41

There must be a better format and distribution method than this. Ideologically a strong brand name and domain, yet ads every two sentences. Even with ad blocking, there is constant aggressive attempts at attention. I propose the communal brain rot is less to do with short form video, and more to do with the everyday experience of trying to read something enlightening, tickle your curiosity - and be just absolutely fu…

Do you pay for satisfy your curiosity?

In fact, that institution is non profit and publicly funded, so what gives...

Anyhow reading the piece with Brave showed me no ads whatsoever.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#47

Post by altairprime »

somenameforme wrote: post #42
TylerE wrote: post #17

Earlier quoted context omitted.

Survivorship bias in action.

I don't see how this would work because you're saying that the older sidewalks are scrapped and rebuilt when they hit a state of 'x' deterioration, so you only see > 'x' state ones. But how then could it be that newer sidewalks are allowed to fall below 'x' instead of also just being scrapped and rebuilt?

Municipal budgets cratered hard over the past couple decades, roadway maintenance is given precedence over sidewalk maintenance, and SUVs and electric vehicles do considerably more roadway damage per vehicle. So there’s concurrent causes promoting a global decay in sidewalk maintenance in cities that expanded without the necessary tax base to support maintenance: see for example Los Angeles (current-day example!) repaving all but one foot’s width of their roadways so that they don’t have to fix broken sidewalks. This doesn’t contradict the survivor bias point! If anything, it’ll accelerate it: you’re about to see just how many (or few) sidewalk squares survive the underspend. Citizen science, here we come!

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#49

Post by hirako2000 »

TylerE wrote: post #16
userbinator wrote: post #14

Earlier quoted context omitted.

Most infrastructure is paid for by taxes, and the cost of building to Roman standards is rarely impossible, but often beyond what the public would consider reasonable. Would you pay 10x more to have something that lasts 100x or even 1000x longer? The upfront cost is higher, but the TCO is ultimately lower. IMHO it's ultimately a form of planned obsolescence. This becomes even more obvious when plenty of expense is sp…

The thing is, we're actually pretty crappy at knowing what we'll need 50 years from now, much less 500. Doesn't make sense to overbuild for an unknown future, when hundred years from now us will likely be able to do a far better job anyway.

That's to consider the commons solely materialist utility. The Romans built meaning through arts that still speaks to this day. Efficient construction becomes worthless over time.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#50

Post by pinkmuffinere »

litoE wrote: post #20
bombela wrote: post #15

> It turns out that another chemical reaction, known as carbonation, might also contribute to Roman concrete’s longevity. Roman concrete was made lime cement (calcium dioxide); which cures via carbonation (hardens with carbon oxide). And adding pozzolan to lime makes it hydrolic (hardens with water). Is it surprising that it can still carbonate some? Modern concrete has steel which rust and crack concrete. You can us…

As I understand it, concrete has excellent resistance to compression but fails easily on traction, while steel bars are exactly the opposite. That is why you put rebar in concrete: the steel handles the traction loads and the concrete handles the compression. This works well because both materials have similar coefficients of thermal expansion, so as the temperature changes they both expand and contract at the same r…

> Wouldn't your beams start cracking at the bottom, where they are subject to traction?

You have a few mistakes here. I’m not trying to demean you, but I’m going to number them just for clarity, as it can get confusing when there are many misunderstandings.

1. You are intending to ask about tension (which the rebar helps with), not traction (the force your tires exert against a road).

2. Tension is not only experienced at the bottom of beams, the location with the most tension will depend on the geometry. For a vertical beam, I think tension will probably be pretty even through the whole beam in most “normal” designs and loading configurations. But it will really depend on the geometry and on the loads being applied.

3. I think when you say concrete beams you’re meaning columns (apologies if I’m wrong about this). Concrete columns are remarkably good at holding up without rebar, because they experience almost exclusively compression! And indeed, ancient Roman designs did not use rebar at all :). It’s certainly possible.

Post reply on HN