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

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

#61

Post by selcuka »

deepsun wrote: post #44
litoE wrote: post #20

Earlier quoted context omitted.

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.

As one of my professors said back in time: "Steel is one of the best materials for a number of applications. We don't use it only because it's abundant. "Abundant" and "good" are not always mutually exclusive."

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

#62

Post by TylerE »

hirako2000 wrote: post #49
TylerE wrote: post #16

Earlier quoted context omitted.

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.

Efficiency is never worthless in a world where resources (if nothing else, labor) are not infinite.

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

#63

Post by culi »

aiauthoritydev wrote: post #24

The whole promise of engineering is not to build a bridge that stands but to build a bridge that barely stands. It is not a good idea to build a bridge that last 500 years. You likely destroyed valuable resources to build one. Build a bridge that lasts 100 years and save those resources. In 100 years the technology to build bridges improves so much that it is lot easier to build a new one. At least in most countries…

Modern concrete includes plastic fibers like polypropylene, fly ash (a great source of arsenic, lead, and mercury), silica fume, formaldehyde, and often even PFAS

This type of concrete does not give us any more flexibility in the future to rebuild or upgrade because doing anything to it could turn it into an environmental and public health hazard

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

#64

Post by golem14 »

Aurornis wrote: post #25
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…

No, for two reasons. First, we can’t summon infinite money to pay for things. Paying 10X more per bridge means we can build 1/10th as many bridges or we have to start stealing from other budgets. Second, we don’t know what the needs will be for the bridge in that location 100 or 1000 years from now. It could need to be torn down to be widened. Maybe we’re all riding around in electric vehicles that coordinate perfect…

Well, invading a few fewer countries could pay for a few longer lasting bridges … it’s a matter of priorities.

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

#65

Post by culi »

croes wrote: post #32
aiauthoritydev wrote: post #24

The whole promise of engineering is not to build a bridge that stands but to build a bridge that barely stands. It is not a good idea to build a bridge that last 500 years. You likely destroyed valuable resources to build one. Build a bridge that lasts 100 years and save those resources. In 100 years the technology to build bridges improves so much that it is lot easier to build a new one. At least in most countries…

Sometimes knowledge gets lost and newer doesn’t automatically mean better

In fact, the dominance of concrete is surprisingly political. It has a lot to do with Cold War geopolitics

https://www.listennotes.com/podcasts/the-conversation/keepin...

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

#66

Post by eru »

Barbing wrote: post #23
eru wrote: post #8

Earlier quoted context omitted.

Yes, but you have to replace the sacrificial anode every so often. https://en.wikipedia.org/wiki/Galvanic_anode

Like the plate of food on the grass for the bees at the barbecue

More for the wasps, I guess?

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

#67

Post by somenameforme »

Cthulhu_ wrote: post #59
somenameforme wrote: post #42

Earlier quoted context omitted.

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?

Politics, money allocation, taxation, etc. The US had a golden age last century and is now in decline. It can still bounce back but it needs a political and legal revolution, in this particular case, it needs to tax the wealthy and spend it on municipal improvements. But that's socialism / liberalism and apparently that's terrorism now.

This is a bit of a tangent, but government revenue has skyrocketed in recent decades. Here is an inflation adjusted table. [1] As a percent of GDP it's been fairly stable since the end of WW2 [2], and dramatically higher than prior. But that understates reality because it excludes deficit spending which has increased exponentially since then. So the government is collecting and spending substantially more than back in the golden age, even after accounting for population/economic/etc growth.

[1] - https://usafacts.org/answers/how-much-does-the-us-federal-go...

[2] - https://fred.stlouisfed.org/series/FYFRGDA188S

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

#68

Post by Izmaki »

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…

> but that is more costly and and less efficient.

Maybe this is the clue as to why our concrete crumbles after 100 years: it's not economically efficient to make it last longer?

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

#69

Post by aYsY4dDQ2NrcNzA »

Izmaki wrote: post #68
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…

> but that is more costly and and less efficient. Maybe this is the clue as to why our concrete crumbles after 100 years: it's not economically efficient to make it last longer?

I’m passing my latrine down to our great grandchildren.

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

#70

Post by anal_reactor »

modo_mario wrote: post #60
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…

The same is said for why we don't build classical buildings anymore and trend towards more featureless stuff... and it's also mostly bullshit with plenty of counterexamples. Truth is it's often just a bit cheaper so we trend that way under capitalism, we change styles faster and have come to subconsciously accept shorter lifespans and the kind of things you can build more practical for cars, large overhangs, etc

But it's also true that modern world changes much faster than in the antiquity. If you built a church, a market, and a few utility buildings like tavern and blacksmith in 500BC you could rest assured they'd still remain used in 1000 years practically unchanged unless the structure or wider economy collapsed. Meanwhile "office building, shopping mall, nightclub, school" all varied highly in popularity within last 50 years, and it's difficult to convert one type of building to another, not to mention the costs of modernizing an old building.
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