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Why Ancient Roman Concrete Outlasts Our Own (2017)

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Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#11

Post by hef19898 »

eru wrote: post #9
Phithagoras wrote: post #2

In a second year class I took the prof posed us the question: why don't we do this today? Why is this not part of an ASTM standard? He ended up saying it's too tough to get a hold of proper pozzlanic ash, but I suspect its more a "this is the way we've always done it" difficulty. Does anyone know more to the story?

First, we only see the part of Roman architecture that lasted. There's an observer bias. The Romans also made plenty of ephemeral stuff, just like we are making plenty of ephemeral stuff. See also https://www.youtube.com/watch?v=qL0BB2PRY7k Second, there's more to engineering than making stuff last long. There are different trade-offs. Cost being one of them, but also different material properties. Eg re-inforced con…

Trade offs should be covered a lot more during engineering studies. I know that during my time at university, as an industrial engineer destined to work at the interface engineering and economics, that aspect wasn't covered nearly as extensive as it should have. The other question that usually get's ignored is maintenance. The Roman stuff we see lasted millennia without maintenance, we on the other hand can maintain the stuff we want to last a long time.

That we don't do it, e.g. infrastructure with the particularly bad maintained bridges in Germany, is not the materials fault, or the original designs fault.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#12

Post by jacquesm »

leroman wrote: post #3
Phithagoras wrote: post #2

In a second year class I took the prof posed us the question: why don't we do this today? Why is this not part of an ASTM standard? He ended up saying it's too tough to get a hold of proper pozzlanic ash, but I suspect its more a "this is the way we've always done it" difficulty. Does anyone know more to the story?

Maybe industries “planned obsolescence” practice?

I think designing your buildings for more than a few hundred year counts as 'excessive' and more than 250 years should not allow for being disqualified under 'planned obsolescence'.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#13

Post by jacquesm »

eru wrote: post #10
xyzzyz wrote: post #8

Earlier quoted context omitted.

Yes, and these factories are many, and are not concentrated in one place, because shipping cement is expensive. It’s the same with aggregate: not everyone has sand in their backyard, but there typically is good amount of suitable sand within a few dozen miles.

It's even more interesting that than! There's actually plenty of drama around sand for concrete. There's talks about 'sand mafias' in India. And Malaysia has banned exporting sand to Singapore. See eg https://www.bbc.com/future/article/20191108-why-the-world-is...

Similar stuff has happened in Germany, in fairly recent times. You could make your own cement, no problem. But good luck trying to unload it anywhere in Germany without paying a fee to certain individuals.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#14

Post by jbay808 »

eru wrote: post #9
Phithagoras wrote: post #2

In a second year class I took the prof posed us the question: why don't we do this today? Why is this not part of an ASTM standard? He ended up saying it's too tough to get a hold of proper pozzlanic ash, but I suspect its more a "this is the way we've always done it" difficulty. Does anyone know more to the story?

First, we only see the part of Roman architecture that lasted. There's an observer bias. The Romans also made plenty of ephemeral stuff, just like we are making plenty of ephemeral stuff. See also https://www.youtube.com/watch?v=qL0BB2PRY7k Second, there's more to engineering than making stuff last long. There are different trade-offs. Cost being one of them, but also different material properties. Eg re-inforced con…

Are you essentially saying that you don't think there are important material and chemical differences between Roman and modern concrete that might be responsible for orders-of-magnitude differences in durability, aside from the absence of rebar, and that it's basically a matter of building so many bridges, harbours, and aqueducts that some of them end up lasting for thousands of years despite being immersed in running rivers or salt water?

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#17

Post by Eelongate »

jbay808 wrote: post #14
eru wrote: post #9

Earlier quoted context omitted.

First, we only see the part of Roman architecture that lasted. There's an observer bias. The Romans also made plenty of ephemeral stuff, just like we are making plenty of ephemeral stuff. See also https://www.youtube.com/watch?v=qL0BB2PRY7k Second, there's more to engineering than making stuff last long. There are different trade-offs. Cost being one of them, but also different material properties. Eg re-inforced con…

Are you essentially saying that you don't think there are important material and chemical differences between Roman and modern concrete that might be responsible for orders-of-magnitude differences in durability, aside from the absence of rebar, and that it's basically a matter of building so many bridges, harbours, and aqueducts that some of them end up lasting for thousands of years despite being immersed in runnin…

Absence of rebar is a huge difference. From what I understand it's the primary reason most modern concrete structures are expected to last only on the order of decades to a century or two. Some modern structures have been built without much if any rebar, for instance the Hoover Dam, and I've heard that might last thousands of years.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#18

Post by smt88 »

leroman wrote: post #3
Phithagoras wrote: post #2

In a second year class I took the prof posed us the question: why don't we do this today? Why is this not part of an ASTM standard? He ended up saying it's too tough to get a hold of proper pozzlanic ash, but I suspect its more a "this is the way we've always done it" difficulty. Does anyone know more to the story?

Maybe industries “planned obsolescence” practice?

No. An industry does not make a plan 50+ years in advance to get more business.

They do, however, save on costs by delivering products that don't last as long because their customers also don't (as a general rule) care about 50+ year time horizons.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#19

Post by TeeMassive »

eru wrote: post #9
Phithagoras wrote: post #2

In a second year class I took the prof posed us the question: why don't we do this today? Why is this not part of an ASTM standard? He ended up saying it's too tough to get a hold of proper pozzlanic ash, but I suspect its more a "this is the way we've always done it" difficulty. Does anyone know more to the story?

First, we only see the part of Roman architecture that lasted. There's an observer bias. The Romans also made plenty of ephemeral stuff, just like we are making plenty of ephemeral stuff. See also https://www.youtube.com/watch?v=qL0BB2PRY7k Second, there's more to engineering than making stuff last long. There are different trade-offs. Cost being one of them, but also different material properties. Eg re-inforced con…

Not to mention that concrete steel reinforcement is the main reason it doesn't last due to water eventually making its way and the rust taking expansion thus cracking the concrete.

Re: Why Ancient Roman Concrete Outlasts Our Own (2017)

#20

Post by smt88 »

14 wrote: post #5
leroman wrote: post #3

Earlier quoted context omitted.

Maybe industries “planned obsolescence” practice?

But surely some company would see it as an advantage over competitors and sell it if it was easily accessible. But we don’t see that so there has to be more to it. Maybe cost is too high for the average customer?

> But surely some company would see it as an advantage over competitors and sell it if it was easily accessible.

This is not a guarantee. Look at manufacturers of washing machines: every company makes more money by having unreliable machines. There is no financial incentive to build a better product, and it's not easy to even prove you've built a better product.

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