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Potential breakthrough in Roman Concrete

 
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Haven't been around in a while, but I saw this article and thought of everyone here. Roman Concrete has been an enigma for a long time--it's strong and durable without the need for support like rebar.

Anyway, looks like some scientists may have made a breakthrough in discovering its secrets. Could be big

https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-so-durable

I don't know if the process will be viable at a home level, but could be something to consider when planning buildings.

 
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Awesome. I'm already thinking about finding a source of quicklime so that I can try this.
 
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Wow, that would really help with hydrodams if the concrete was self-healing on cracks.

I know dams have a huge amount of rebar in them, not because they need the rebar for strength per se, but to help eliminate microcracking. If concrete could be self-healing in terms of cracking, they could use a lot less rebar offsetting the higher cost of hot-mixing.

Very interesting.
 
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Cheers for sharing!  I've always assumed that Roman Concrete was our first (so far) confirmed example of geopolymers, and this seems to confirm that.  

We live on volcanic soils, so super stoked to try this out sooner rather than later.
 
Kyle Clawson
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Phil Stevens wrote:Awesome. I'm already thinking about finding a source of quicklime so that I can try this.



If you do, give us a report!
 
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A concrete breakthrough seems like a bad thing to me.
 
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I'm not sure the article isn't just rebranding the topic for views. I had never heard that the Romans used slaked lime in concrete. I always thought they used quicklime. Why would they slake the lime? Remember that all this was done by hand back then.  Why add an extra laborious step to the process if not necessary? Why make the lime heavier for transport? I would imagine most projects large enough to warrant concrete would have been large enough to warrant making the quicklime on site. I would imagine it would have been most efficient to simply make it and use it directly. Who knows, maybe they even used it before it had cooled off, adding even more heat to the process.

As for the chunks of lime, it might be easy to put the quicklime in a machine today and have it come out as a powder at the other end, but back then it had to be ground up by hand. I'm not saying the chunks do not provide some advantage to the healing process, but I think there's a good chance they just ground it up just enough to do the job. I'm curious how much they affect the healing process. As we see from relatively modern lime mortar, the healing process happens just fine with an evenly powdered lime with no chunks. As I recall, it is carbon dioxide that reacts with the lime to cure it and to help it self-heal.  When fresh lime is exposed by a crack, it can react. Any that is hidden away below the surface doesn't get a chance to react until it is exposed, whether it is a chunk or not. I'm not really sure what's going on here.
 
Phil Stevens
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Jordan, I think the key difference here is in the mixing process. Quicklime + water = slaked lime, which over time will carbonate and turn back into limestone. If you mix the quicklime with water by itself and let it sit, you get lime putty, which is the preferred form for masonry work and plasters. Stores of lime putty have been found in old European buildings that were centuries old and still usable...it improves with age and there were even Roman laws requiring a minimum of three years of sitting after mixing before it could be used. Clasts are pretty much nonexistent in aged lime putty and the process of turning into stone is slow. The restorers of heritage structures have found that mortar on the interior of thick stone walls was still plastic centuries after they were built.

Because of this accumulated knowledge, the people researching Roman concrete assumed that lime putty was the basis of the product. The assumption up until now has been that the pozzolan was the secret sauce, but in the discovery and analysis of the clasts we're seeing that they most likely threw in some quicklime when the rest of the mix was finished. I would guess that this acted a lot like putting a handful of flour all at once into a pan of gravy that's cooking: you get a lot of lumps. So next time I have a project that fits the bill, I'll giving this a spin.
 
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My contribution here is based on hearsay and limited understanding but it might be valuable.

Getting lumps of lime incorporated into concrete might improve durability- and I purely love the idea of self mending concrete, but won’t it be just as energy intensive as modern conventional Portland cement, because isn’t that how cement is manufactured?  By burning limestone?

A very smart civil engineer told me the secret to the strength of Roman concrete was the ash.

Looks like this article says the Roman’s used volcanic ash, which my engineer friend said could be substituted with “fly ash” which is a byproduct of burning coal.
 
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I thought they used 'salt' seawater for concrete. Not fresh water. Can't wait till studies give us the recipe.
 
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Sounds like a form of geopolymer like Davidovits has researched. An aluminosilicate rock powder or volcanic or fly ash reacted by a strong alkaline solution and then heated to form a strong polymeric structure.
 
John Craig
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FYI   Steve Shelton posted his batch box rocket mass heater using ITGS (low temperature geopolymer settings) on the rocket mass heater thread of this web site. He gives the recipie he used, if you want to make some geopolymer yourself.
 
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Dan Fish wrote:A concrete breakthrough seems like a bad thing to me.



Chuckles...
 
Cécile Stelzer Johnson
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Steve Zoma wrote:Wow, that would really help with hydrodams if the concrete was self-healing on cracks.
I know dams have a huge amount of rebar in them, not because they need the rebar for strength per se, but to help eliminate microcracking. If concrete could be self-healing in terms of cracking, they could use a lot less rebar offsetting the higher cost of hot-mixing.
Very interesting.




And if it could be scaled down, ponds too, either for swimming of adding wildlife. Now, where could I get volcanic ingredients? in Central Wisconsin?
 
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Phil Stevens wrote: Clasts are pretty much nonexistent in aged lime putty and the process of turning into stone is slow. The restorers of heritage structures have found that mortar on the interior of thick stone walls was still plastic centuries after they were built.



plastic on the inside = flexible, which to me means that during seismic activity, the building would wiggle a bit. Then, if it cracked, that would heal over time after the wiggling. Sounds kind of awesome.

I would love to give this a try but I live in a No Volcano area.
 
Thomas Crow
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I live near a volcano and have good soils for this (which, seemingly, makes them bad for rammed earth).  Patent after patent suggests our allophanic clays are perfectly acceptable for geopolymers.  I just struggle to find a recipe I can understand/follow.

My goal is to have this sorted by the end of the summer.  It will change so much about our property if we could just pour stone.
 
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Here be the paper...

https://www.science.org/doi/epdf/10.1126/sciadv.add1602
 
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From what I remember Roman concrete also requires hydraulic pressure as it was a technique developed originally from rammed earth. Supposedly the story goes that they were building a wall in Pozzuoli using rammed earth which they would cover in lime plaster to keep it from weathering, and the lime reacted with the Volcanic ash in the soil. So a lot of the structures still used that technique of rammed earth just with roman cement instead of soil. In fact theirs a number of different recipes using different pozzolana that were used in construction from crushed fired clay to grain hulls. So my recommendation is if your looking for an alternative building material I'd look at stabilized rammed earth or CEB's and if you don't have soils rich in pozzolana their are modern pozzolana that can be imported and used such as fly ash, steel slag, metakaolin, rice hulls, diatomaceous earth, etc. Each has their own properties so some investigation might be warranted, but if you live in a region that produces any of them then you may be able to get some cheaply. And as a last resort I know wood ash varies in chemical composition depending on temperature of combustion, you may be able to make fly ash or bottom ash from wood instead of coal. And lastly for those here who may be less DIY inclined, though unlikely, Gigacrete is a interesting pozzolana material made from fly ash that has the bonus of being highly impact resistant, like class 4 bullet proof, hurricane proof, water proof, small missile blast proof. So if your building a structure in a war zone, like downtown Chicago, you might want to consider it.        
 
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The Ten Books On Architecture by Vitruvius (Roman Military and Civilian Engineer) c.20 BCE

https://en.wikisource.org/wiki/Ten_Books_on_Architecture
 
Phil Stevens
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@Thekla - both processes are energy intensive but cement production requires higher temperatures and uses considerably more.
 
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Amazing...what other simple technologies have we actually lost to time?
 
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Thomas Crow wrote:Cheers for sharing!  I've always assumed that Roman Concrete was our first (so far) confirmed example of geopolymers, and this seems to confirm that.  

We live on volcanic soils, so super stoked to try this out sooner rather than later.



yeah this development is great ... theyve pinned it down i guess, cant believe they didnt have this earlier...it was mostly meditrranean locations so good for saltwater coast living...bet Surfside wouldnt have happenedif they used ancient roman concrete...
 
arianna higgins
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Phil Stevens wrote:@Thekla - both processes are energy intensive but cement production requires higher temperatures and uses considerably more.



i wonder if we could use the Roman technique for 3D printing a home?
 
Cécile Stelzer Johnson
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john pannacciulli wrote:Amazing...what other simple technologies have we actually lost to time?



An interesting concept, John. While we have research centers, schools and all sorts of ways to learn more, better and faster and transfer knowledge and with the budgets to match, the idea that we could somehow "lose" knowledge is really interesting to me, a retired teacher..
Today, we consider trepanation [essentially making a hole in someone's head] to be a very serious operation, fraught with dangers of infection, of unendurable pain.
Yet, skulls have been uncovered dating back to pre-literate societies and the many skulls recovered show that most patients lived long after the trepanation. They have been done with very primitive tools, some with a sharp stone slowly grinding at the skull. In the middle ages, however, in France specifically, it was considered sacrilegious to open a person's body. [The logic was, in a nutshell: God made the body and who are we to try and 'fix' God's work] Anesthesia and antibiotics were not in use. Henri II of France had a wound that did not penetrate the cranium but the lance that broke in his eye while he was jousting eventually caused an infection that killed him. He could probably have been saved had we understood sepsis/ infection. Yet so many humans, all over the world, in every civilization survived trepanations long before Henri II.
Similarly, before Pasteur, most women had children at home, with a midwife, very successfully. Women would often prefer to die at home than be seen by a 'proper' doctor in the hospital if they had a difficult pregnancy. Even though this was in the 19th Century, doctors had a very limited understanding of infection and failed to wash their hands between patients... with the catastrophic results you can imagine.
The concept of zero was known to the Mayans and to the people of India while in Europe, Roman numerals were used.
Hmmm. Reading my post, I realize that I strayed far from the topic of Roman Concrete. I hope you will forgive me.
Considering that we tend to be very ethnocentric and feel that we are superior to pre-literate humans and think of them as tough, bearded, unknowing boors, riddled with crazy superstitions, I just thought that we can all use a bath of humility once in a while and keep our minds wide open... Maybe we should respect our ancestors a lot more...
 
John Craig
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Cecile:

You asked where would you get volcanic ash where you live?  You don't need volcanic ash. You need a pozolan, of which volcanic ash is one kind. Pozolans are a broad category of aluminuno silicate compounds like feldspar,  clays, zeolite, diatomacious earth, perlite and other aluminosilicates, many of which you can purchase at pottery supply stores. They are mixed with strong alkaline solutions of water and things like NaOh ( sodium hydroxide or lye crystals) KOh ( potasium hydroxide crystals). Both of which are used in soap making. You can also use quick lime which is also highly alkaline.
If you are interested, Google "geopolymers" or go to Steve Shelton's post on LTGS (low temperature geopolymer systems) in the rocket mass heater thread on Permies.
 
Phil Stevens
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Ground up perlite is a really good pozzolan. Most pumice is as well, and we have a nearly endless supply of the latter washing up on our beaches.

@Thomas, it looks like several lime producers sell quicklime around the motu. Graymont makes it at their Te Kuiti plant and I'm pretty sure that Hatuma is making it in central Hawkes Bay (not too far from me).
 
Thekla McDaniels
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Hi Philip

When you say pumice, I wonder if all volcanic rocks full of ‘air’ bubbles qualify.  We have pumice that is obsidian with frothy bubbles they cut into bars for cleaning hard water deposits off of porcelain.  It has a very distinctive smell, and there are local volcanic rocks from pebble to boulder size, full of holes roughly pea size.  

How can I find out if they are both pozzolans?

Thanks
 
Phil Stevens
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The way I test for pozzolanic potential is pretty crude. I start with unadulterated lime putty, divide it into two parts, and mix one of the parts with whatever it is that I'm testing. Then I make a test "cast" with both batches side by side (usually this is a layer of plaster about 1 cm thick) and then compare things like the speed of cure, how hard it gets, how waterproof it is after a period of time, etc.

With pumice, it's pretty easy to crush some into powder and try it out. This is admittedly not a full materials science testing protocol...just a suitability benchmark. I've used brick dust, wood ash, pumice, perlite, and biochar with varying degrees of pozzolanic activity. The pumice was probably the best of the bunch, but ash from hardwood was surprisingly effective for my purposes.
 
Thekla McDaniels
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Good to know!  

It’s probably how the Romans did it!
 
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Phil Stevens wrote:Jordan, I think the key difference here is in the mixing process. Quicklime + water = slaked lime, which over time will carbonate and turn back into limestone. If you mix the quicklime with water by itself and let it sit, you get lime putty, which is the preferred form for masonry work and plasters. Stores of lime putty have been found in old European buildings that were centuries old and still usable...it improves with age and there were even Roman laws requiring a minimum of three years of sitting after mixing before it could be used. Clasts are pretty much nonexistent in aged lime putty and the process of turning into stone is slow. The restorers of heritage structures have found that mortar on the interior of thick stone walls was still plastic centuries after they were built.

Because of this accumulated knowledge, the people researching Roman concrete assumed that lime putty was the basis of the product. The assumption up until now has been that the pozzolan was the secret sauce, but in the discovery and analysis of the clasts we're seeing that they most likely threw in some quicklime when the rest of the mix was finished. I would guess that this acted a lot like putting a handful of flour all at once into a pan of gravy that's cooking: you get a lot of lumps. So next time I have a project that fits the bill, I'll giving this a spin.



It's still not adding up in my head. Quicklime plus a stoichiometric amount of water makes slaked lime, which is still powdery. This is the kind of lime we can buy in a store that sells masonry supplies. Slaked lime plus carbon dioxide makes calcium carbonate (limestone). Slaked lime plus more water makes lime putty. The extra water prevents contact with carbon dioxide, allowing the lime putty not to turn to limestone. On a large stone wall, the mortar may not be dry, but I think on a typical fired brick wall of more modern construction, the mortar would completely dry, but the thing about non-hydraulic lime mortar is that it is able to reabsorb water, which was an essential function in its day. Repairs to old walls with new Portland cement mortar is often disastrous because it does not allow water to exit the interior of the wall resulting in damage to the building. I presume the thixotropic nature of the mortar does not really require the mortar to completely dry and harden in order to do its job, especially if the outside surface of the mortar in contact with the air carbonates and becomes permanently solid, holding the inner mortar in place. I can understand the reason for aging lime putty for making plaster. It must be smooth to spread evenly on a wall for a good finish. This still leaves the question of why would they go to all that trouble to make and store for three years a product if it was not necessary? That would add a tremendous amount to the cost of manufacture, and the lime putty would be even heavier (much heavier) than slaked lime to transport. And due to its thixotropic nature, it would need to be transported in watertight containers like amphora or it would liquify and ooze out of a cart while moving, which would add considerably more weight. They could spend all that time and money, or they could just burn the limestone/shells, crush them in a mortar and use them. I know which way I would try first. I just don't see why the people studying it would assume they used the expensive, premium grade of lime to make it when the coarse chunks of lime were clearly visible in the ancient concrete.

Another question came to mind. What is the most logical way this started? Did some Roman engineer say one day, "I think today I will add some larger chunks of lime to my concrete so that it will have self-healing properties."? Or would it make more sense to imagine the ancients starting out by making the lime "just good enough" to get the job done from the start to save time and money? Maybe they noticed it had self-healing properties, maybe they didn't. I imagine it would have been likely that at least at some point someone would have said, "I want to have the best concrete in the empire; I shall use the best, aged lime putty available to make my concrete." Then they realized it worked no better (or maybe even worse) than the concrete with the chunks of lime in it, so they went back to using the easier way. It reminds me of the experts who say the ancients used copper chisels to shape granite. When it's pointed out that granite is much harder than copper, they simply respond, "Well, they probably had to sharpen them often." I'm still getting the feeling that they are just looking for attention. Here's a wikipedia article that discusses geologist Marie Jackson and her team recreating the lime/pozzolan mortar and studying and explaining its self-healing properties in 2014:  https://en.wikipedia.org/wiki/Self-healing_material

The ancient Romans used a form of lime mortar that has been found to have self-healing properties.[3] By 2014, geologist Marie Jackson and her colleagues had recreated the type of mortar used in Trajan's Market and other Roman structures such as the Pantheon and the Colosseum and studied its response to cracking.[4] The Romans mixed a particular type of volcanic ash called Pozzolane Rosse, from the Alban Hills volcano, with quicklime and water. They used it to bind together decimeter-sized chunks of tuff, an aggregate of volcanic rock.[3] As a result of pozzolanic activity as the material cured, the lime interacted with other chemicals in the mix and was replaced by crystals of a calcium aluminosilicate mineral called strätlingite. Crystals of platey strätlingite grow in the cementitious matrix of the material including the interfacial zones where cracks would tend to develop. This ongoing crystal formation holds together the mortar and the coarse aggregate, countering crack formation and resulting in a material that has lasted for 1,900 years.



I'm not seeing much new stuff presented in the newer article. I get the impression that many people see this article as a major leap forward. I myself was fascinated by roman concrete years ago. I am still amazed every time I see a picture of the Pantheon dome, or think of the other structures that have stood for two millennia. I think it's still really neat and could definitely have a place today. I like experimentation and do not want to discourage it. As much as it pains me to say it, there is a reason Portland cement was invented and is used almost exclusively today. It is relatively cheap, fast, reliable, and strong. It is on average ten times stronger than roman concrete, and that is just the cheap, fast version. It can be made much stronger if chosen. Since it contains lime, pozzolans will also work just as they do in roman concrete. They act like they are just now figuring out how roman concrete works. Maybe there are some nuances still unknown, but I think they pretty much know the ingredients, chemical reactions, main techniques, and could spend the R&D to make it just as good as the Romans, or better. There just isn't the financial incentive to do it. Many things can be done to make modern concrete stronger and more durable; they simply do not do them. It all comes down to the money. They make it just good enough to get the job done.

Roman concrete was also not poured like a liquid. It was like a cross between masonry and modern concrete. The rubble/coarse aggregate was generally placed and packed down by hand. Like many of the wonders of the ancient world, they had a secret ingredient to their projects we do not have today: slave labor. Without it, we simply can't afford to do many things they did back then. If a person wants a more environmentally friendly modern concrete that is superior to Portland cement concrete in virtually every way with a fraction of the carbon dioxide emissions, there is already a type of concrete on the market using calcium sulfoaluminate (CSA) cement, such as Rapid Set. It also costs several TIMES more...
 
Jordan Holland
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Thomas Crow wrote:Cheers for sharing!  I've always assumed that Roman Concrete was our first (so far) confirmed example of geopolymers, and this seems to confirm that.  

We live on volcanic soils, so super stoked to try this out sooner rather than later.




John Craig wrote:Sounds like a form of geopolymer like Davidovits has researched. An aluminosilicate rock powder or volcanic or fly ash reacted by a strong alkaline solution and then heated to form a strong polymeric structure.




Roman concrete is what's called a "crystalline hydration alkali activated cement," like Portland cement. The pozzolanic reaction creates interlocking crystals which cause the cement to set (and heal when damaged). It would therefore not be considered a geopolymer. A geopolymer is literally a polymer, and will have a more uniform molecular structure. Here is a good pic illustrating how the two structures compare by:

By JDavidovits - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=24317631
Portland_and_Geopolymer.jpg
portland cement and geopolymer molecules
portland cement and geopolymer molecules
 
Cécile Stelzer Johnson
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John Craig wrote:Cecile:
You asked where would you get volcanic ash where you live?  You don't need volcanic ash. You need a pozolan, of which volcanic ash is one kind. Pozolans are a broad category of aluminuno silicate compounds like feldspar,  clays, zeolite, diatomacious earth, perlite and other aluminosilicates, many of which you can purchase at pottery supply stores. They are mixed with strong alkaline solutions of water and things like NaOh ( sodium hydroxide or lye crystals) KOh ( potasium hydroxide crystals). Both of which are used in soap making. You can also use quick lime which is also highly alkaline.
If you are interested, Google "geopolymers" or go to Steve Shelton's post on LTGS (low temperature geopolymer systems) in the rocket mass heater thread on Permies.




Thank you so much for the tip, John. I might try for smaller projects. Central Wisconsin is extremely sandy, like 35 ft of sand under my house, and the soil... well, there really isn't any where you don't compost and mulch. [Think sand dune].. I would have to buy any amount of clay. I guess they sell zeolite sand as a pool filtration item. I buy plenty of perlite to start some plants. Diatomaceous earth is something I use a fair amount of for my chickens and for me too. This is very informative and I will look into it some more. Thanks.
 
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OK, I get that it is interesting that we might be able to reproduce "roman concrete". I'm just not sure why that is significant. It just seems like a slightly "better" form of modern concrete (and I'm not clear why it is better).  It is relatively easy to design smaller projects (eg homes) without large amounts of conventional concrete anyway, and that will still be an environmentally better option than less-bad alternative form of concrete.

But where concrete gets used on massive scales, this is a non-starter. Architects won't be designing large projects around it's use because it is insufficiently consistent in it's behaviour to be guaranteed safe and predictable in it's behaviour.

At best I think this will be a niche concept for individual enthusiasts.
 
Phil Stevens
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Michael Cox wrote:OK, I get that it is interesting that we might be able to reproduce "roman concrete". I'm just not sure why that is significant. It just seems like a slightly "better" form of modern concrete (and I'm not clear why it is better).  It is relatively easy to design smaller projects (eg homes) without large amounts of conventional concrete anyway, and that will still be an environmentally better option than less-bad alternative form of concrete.

But where concrete gets used on massive scales, this is a non-starter. Architects won't be designing large projects around it's use because it is insufficiently consistent in it's behaviour to be guaranteed safe and predictable in it's behaviour.

At best I think this will be a niche concept for individual enthusiasts.



That's fine. We're permies. We're not interested in mass scales. Slow and small steps. Appropriate technology.

The big wins for me are the reduction in embodied energy and carbon footprint plus the self-healing property, which is already a feature of lime mortar but apparently turbocharged by the presence of clasts. So if a handful of enthusiasts start messing around with it, and come up with interesting and useful applications, their experience can be replicated and spread. Sort of like RMH development...plant the seed, give it the right conditions, and see what grows.
 
arianna higgins
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Michael Cox wrote:OK, I get that it is interesting that we might be able to reproduce "roman concrete". I'm just not sure why that is significant. It just seems like a slightly "better" form of modern concrete (and I'm not clear why it is better).  It is relatively easy to design smaller projects (eg homes) without large amounts of conventional concrete anyway, and that will still be an environmentally better option than less-bad alternative form of concrete.

But where concrete gets used on massive scales, this is a non-starter. Architects won't be designing large projects around it's use because it is insufficiently consistent in it's behaviour to be guaranteed safe and predictable in it's behaviour.

At best I think this will be a niche concept for individual enthusiasts.



Ever hear of the Parthenon? Roman concrete held for MILLENNIA. Our concrete only holds for maybe a century at most.

https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106

They think it's something about the calcium in seawater having self healing properties, havent done ll my reading yet.
 
Jh Williams
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arianna higgins wrote:

Michael Cox wrote:OK, I get that it is interesting that we might be able to reproduce "roman concrete". I'm just not sure why that is significant. It just seems like a slightly "better" form of modern concrete (and I'm not clear why it is better).  It is relatively easy to design smaller projects (eg homes) without large amounts of conventional concrete anyway, and that will still be an environmentally better option than less-bad alternative form of concrete.

But where concrete gets used on massive scales, this is a non-starter. Architects won't be designing large projects around it's use because it is insufficiently consistent in it's behaviour to be guaranteed safe and predictable in it's behaviour.

At best I think this will be a niche concept for individual enthusiasts.



Ever hear of the Parthenon? Roman concrete held for MILLENNIA. Our concrete only holds for maybe a century at most.

https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106

They think it's something about the calcium in seawater having self healing properties, havent done ll my reading yet.




Yes, I have heard of the Parthenon.

It's a GREEK Temple, built in Athens, Greece, around the 5th Century BCE using marble, granite and other stone. It was a key fixture in Athenian culture in the Greek Empire.

It predated Roman Concrete by about 300 years.
 
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John Craig wrote:Sounds like a form of geopolymer like Davidovits has researched. An aluminosilicate rock powder or volcanic or fly ash reacted by a strong alkaline solution and then heated to form a strong polymeric structure.



Pretty sure Davidovits chemistry does not involve fly-ash or strong alkaline. The Liquid glass (alumionsilicate) effectively locks micro-particles into a crystal matrix to make stone akin to granite, but they do have to be microparticles which takes energy to produce.

If I had the three hundered euro to buy Davidovits book I would, but honestly I'd rather pitch in for a part of the cost  and gift it to Paul then trust he would tweezer some Permaculter gems from it.
 
Chris Kay
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Not to hijack this thread but I've been doing a lot of non-google searches on this subject of late. It feels good to document and share the results I've obtained here if you will allow OP.

I can not make any claims to the veracity of these reports but they intrigue me.

I like the idea of custom mould firebrick mantle for rocket mass heaters and locally produced ducting.


Alkali Activated Materials are NOT Geopolymers playlist in four parts total runtime 87:30
https://youtu.be/3QGUCHt0tDs

How to Make Sodium Silicate - Water Glass - viewtime 11:32
https://youtu.be/S_uVL8UZkH8

Paul Cook makes Geopolymer - viewtime 29:40
https://open.lbry.com/@PaulCook:1/this-will-change-the-way-you-look-at:2

Finally, just because the original linked article referenced 3d printing.

Jarett Gross reports on 3D Printed Geopolymer, The Pyramids & Roman Construction
viewtime 16:35
https://youtu.be/f8ZFwBILPg8

Tell me why this tech is not tempting, especially if you replace rebar with bamboo.
 
Chris Kay
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Evidence of pre-Roman geopolymer employing an Organic Caroxylic Acid binder.

A form of Caroxylic acid (Oxalic acid) can be found in Rhubarb a hardy perennial found in abundance between the English cities of Leeds, Bradford and Wakefield. The Rhubarb Triangle.

Could Rhubarb have been the binder that built the precursor to these cities out of their iconic Yorkshire stone?

[odysee]https://odysee.com/@PaulCook:1/who-is-the-architect-of-this-realm:f?r=EkDG5UdEgyDJt7xvTYtUvZwYfDk6ga31[/odysee]

 
I agree. Here's the link: https://richsoil.com/wood-heat.jsp
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