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.
Ping
Of course, in America, one main ingredient in a lot of concrete is dead mobsters.
Here is the condition of Michigan roads by comparision:
Even back then, there was always some smart-ass telling the finishers “You don’t have to rub it, it’ll get hard.”
Jeez, and I thought it was to mix in the ashes of Christians. But OK, mobsters and union officials will do.
I wonder if the lava flows from recent volcano eruptions like St. Helens, Indonesian Mt. Tambora, and the Caribbean Monserrat could provide a new source of revenue to these areas—or if the shipping costs of the ash and tufa would be too costly?
They’re worse in Milwaukee.
/johnny
There was no lava flow from Mt St Helens.
But wasn’t there a lot of ash expelled into the surrounding areas? I think ash would be easier to ‘mine’ than hardened lava flow.
BTTT
Oh yes. There was oodles and gobs of ash...just no lava.
the Romans likely used slaves.
“...But OK, mobsters and union officials will do....”
Please add West Wing and Obamadork cabinet officials to the mix....although this addition will make the smell intolerable.
Despite all the eco nonsense this article is laced with, it’s interesting. Sounds like Montana could have been a major exporter after Mt. St. Helens erupted. That’s one way to get rid of all that ash, ship it elsewhere!
Roman legions provided the labor force for road construction. Built them as they went along into new territories to allow for transport of supplies and, if necessary, fast retreat. They built fortified camps wherever they stopped. They were master builders and the famous double siege wall around Alesia is just one example.
Grant money makes for a lot of study in the moot point area. We use fly ash because its cheap, cheaper than cement. They used volcano ash because it was cheap, cheaper than cement.
Good, glad thats over, but practical information for our Millions of Dollars in grants?
Zero.
And still the streets don’t get fixed.
Except Jimmy Hoffa. After his trip to the rendering plant, his remains were interred in the tummies of thousands of dogs.
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