Volcanic sand has been credited with the longevity of Rome’s ancient monuments
washingtonpost.com
washingtonpost.com
François Coignet was a French industrialist of the nineteenth century, a pioneer in the development of structural, prefabricated and reinforced concrete. Coignet was the first to use iron-reinforced concrete as a technique for constructing building structures. In 1853 Coignet built the first iron reinforced concrete structure, a four story house at 72 rue Charles Michels in the suburbs of Paris. Coignet's descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning. [...]
> This study conclusively demonstrates that there is absolutely no evidence of an alkali-aluminosilicate-based composition in the binder phases of the casing stones, nor is there any evidence of “unusual” constituents in the pristine, bulk uncontaminated interior of the casing stones to call for a “man-made” origin. Despite the detection of a man-made “coating” on the Lauer casing stone, the stone itself is determined to be nothing but a high-quality natural limestone mineralogically, texturally, and microstructurally similar to that found in the quarries at Tura-Masara. ...
> Despite its many reported ancient routes, and unquestionable potential future applications of geopolymer technology, the Egyptian pyramids, in author’s opinion, still stand as marvels and mysteries of ancient engineering technologies exercised by the Old Kingdom (2500 BC) stone masons.
As a non-geochemist, I can say nothing about it one way or the other, and I know that I can be easily swayed by good sounding but wrong statements.
Perhaps it's like Thor Heyerdahl's Kon-Tiki. He showed that it was possible to go by balsa wood raft to Polynesia. That doesn't mean his diffusionist model of cultural development was what happened. That the Egyptians could have used geopolymer technology doesn't mean they did.
Roman concrete was called opus caementicium. The Romans had two main sources of the right kind of volcanic ash in Italy, the main one in Pozzuoli (http://en.wikipedia.org/wiki/Pozzolan) but apparently they mined other places, such as in Eifel where it is known as Trass (http://en.wikipedia.org/wiki/Trass). For example concrete was used in the very extensive aquaducts serving the Roman city that is now Cologne.
It is very similar to lime plaster (lime and sand) and so it is thought to have been discovered by simple substitution of local pozzolan for sand.
The advantage of Portland cement is that it cures very quickly. Roman cement takes something like a month to cure.
Another apparent advantage of Roman concrete is that they were able to throw up large structures with concrete vaults or domes with a large workforce in relatively short time frames, whereas the Medieval cathedrals (which were based initially on the same Roman basilica) took a smaller, highly skilled workforce long periods to cleverly piece together without concrete.
Pozzolan is used today, generally as an additive. Note that fly ash is similar (http://www.ctlgroup.com/lab-services/lab-tests/astm-c-618-co...). Again because of the long cure time the original Roman concrete is not in favor, but you may achieve the performance you need through the use of an admixture.
I should add that some of these recent articles may be linked to the general business interest in the increased use of pozzolanic admixtures, since there is a ready source in fly ash and also some parts of the world have vast amounts of pozzolanic ash ready to be exploited.
http://www.thegreatcourses.com/courses/understanding-greek-a...
If you enjoy history of architecture/engineering, it's worth picking up when it's on sale, the video quality is standard def, but you can either stream the videos or download DRM free copies of each lecture.
First of all, I bet that the strength of the concrete builds pretty slowly. They're mentioning a 180 day test, where most modern concrete is considered 'fully cured' at 28 days, and generally you're looking at a few days to a week before it's got enough strength to continue construction. (Note that concrete will continue to cure indefinitely as long as it's kept moist and at a good temperature. E.g., I looked at some concrete from a floating bridge that was 40 years old and it was 3x stronger than it was supposed to be based on the original specs. There's some scatter in those, but 40 years in a cool poist environment didn't hurt.) Also note that there are a lot of interesting additives to concrete that can change the behaviour of modern concrete, to make it easier to place, faster to set, slower to set, pumpable, high strength, high stiffness, or whatever.
Second, Concrete tends to be a pretty local thing. You don't tend to ship the raw materials long distances, since they're heavy and low value. In places where there is volcanic ash, it can be used. But then you get to places like the whole US east of the Rockies, and there's none of that.
Third, we lost the recipe for Roman Cement for the better part of 2 millennia, and only recently rediscovered it, well after the discovery of Portland Cement and it's spread through the world.
[1] http://en.wikipedia.org/wiki/Rosendale_cement
(Bonus factoid: while Rosendale cement is named or the location of the limestone deposits mined to produce it, Portland cement is named for the resemblance of the finished product to Portland stone, http://en.wikipedia.org/wiki/Portland_stone)
Those who find Roman concrete interesting, might want to look into various forms of artificial stone too (used in the 19th century): https://en.wikipedia.org/wiki/Artificial_stone
I believe they did have one and did use it - timber buildings. I think most ancient societies used timber but we don't see it now because it doesn't last. There's an article here on the find of "layer upon layer of Roman timber buildings, fences and yards" under London.
[0] https://en.wikipedia.org/wiki/Survivorship_biasAs for climate? Yes, the climate where I live (Ontario, Canada) is vastly more harsh than Rome (ancient or modern). Why do I bring this up? Because generally the people making these sorts of survivorship biased observations are also neglecting to control for other significant variables such as location.
You also didn't mention cost. Many of the great Roman structures which have survived to this day would have astronomical costs should we attempt to build them in the modern day using ancient building techniques and materials.
I'm not so convinced as far as materials are concerned. Techniques have improved and modern ones could be used (cranes etc.). The main issue I see here is that materials aren't even available anymore, nor are they legal w.r.t. building codes. So even if cost wasn't a factor, I don't see how anyone could build a modern building with Roman concrete, marble etc.
Certainly an igloo is a traditional architecture style where the result is meant to be thrown away.
This item isn't peculiar to modern architecture, particularly when it comes to large public buildings. If anything, modern architecture suffers a lack of ornamentation.
How is that secret?
Pozzolonic mortar ingredients have been know for a long time.
In fact, ashes have been used for making concrete for a long time too nowadays. Blast furnaces produce ashes that are routinely used for that.
Bad title. In the article then they say that what is secret is the reason why pozzolonic mortar withstand well time.
Sensationalist reporting...