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Ancient Roman Concrete Is About To Revolutionize Modern Architecture
schwit1 sends this news from Businesweek:
"After 2,000 years, a long-lost secret behind the creation of one of the world's most durable man-made creations ever — Roman concrete — has finally been discovered by an international team of scientists, and it may have a significant impact on how we build cities of the future. Researchers have analyzed 11 harbors in the Mediterranean basin where, in many cases, 2,000-year-old (and sometimes older) headwaters constructed out of Roman concrete stand perfectly intact despite constant pounding by the sea. The most common blend of modern concrete, known as Portland cement, a formulation in use for nearly 200 years, can't come close to matching that track record. In seawater, it has a service life of less than 50 years. After that, it begins to erode. The secret to Roman concrete lies in its unique mineral formulation and production technique. As the researchers explain in a press release outlining their findings, 'The Romans made concrete by mixing lime and volcanic rock. For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms. The seawater instantly triggered a hot chemical reaction. The lime was hydrated — incorporating water molecules into its structure — and reacted with the ash to cement the whole mixture together.'"
Can this discovery of old stuff be patented today, or is the fact that the romans did it so long ago constitute prior art? Or will the argument go like "We don't have a treaty with the Roman Empire regarding Intelectual Property Rights, an nobody did this in our country yet, so sure, go ahead an patent it"...?
Question for religious people: where do unrepentant masochists go when they die?
Digitus impudicus ad hodierna effercio. MM anni? Mirum dictu!
Those who can make you believe absurdities can make you commit atrocities. - Voltaire
I find it odd that there are claims this is new information. Didn't Vitruvius describe it in his De Architectura, written about 15 BC?
http://en.wikipedia.org/wiki/De_architectura
Perhaps the story is confusing the known composition with some mechanism that the new study discovered.
So there's no such thing as lime and tuff? Of course we can use this method today, if they really have the formula now. I think Portland cement has been used for the last 200 years because it is cheap. This will not be as cheap, but in applications where corrosion is a particular issue, e.g. dams and in particular in salt and brackish water, it might likely be used.
I plan to build my next structure with Roman Concrete and Rearden Steel...
All right, but apart from the sanitation, medicine, education, wine, public order, irrigation, roads, the fresh water system and public health, what have the Romans ever done for us?
didn't most countries move to a first to file system? I'm pretty sure Julius didn't get to the Patent office on time for this one.
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The secret to Roman concrete lies in its unique mineral formulation and production technique.
Oh? Really? Its not becuase the Romans made sacrifices to Jupiter? They didn't make their concrete with a recipe given to them by ancients astronauts? The secret lies with thier recipe and technique? Who knew?
Python: 'And then suddenly you have a language which says "we're all stuck with whatever the whiniest coder wants".'
Cement is not concrete. Concrete is made of cement plus aggregate.
Researched and published over 30 years ago. Known technology for decades. Could reduce the 7 % of total carbon dioxide output on planet generated by cement production.
Anything changed in 3 decades - will anything change in the near future in a billion $ industry?
BOHA!
From http://newscenter.berkeley.edu/2013/06/04/roman-concrete/ While Roman concrete is durable, Monteiro said it is unlikely to replace modern concrete because it is not ideal for construction where faster hardening is needed. But the researchers are now finding ways to apply their discoveries about Roman concrete to the development of more earth-friendly and durable modern concrete. They are investigating whether volcanic ash would be a good, large-volume substitute in countries without easy access to fly ash, an industrial waste product from the burning of coal that is commonly used to produce modern, green concrete. “There is not enough fly ash in this world to replace half of the Portland cement being used,” said Monteiro. “Many countries don’t have fly ash, so the idea is to find alternative, local materials that will work, including the kind of volcanic ash that Romans used. Using these alternatives could replace 40 percent of the world’s demand for Portland cement.”
Application specific concrete that has stood up for two millenia beats our common, everyday, casual-use concrete. Compare it to the stuff used for capping deep water oil wells and I'll be more impressed. [/sarcasm]
Those people who think they know everything are a great annoyance to those of us who do. (Isaac Asimov)
From http://en.wikipedia.org/wiki/Pozzolana
Cook D.J. (1986) Natural pozzolanas. In: Swamy R.N., Editor (1986) Cement Replacement Materials, Surrey University Press, p. 200.
Lechtman H. and Hobbs L. (1986) "Roman Concrete and the Roman Architectural Revolution", Ceramics and Civilization Volume 3: High Technology Ceramics: Past, Present, Future, edited by W.D. Kingery and published by the American Ceramics Society, 1986; and Vitruvius, Book II:v,1; Book V:xii2.
McCann A.M. (1994) "The Roman Port of Cosa" (273 BC), Scientific American, Ancient Cities, pp. 92–99, by Anna Marguerite McCann. Covers, hydraulic concrete, of "Pozzolana mortar" and the 5 piers, of the Cosa harbor, the Lighthouse on pier 5, diagrams, and photographs. Height of Port city: 100 BC.
Mertens, G.; R. Snellings, K. Van Balen, B. Bicer-Simsir, P. Verlooy, J. Elsen (2009). "Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity". Cement and Concrete Research 39 (3): 233–240. doi:10.1016/j.cemconres.2008.11.008. ISSN 0008-8846. Retrieved 2009-03-23.
I doubt whether it would help. Since Roman concrete can't be steel-reinforced, it would just crumble if ice heaved it upwards because it wouldn't have steel inside to hold it together. It wouldn't help with cracks, because even concrete roads are still surfaced with a few inches of asphalt (at least, in Florida... maybe things are different "up north"). AFAIK, the endless annual resurfacing would still be necessary, because 99% of the potholes and cracks are in the top layer of asphalt, not the structural concrete roadbed below.
Where the Roman concrete might be MORE useful is environments like causeways, by providing a hard shell around the structural foundation that protects it from erosion. Where it might become a bit dangerous is if it ends up protecting the structural reinforced concrete from VISIBLE damage, but doesn't prevent the steel from rusting away on the inside until its tensile strength gets reduced to the point of being dangerous even though it "looks fine" on the outside.(*)
(*)For those who don't know, reinforced steel consists of steel bars + concrete because concrete has tremendous compressive strength, but terrible tensile strength. Apply force in any direction besides straight down, and concrete just breaks away or crumbles. In contrast, steel has a lot of tensile strength (it tends to stretch and bend rather than snap), but terrible compressive strength. As a matter of good luck, steel & concrete have mostly identical expansion rates when heated & cooled, and form a very strong chemical bond to each other (get concrete splattered on your car, and once it dissolves the paint and makes contact with the steel body it's NEVER coming off). The combination allows concrete to provide the compressive strength, and the steel to provide the tensile strength. Without steel, an elevated freeway would have to be built from arched vaults. With steel, you can support it with flat beams. Of course, if you approximate a "classical" form like an arch, you'll be working WITH the concrete and adding strength, but steel is what allows us to build things like a 40 foot road deck cantilevered from a single support column, or support a skyscraper like Citigroup's midtown headquarters from support columns that are located in the middle of each wall instead of at the corners.
Admit it. You all learned Latin on the off chance that you would find yourself in the past left to survive by your own wits.
Or because it was compulsory in those days, at least at my school. And since it was taught the "old-fashioned" way (using sadistic brutality, such that the Centurion's Latin lesson in Life Of Brian was eerily familiar), I actually learned the cursed lingo.
All interesting or useful topics were forbidden. Time travel to escape your teachers and/or homework deadlines would have been one of these.
Those who can make you believe absurdities can make you commit atrocities. - Voltaire
Question is - why is it necessary for concrete to be reinforced? Obviously, the Romans didn't have steel or iron rebar. They formed and poured their structures without any rebar, and they've lasted a couple thousand years. It seems more than obvious that our architects and engineers can learn a few things from the Romans.
IANASE (structural engineer), but from my understanding one key difference that reinforced concrete confers is that it allows the concrete to be prestressed to perform better under tension. Concrete (Roman or modern) is just fine under compression, so it can support a prodigious amount of weight loading down on it. However, once you try to span an area then the concrete in the middle of the span is normally under tension. As you can imagine, this often leads to cracking and outright failure. Furthermore, it's why the Romans had such a predilection to using arches and domes, which keep the concrete predominantly under compression rather than tension.
Think about it this way: our highway bridges couldn't be built the way they are if we were using unreinforced Roman concrete; however, if the concrete is prestressed then the tensile forces are balanced by the compressive forces. This also allows us to do many other interesting things with architecture that weren't feasible before.
I have wondered about whether something like carbon fiber could be used in the future to produce prestressed concrete that wasn't as prone to corrosion as the steel rebar-based approach. Something like that might be the best of both worlds. Okay, so I just Googled and it looks like at least one carbon-fiber approach is already patented.
Just as an aside, the Romans were quite ingenious when it came to implementing their architectural application of concrete. I read that when Hadrian ordered the construction of the current version of the Pantheon, the Roman engineers were faced with difficulty designing a dome that would not collapse under its own weight (again, tensile forces and concrete are not friends). The Romans overcame this by reducing the density of the concrete in the dome by using pumice in the aggregate and reducing the thickness of the concrete as the dome progressed. The dome of the Pantheon remains the largest unreinforced concrete dome in the world—not because we can't replicate the techniques, but because reinforced concrete performs so much better under tension.
I'm sure that Roman concrete greatly varied in quality. Every batch was an experiment using local materials.The crap that didln't last for 25 year is long gone. All we have left to look at today are the results of successful experiments. And it is a wise thing to learn from it. But to consider everything the ancients built as evidence of their genius disregards the winnowing of time. Good stuff lasts, bad stuff falls apart and is discarded.
Even without prestressing, (which reinforced concrete does allow) reinforcement provides additional tensile strength. Concrete's tensile strength is no more than 10% of its compressive strength which means it's nothing to write home about. You can get reinforcement from fibres (which is why the ancients would add straw to clay to make bricks).
The point is that while pretensioning does give you added tensile resistance (by converting the inital tension to a reduction of the pre-imposed compression), reinforced concrete does not require pre-tensioning to reinforce concrete in tension, and in most cases just the presence of rebar is enough to provide the required tensile resistance. Pretensioning will be used when larger spans (and therefore larger tensile stresses in some parts of the beams) are required.
I like my dinosaurs feathery, and my pterosaurs hairy (or is it pycnofibery?)
From the headline one would think that this is the "secret ingredient" to the Roman concrete: "The lime was hydrated — incorporating water molecules into its structure — and reacted with the ash to cement the whole mixture together"
However, this is pretty much how portland cement (the modern binder in concrete) reacts with water to form the concrete with the agregate. Reading the article, however this is what matters:
"One is the kind of glue that binds the concrete’s components together. In concrete made with Portland cement this is a compound of calcium, silicates, and hydrates (C-S-H). Roman concrete produces a significantly different compound, with added aluminum and less silicon. The resulting calcium-aluminum-silicate-hydrate (C-A-S-H) is an exceptionally stable binder."
"At ALS beamlines 5.3.2.1 and 5.3.2.2, x-ray spectroscopy showed that the specific way the aluminum substitutes for silicon in the C-A-S-H may be the key to the cohesion and stability of the seawater concrete."
"Another striking contribution of the Monteiro team concerns the hydration products in concrete. In theory, C-S-H in concrete made with Portland cement resembles a combination of naturally occurring layered minerals, called tobermorite and jennite. Unfortunately these ideal crystalline structures are nowhere to be found in conventional modern concrete."
"Tobermorite does occur in the mortar of ancient seawater concrete, however. High-pressure x-ray diffraction experiments at ALS beamline 12.2.2 measured its mechanical properties and, for the first time, clarified the role of aluminum in its crystal lattice. Al-tobermorite (Al for aluminum) has a greater stiffness than poorly crystalline C-A-S-H and provides a model for concrete strength and durability in the future."
So basically, there is alimunium in the crystaline structure of Roman cement that contributes to the differences in performance over time (not raw strength). Another factor that may impact durability that is not covered here but that civil engineers will know well is the fact that modern cements are more alkaline than even early Portland Cement productions. As a result, they tend to react with the silicates in the aggregates of the cement (phenomenon known as alkali-aggregate reaction). If you see concrete with cracks that look wet even when it's not raining, that's a symptom of this effect. The reaction with the aggregates causes an expansion within the concrete which builds ups stresses locally and result in those cracks, with obviously unfortunate effects on the longevity of concrete structures.
I like my dinosaurs feathery, and my pterosaurs hairy (or is it pycnofibery?)
I am fairly certain it depends on the arch/dome curvature.
Good point. I should have said that a dome can be designed so that the stresses are primarily compressive. My point was that otherwise they wouldn't have been able to build the Pantheon with unreinforced concrete. I'm always amazed at how they managed to figure out good design rules without any mathematical stress analysis. Obviously they managed, though it may have involved a few things falling down or at least having to be patched up post-construction (not that that doesn't happen nowadays). Perhaps it also had to do with only slowly evolving their design/construction techniques, rather than making big leaps.
It makes sense: if you have a very low curvature the arch/dome trends toward being a flat beam and is obviously is experiencing tension.
I thought of the same "degenerate case is flat", and there must be a point where that becomes true, but if you have a dome that's a large portion of a sphere (e.g. 180 degrees), the tensile hoop stresses occur towards the bottom, and one way of dealing that is to reduce the portion of a sphere you're using (e.g. to 140 degrees). The whole "tending towards flat" may be covered by the fact that these simple analyses apply to domes that aren't "thin", which is defined by the ratio of the thickness to the radius. IIRC thin domes are structurally called shells.
Shame it's a Saturday, otherwise we'd almost certainly have some actual structural engineers chiming in. Some interesting references:
http://masonrydesign.blogspot.com/2012/03/thickness-of-dome-walls.html
http://site.iugaza.edu.ps/marafa/files/Spherical-dome.pdf
I will say that it is a shame we don't see as many flying buttresses anymore (haha).
Why haha? Not only are those cathedrals beautiful, but they sure do last (at least if you don't bomb them). IIRC they did have a few failures while they were working things out though.