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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

#91

Post by aaron695 »

iknownothow wrote: post #75
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…

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.

[dead]

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

#92

Post by Saline9515 »

aYsY4dDQ2NrcNzA wrote: post #69
Izmaki wrote: post #68

Earlier quoted context omitted.

> 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.

You don't really own a latrine, but just look for it for the next generation.

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

#93

Post by benj111 »

ascorbic wrote: post #38
dev_l1x_be wrote: post #34

Earlier quoted context omitted.

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.

They weren't torn down because there was better technology available. They were torn down because they were falling apart, or were no longer meeting the needs in that location. I love old buildings – my house is 250 years old – but there's no denying that generally they are less suited to current needs than newer buildings.

Older buildings are generally more flexible though.

In the UK, within living memory electricity has become widely available, TV has, gas, internet etc etc. and yet we still build houses without the assumption that some cable isn't going to be modified in the wall some how.

There's fairly modern houses that didnt have the 2 courses of brick added to the loft to allow 300mm of insulation to be installed.

We are now building houses with gas boilers, knowing that they will have to be swapped out probably before the life of the boiler runs out. And I bet the radiators and piping aren't sized to make that possible. That the circuit isn't sized for that.

Yes none of this is easier in a 250 year old house, but it isn't harder and 250 year old houses hadn't really changed appreciably for a few centuries so it isn't as if there would be an expectation that you would be installing new things in the wall every decade.

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

#94

Post by carlmr »

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?

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

#95

Post by Hugsbox »

throwaway27448 wrote: post #31
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…

> In 100 years the technology to build bridges improves so much that it is lot easier to build a new one This hasn't even been true for 200 years lol

We don't build better bridges than we did 200 years ago? Forgive me if I'm wrong, but it seems like we build bridges right now that would have been unthinkable 200 years ago

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

#96

Post by Saline9515 »

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?

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

#97

Post by meindnoch »

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…

>Cement/Concrete (based on Portland cement) is water proof

That's patently untrue. Otherwise we wouldn't need concrete sealants.

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

#98

Post by _n_b_ »

iknownothow wrote: post #75
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…

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.

> Lime takes a while to set (a few days?)

Up to 30 days to set, and depending on the type of lime (hydraulic or non-hydraulic) and form/process (putty, hot mix, etc.) up to a year to reach full hardness.

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

#99

Post by ajwin »

A lot of the reason why concrete structures have failed so quickly is that the material was still fairly new when most of the structures failing now were created. There’s nothing that says that well designed and constructed modern high performance polymer modified concretes will have the same problems. They also have additives like zypex paste that make it more waterproof and self healing. They also have permeable formwork liners for increasing the surface density of the concrete and chemical concrete hardeners etc.

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

#100

Post by amszmidt »

meindnoch wrote: post #97
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…

>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.

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