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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

#141

Post by freedomben »

rkangel wrote: post #82
PunchyHamster wrote: post #79

Earlier quoted context omitted.

Or simpler: people don't exactly want a house layout that was popular 100 years ago. And definitely not the level of insulation it provided. Nor the fact putting any new wiring and piping thru concrete is PITA Tastes change and so do other requirements. but , if we actually built for longevity in use, we could build a very durable shell of a house and then use more perishable but easier to modify methods for inside.…

There are some downsides, but most people on the UK would prefer houses that were 100+ years old. In the village I live in the houses immediately around me are "only" 50 years old. Most of the ones on the main street are well over 100 years old. Housing tastes don't really change that much. Yes over the years we've had to fit things like double glazing and better insulation but that's a whole lot cheaper (and better…

> but most people on the UK would prefer houses that were 100+ years old.

Why do most people prefer older houses?

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

#142

Post by throw0101d »

mikepurvis wrote: post #26
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…

To build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere. But it turns out that's pretty inconvenient; we really like doing dozens of feet of span for highway overpasses, building floors, and everything else. So we put rebar in all the concrete and just acknowled…

> To build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere.

Until an earthquake occurs, and then all of those mostly-down forces turn into side-to-side forces.

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

#143

Post by eru »

jaapz wrote: post #127
Barbing wrote: post #23

Earlier quoted context omitted.

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

Wait, does this actually work?

It sure attracts the wasps. Whether you have less of them on your real food compared to the counterfactual, I don't know.

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

#144

Post by IAmBroom »

carlmr wrote: post #94
iknownothow wrote: post #74

For those not familiar, the secret ingredients are to do with the Lime Cycle [1]: 1) Quicklime/Slakedlime (Calcium Oxide, CaO) 2) Lime (Calcium Hydroxide, CaOH2) 3) Limestone (Calcium Carbonate, CaCO3) To keep it simple, typically you start with Quicklime (CaO) and after construction you end up with some mix of all three and after hundreds of years, the masonry transitions to mostly Limestone with microscopic traces…

>Fun fact! Lime putty is anti-mold even in humid conditions because upon exposure to moisture, CaOH2 + H20 becomes too basic for mold to grow on. Can we use this instead of grout in the bathroom somehow?

Pure silicone caulk is mold-proof, even in the white variation. The various "improvements" in many caulks allow mold to get a foothold.

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

#145

Post by IAmBroom »

dnemmers wrote: post #121
iknownothow wrote: post #75

Earlier quoted context omitted.

I forgot another important reason why Portland cement is preferred over lime these days. Lime takes a while to set (a few days?), cement sets faster.

Cement will still take many days to reach full cure time (measured in increasing PSI ratings) https://www.ce.memphis.edu/1101/notes/concrete/section_3_pro...

You aren't contradicting anything. MOST of the strength is achieved in 24 hours or less.

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

#146

Post by IAmBroom »

throw0101d wrote: post #139
Animats wrote: post #54

Earlier quoted context omitted.

Stainless steel rebar is a thing. It's expensive, but structures built with it last much longer. Washington State now has a policy that bridges over salt water will be built with stainless steel rebar. Stainless steel costs much more, but total project cost goes up less than 10%. Epoxy coated rebar looked promising for a while, but it's on the way out. Water gets in at cuts and joints. So all field joints have to hav…

> Stainless steel rebar is a thing. It's expensive […] That's an understatement. Fiberglass (GFRP) tops out at roughly US$ 2.50/foot, while SS can get up to $9: * https://www.wellcoindustries.com/the-cost-of-rebar-and-the-c... The low-end of plain steel rebar is $0.40.

As the GP noted, it's still only a small bump in overall cost.

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

#147

Post by rewtraw »

we can't figure out roman concrete

we don't know how ancient megaliths were built

centuries old cathedrals and holy places have more intricate masonry and carvings than anything built today (with allegedly more primitive tech)

are historians retarded? what's going on here? time is flowing backwards and civilization is declining, but humanity is under a collective trance and can't even see it.

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

#148

Post by projektfu »

kergonath wrote: post #53
pinkmuffinere wrote: post #50

Earlier quoted context omitted.

> 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 experienc…

> 1. You are intending to ask about tension (which the rebar helps with), not traction (the force your tires exert against a road). I don’t know if it is the case here, but it is a common mistake for some non-native English speakers. In some languages traction is a false friend.

And in English, traction also means pulling, but it got somewhat misapplied to the friction of tires, causing confusion in the language. For example, a tractor is something that pulls, and when a broken leg is put in traction, it's suspended to pull it apart and keep the muscles from pulling it together.

Tension, as you say, is indeed the term used in physics and engineering for the force on an object pulling it from either end.

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

#149

Post by smalltorch »

skybrian wrote: post #2

Modern concrete has steel rebar, which is very useful, but eventually corrodes. Stainless steel rebar could be used if longevity mattered, but usually it doesn’t because the building will likely become functionally obsolete and need replacing before then.

It only corrodes if it's not completely encased in concrete. The concrete stops the reaction. And, if one portion of the rebar is not encased it will eventually corrode through overtime.

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

#150

Post by GuB-42 »

cm2187 wrote: post #125
GuB-42 wrote: post #107

Earlier quoted context omitted.

All structures are worth preserving. The article is about a latrine. Do you think ancient Romans thought a literal shithole was worth preserving? And yet, it is now an important piece of history. As for beauty, you never know, take the Eiffel tower for instance, when it was built, people found it ugly, and it was to be a temporary structure. Now it is the symbol of Paris, more popular than the Paris Pantheon, which m…

The Eiffel Tower dates from the XIX century. Pre the shift to originality. Which XX century building in Paris is objectively beautiful? The tour Montparnasse? The Centre Pompidou? Or Jussieu’s campus? Even the Opera Bastille is pretty lame, not outright ugly but lame.

I like Centre Pompidou, and if it wasn't technically problematic, it could have aged really well.

For those who don't know, Centre Pompidou is built "inside out", with all the technical parts like ducts, framing, elevators, etc... fully visible from the outside. There is some beauty from function here, like looking at an old locomotive. For people in the future, it would be an insight into what a 20th century building is made of.

Problem is: for a form-from-function design it is not very functional. Because the technical parts are also part of the aesthetics, it makes maintenance problematic. Every single pipe you change has to be of the same model or you would ruin the façade, which is crazy. Unfortunately (for me), it is one of the least likely building to stand the test of time, from a technical perspective.

Other than that, the Louvres pyramid is starting to gain some acceptance, even though it was almost universally hated when it was built, who knows how it will be seen a few hundred years from now, if it still stands.

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