Sample of ancient Roman maritime concrete from Pozzuoli Bay near Naples, Italy. Its diameter is 9 centimeters, and it is composed of mortar formulated from lime, volcanic ash and chunks of volcanic tuff. (Carol Hagen photo)
Posted on 06/05/2013 9:16:34 AM PDT by Renfield
In a quest to make concrete more durable and sustainable, an international team of geologists and engineers has found inspiration in the ancient Romans, whose massive concrete structures have withstood the elements for more than 2,000 years.
Sample of ancient Roman maritime concrete from Pozzuoli Bay near Naples, Italy. Its diameter is 9 centimeters, and it is composed of mortar formulated from lime, volcanic ash and chunks of volcanic tuff. (Carol Hagen photo)
Using the Advanced Light Source at Lawrence Berkeley National Laboratory (Berkeley Lab), a research team from the University of California, Berkeley, examined the fine-scale structure of Roman concrete. It described for the first time how the extraordinarily stable compound – calcium-aluminum-silicate-hydrate (C-A-S-H) – binds the material used to build some of the most enduring structures in Western civilization.
The discovery could help improve the durability of modern concrete, which within 50 years often shows signs of degradation, particularly in ocean environments.
The manufacturing of Roman concrete also leaves a smaller carbon footprint than does its modern counterpart. The process for creating Portland cement, a key ingredient in modern concrete, requires fossil fuels to burn calcium carbonate (limestone) and clays at about 1,450 degrees Celsius (2,642 degrees Fahrenheit). Seven percent of global carbon dioxide emissions every year comes from this activity. The production of lime for Roman concrete, however, is much cleaner, requiring temperatures that are two-thirds of that required for making Portland cement.
The researchers’ findings are published in two papers, one that appears online today (Tuesday, June 4) in the Journal of the American Ceramic Society, and the other scheduled to appear in the October issue of the journal American Mineralogist.
“Roman concrete has remained coherent and well-consolidated for 2,000 years in aggressive maritime environments,” said Marie Jackson, lead author of both papers. “It is one of the most durable construction materials on the planet, and that was no accident. Shipping was the lifeline of political, economic and military stability for the Roman Empire, so constructing harbors that would last was critical.”
Marie Jackson holds a 2,000-year-old sample of maritime concrete from the first century B.C. Santa Liberata harbor site in Tuscany. (Sarah Yang photo)
The research team was led by Paulo Monteiro, a UC Berkeley professor of civil and environmental engineering and a faculty scientist at Berkeley Lab, and Jackson, a UC Berkeley research engineer in civil and environmental engineering. They characterized samples of Roman concrete taken from a breakwater in Pozzuoli Bay, near Naples, Italy.
Building the Empire
Concrete was the Roman Empire’s construction material of choice. It was used in monuments such as the Pantheon in Rome as well as in wharves, breakwaters and other harbor structures. Of particular interest to the research team was how Roman’s underwater concrete endured the unforgiving saltwater environment.
The recipe for Roman concrete was described around 30 B.C. by Marcus Vitruvius Pollio, an engineer for Octavian, who became Emperor Augustus. The not-so-secret ingredient is volcanic ash, which Romans combined with lime to form mortar. They packed this mortar and rock chunks into wooden molds immersed in seawater. Rather than battle the marine elements, Romans harnessed saltwater and made it an integral part of the concrete.
The researchers also described a very rare hydrothermal mineral called aluminum tobermorite (Al-tobermorite) that formed in the concrete. “Our study provided the first experimental determination of the mechanical properties of the mineral,” said Jackson.
This scanning electron microscope image shows crystals of a rare mineral, Al-tobermorite, magnified about 25,000 times. UC Berkeley researchers characterized Al-tobermorite in samples of Roman concrete. (Image courtesy of UC Berkeley)
So why did the use of Roman concrete decrease? “As the Roman Empire declined, and shipping declined, the need for the seawater concrete declined,” said Jackson. “You could also argue that the original structures were built so well that, once they were in place, they didn’t need to be replaced.”
An earth-friendly alternative
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.”
The research began with initial funding from King Abdullah University of Science and Technology in Saudi Arabia (KAUST), which launched a research partnership with UC Berkeley in 2008. Monteiro noted that Saudi Arabia has “mountains of volcanic ash” that could potentially be used in concrete.
In addition to KAUST, funding from the Loeb Classical Library Foundation, Harvard University and the Department of Energy’s Office of Science helped support this research. Samples were provided by Marie Jackson and the Roman Maritime Concrete Study (ROMACONS), sponsored by CTG Italcementi, a research center based in Bergamo, Italy. The researchers also used the Berlin Electron Storage Ring Society for Synchrotron Radiation, or BESSY, for their analyses.
The EPA has classified fly ash from coal plants as a hazardous waste.
It just pi$$es me off royally that "carbon footprint" crapolla has to be inserted into everything. It immediately makes the whole thing suspect in the sense the reader has to wonder where else in the article has environmental PC been mixed in with (and thus contaminating) real science.
News Flash: Earth and its lifeforms are carbon based.
Ironically the Italian Mafia prefers the quick setting concrete.
Exactly...pozzolan-based concrete has been around forever.
Stopped reading at “carbon footprint”
I just about stopped reading when I saw the stupid carbon footprint crap.
Me too.
Exactly. As if the Romans cared about Global Warming.
You should understand the field of construction materials is loaded with LEED certified experts trying to market "sustainable" design products. LEED certification should make you vomit.
No doubt it would do just that
The Romans knew better than to build roads in Michigan.
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Yup....they just got the copper and went back home.
That is asphalt concrete., not portland cement concrete. The cement binder is asphalt, not portland cement.
The relatively thin asphalt concrete surface layer is designed to be replaced at intervals. The whole roadway is several feet thick and is comprised of a series of load bearing and distributing materials. Although the surface in the photo has deteriorated, the underlying road way remains intact.
The traffic and the loads of present day roads can not be logically compared to the Roman roadways.
Portland cement concrete roads are inflexible. The expansion of the inflexible material is accommodated with expansion joints. Over time, the concrete edges at the expansion joints wears away. The result is bumpity bumpity bumpity bumpity bump on an old road. The condition can never be really fixed. Sawing and re pouring the joints fails, paving over with asphalt concrete eventually pushes the asphalt down into the expansion joints with the same bumpity bumpity effect.
The problem you showed is not a design problem but rather a maintenance problem. They delayed the resurfacing too long
To be fair, Rome was not run by liberals...
Would fly ash (by-product of furnaces) be a reasonable substitute for volcanic ash and chunks of volcanic tuff?
The reason I ask is that 20 years ago a professor at UWM (Univrsity of Wisconsin Milwaukee) published a paper on adding fly ash to the concrete mix used in road projects to improve its durability. He estimated that the addition of fly ash (readily available and almost free) would increase a highway’s longevity to 30 years, whereas now they repave about every 5 years and the roads are in poor repair in the meantime. I believe that his idea came from studying Roman roads.
The professor’s suggestion drew no traction and no action from Wisconsin’s road builders. We figure that it is because it threatened the job security of the labor force who likes to repave every 5 years.
See reply #36.
We were in Beijing China a while back. It snowed a few inches and suddenly thousands of people with brush brooms, shovels, bicycles with plywood platforms appeared as if out of nowhere and began clearing the snow. I asked an English speaking guy why they didn’t use snow plows and blowers. He responded “but, then, where would these people find work?”
LOLOLOL!
Flyash is mostly oxides, whereas volcanic ash is mostly a mixture of fine silicates and hydrated alumino-silicates; chemicallyand physically, they are different.
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