Mystery of Roman Concrete Durability Solved...or so they say 2

[phamENG]

Looks like a big study out of MIT was published last week regarding durability in Roman Concrete. Seems it was designed to be self healing, using quicklime inclusions to create deposits of CaO that could react with water flowing through cracks to fill the cracks with calcite. Pretty neat.

Here's an article summarizing it: Link

If you're more adventurous, here's the paper: Link

Says they're looking to commercialize it. I wonder what the copyright patent law says about 2000 year old technology...feels like it might be in the public domain by now...

 

[Teguci]

First, very interesting - well worth the read

Here are some skeptical thoughts:
- Is Roman concrete superior because of the mix design or we assume that because only the best of their concrete is what survives? (cherry picking)
- Many can overdesign a wall, arch, pyramid. It takes an engineer to design it close to failure.
- Current mass concrete design is focused on dispersing heat to avoid large thermal volume change. Is this self healing preferred over internal thermal cracking due to "hot mixing"? This could change dam design.
- Since the lime clasts are what heals cracks, do the cracks form near lime clasts because they weaken the concrete? (this is indicated in the report)
- When it comes to archeology, I think "Motel of the Mysteries" is accurate.

 

[IRstuff]

Note that copyright pertains to printed material; this would be subject to patent laws, but any patent would have expired by now. Any new patent can be challenged, since it's obviously "prior art," which is not patentable, particularly if they got the formula exactly the same. They would need to make some sort of improvement to get a patent.

thread1088-501310 previous discussion about the concrete itself.


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[phamENG]

Thanks, IR - you're right about it being a patent. Fixed my OP.

 

[1503-44]

Took these pics in Nov, ... after 1950 some years.
They have installed some tension rods though. Maybe they were a bit short on lime.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[rb1957]

that is in spain yes ? I was at pont du gard some years back (had my car broken into, in Arles !)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[1503-44]

It happens. But you will probably not get hurt. Segovia is small and pretty safe. They have a huge parking garage with controlled access. Barcelona is the worst place these days.

I have not been to Arles. I wouldn't mind having a a visit there.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[centondollar]

Maybe I'm being pessimistic, but I don't see much commercial use for such concrete, since its durability is contingent on not using steel reinforcement. Nearly all useful concrete structures require reinforcement. Reinforcement rusts (not if, but when) and eventually destroys the structure from within (spalling, volume increase which causes chunks of concrete of fall off etc.) with fatigue and serviceability issues being the final kicker. Deep shells (not common in construction) or columns without bending (also not common in construction) or non-structural blinding concrete (which can be very durable even with off-the-shelf mix designs) are the application areas that directly come to mind.

 

[canwesteng]

Yeah, even 20th century concrete can last an exceptionally long time, but the amount of concrete used to keep it from needing rebar for flexure is pretty substantial. And then you wonder what the point is - my hometown had 100+ year old bridge with I believe plain concrete piers, that were in great shape, but they knocked it down anyway since the steel above it was falling apart and it was too narrow for cars.

 

[IRstuff]

The Hoover Dam's concrete is mostly metal-free, although they embedded steel pipes to cool the concrete during curing. Would be interesting to see how well the steel held up, compared to rebar. Of note, the dam's concrete is ostensibly rebar-free. It's supposedly designed to survive into the foreseeable future

https://www.usbr.gov/lc/hooverdam/history/essays/concrete.html

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[1503-44]

It may be interesting for use in various structures that essentially only provide weight and friction restraint. Offshore gravity stabilized platforms comes to mind (once a thing, although not used much these days) as does large diameter pipeline anchors, guyed tower cable anchors, embeddment grouts, or dock and warf type structures? Things that have little tension, but you don't want them cracking up anytime soon.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[phamENG]

1503-44 - I think you're right. There is a narrow use set for these but it does exist.

Barring some significant breakthroughs in structural technology that utilize shells and arches that gains widespread acceptance OR a complete rethinking of modern architectural aesthetics, these will be relegated to existing gravity type structures. (I post that link to point to somebody trying...probably not usable with this kind of concrete as the inclusions may compromise the fine rib structures in the panel.)

Teguci - cherry picking is usually my argument for the whole 'they don't build them like they used to' argument I get from a lot of contractors and homeowners. But I'm not certain here. It could be that these are simply exceptional examples, but to stand for 2 millennia...they are exceptional indeed. I find it hard to believe that the 'average' was that inferior. Of course it could be, though.

canwesteng - that does bring up an interesting discussion at the border of engineering and public policy. Here in the states, most of us driving on the roads would love to have to demolish a bridge when we're done with it, rather than have the bridge tell us that it's time to be demolished. So perhaps the question is just that: do we want to dictate the evolution of our infrastructure, or do we want decay and deterioration to dictate it? There are arguments for both, but I think land in the camp of the former so long as the cost isn't so grossly unpalatable as to make it impossible to fund.

 

[rb1957]

do you mean the Romans didn't need/use steel reinforcement ?? Further evidence of their superiority !

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[1503-44]

The medieval cathedral builders had the same problem with tension and they didn't even have Roman concrete. The flying buttresses were all about providing lateral bracing to the main structure with arches, using the little pinicles to supply extra weight where needed to keep the arches entirely within the compressive stress zone.

The cathedral in Sevilla is the worlds largest Gothic style church and has some really impressive flying buttresses.

I found Segovia's cathedral. Buttresses from inner column line to the outer wall.

As long as I've already turned this thread into a travel blog...

Arches in the largest church in the world in nearby Cordoba, previously a mosque, while not having flying buttresses, are none the less impressive. Originally 720 columns. If you are ever in Spain, don't miss this. I'd rather see this one again than go to St. Paul's, Vatican City. I think I am due for another visit soon.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[IRstuff]

Then, there's Sagrada Familia, which is steel-reinforced concrete construction

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[1503-44]

I didn't know that. Seems rebar started being added in 1918. Probably a good move.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[IRstuff]

Some steel-reinforcement; the bottoms of those columns are stone, but I think there's steel inside

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