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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

#101

Post by yorwba »

Animats wrote: post #54
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…

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…

> Two piers were built in the 1940s, side by side

As far as I can tell, only one pier was built (using stainless steel rebar) and the presentation is comparing it to a hypothetical alternative as a theoretical exercise: "What if the Progreso Pier was built using carbon steel rebar?"

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

#102

Post by _n_b_ »

ErroneousBosh wrote: post #56
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 costs much more, but total project cost goes up less than 10%. I think people are often surprised how little materials cost affects the total cost of a job. I'm having this argument at work, where I want some more expensive cabling installed in a bunch of offices across Scotland so it doesn't need to be done again in another ten year's time, but "that stuff is so expensive, do we really need it?" is…

I've worked on a few big EPC projects in a specialised industrial sector, including some in the UK. Three things drive the first digit of cost, assuming you've hired relatively competent engineers and constructors:

1. (Design) Building floorplate and architectural complexity (i.e., divergence from 'big box')

2. (Construction) Schedule adherence. Almost any one-off expense to stick to the schedule is worth it, but to your point, these are often challenged or delayed. Building and testing equipment on skids off-site is almost always worth it.

3. (Design/Commissioning) Schedule adherence. For commissioning this is typically driven by design choices (did you pick a high-TRL process, or if not, do all the work required to mature it in parallel to construction?) and by building the right commissioning team (knows their job, knows the plant).

If more expensive plant & equipment gets you ahead on any of these 3, 99% of the time that is an overall optimisation.

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

#103

Post by cm2187 »

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…

They could do large arches too, see https://en.wikipedia.org/wiki/Basilica_of_Maxentius

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

#104

Post by ErroneousBosh »

iamflimflam1 wrote: post #71
ErroneousBosh wrote: post #56

Earlier quoted context omitted.

> Stainless steel costs much more, but total project cost goes up less than 10%. I think people are often surprised how little materials cost affects the total cost of a job. I'm having this argument at work, where I want some more expensive cabling installed in a bunch of offices across Scotland so it doesn't need to be done again in another ten year's time, but "that stuff is so expensive, do we really need it?" is…

I hope you’re prepared for a huge amount of bike shedding… but if we pick this color, we can save a couple of dollars…

It's going in a suspended ceiling so it has to be purple.

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

#105

Post by ErroneousBosh »

PunchyHamster wrote: post #77
ErroneousBosh wrote: post #56

Earlier quoted context omitted.

> Stainless steel costs much more, but total project cost goes up less than 10%. I think people are often surprised how little materials cost affects the total cost of a job. I'm having this argument at work, where I want some more expensive cabling installed in a bunch of offices across Scotland so it doesn't need to be done again in another ten year's time, but "that stuff is so expensive, do we really need it?" is…

> I think people are often surprised how little materials cost affects the total cost of a job. It's because they frankly never did it. Nobody that had to contract something around the house is surprised by cost like that, it often costs more than price of renting equipment + you doing it yourself 3 times slower than an expert would did it, even if you're paid well. There is reason there is so many DIY channels, labo…

Yeah. I mean I just had some concrete slabs laid to put a bike shed on (literally bikeshedding, the colour is green, that's what it comes powdercoated in from the supplier, take it or leave it).

It was 300 quid.

I could not buy the materials for 300 quid.

Two guys showed up with eight slabs, half a tonne of Type 2 and half a tonne of sand, and then the next day the landscaper showed up and did about six hours of work to dig it all out, fill it all in, and put the slabs down.

It's absolutely perfect, exactly how I wanted it, and it would have taken me a couple of days and cost far more - and I'm quite good at that kind of stuff, it's just not what I do all day every day so the landscaper will be far better at it.

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

#106

Post by lazide »

amszmidt wrote: post #100
meindnoch wrote: post #97

Earlier quoted context omitted.

>Cement/Concrete (based on Portland cement) is water proof That's patently untrue. Otherwise we wouldn't need concrete sealants.

The key here is “based on Portland cement”, which is generally has water repellent added to it making it water proof. Normal cement, concrete .. Is a different story.

Concrete is generally porous and definitely not micro-waterproof (aka lots of water vapor makes it’s way through). Including if using Portland cement.

It is generally macro-waterproof, however, unless there are large cracks.

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

#107

Post by GuB-42 »

cm2187 wrote: post #78

I am glad the pantheon still stands. But the real question is are there really any modern structure that will be worth preserving for 2000 years. Architects have long abandoned aiming for beauty to aim for originality. Originality doesn’t last. Humans in 2000 years will only wonder why on earth our society could manufacture atom level micro ships but couldn’t come with a single structure worth preserving.

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 much better fits the classical standards of beauty.

The Eiffel tower is also more historically significant, more representative of its time. The Paris Pantheon, is an imitation of the Roman style, beautiful, but probably not as interesting for future historians. If both building survive that is, which won't happen without continuous maintenance, at least for the Eiffel tower.

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

#108

Post by masklinn »

terribleperson wrote: post #22
masklinn wrote: post #10

Earlier quoted context omitted.

> Stainless steel rebar could be used There are also coated and non-metallic rebars.

Coated rebar could be good, but the coating can be damaged anywhere from manufacture to installation.

Yup, every alternative rebar has drawbacks which causes increased costs or different failure modes which is why they tend to be used in specialised applications where they are necessary.

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

#109

Post by GuB-42 »

Saline9515 wrote: post #96
cm2187 wrote: post #78

I am glad the pantheon still stands. But the real question is are there really any modern structure that will be worth preserving for 2000 years. Architects have long abandoned aiming for beauty to aim for originality. Originality doesn’t last. Humans in 2000 years will only wonder why on earth our society could manufacture atom level micro ships but couldn’t come with a single structure worth preserving.

Sand used to make concrete is a finite ressource, and extremely polluting to extract. Why wouldn't we save it and build lasting buildings?

It is not.

You can make sand by crushing rock, we don't because it is cheaper to extract natural sand. Should we run out of suitable natural sand, we will just have to go with the more expensive option, not a big deal.

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

#110

Post by hirako2000 »

TylerE wrote: post #62
hirako2000 wrote: post #49

Earlier quoted context omitted.

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.

The kind of efficiency we focus on seem to be plentiful. Labour is a good example, see unemployment rates and the number of bullshit jobs anyway.

What's covered in the article is also a great example of material resource that could be used, but short term profiting primes.

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