How Roman concrete could build better buildings now

Long regarded for a far more durable product, the 2,000-year-old recipe is also better environmentally than current processes.

By Bruce Kennedy Jun 24, 2013 2:34PM

Roman Temple in Pozzuoli, Bay of Naples, Italy (© Angela Sorrentino/E+/Getty Images)Here's a nerdy but exciting story that combines archeology, chemistry and infrastructure issues -- and it has an economic impact, too.

A team of international researchers say they've uncovered the chemical secrets of why 2,000-year-old Roman concrete has lasted so long, especially in breakwaters along some of the ancient empire's ports, compared with the modern recipe for concrete, which includes portland cement. And unlocking that secret, they say, may have long-term environmental benefits as well as help future building projects.

"It's not that modern concrete isn't good -- it's so good we use 19 billion tons of it a year," Paulo Monteiro with the U.S. Department of Energy's Lawrence Berkeley National Laboratory said in a press statement earlier this month. "The problem is that manufacturing portland cement accounts for 7% of the carbon dioxide that industry puts into the air."

Monteiro led the research team, which analyzed concrete samples taken from a submerged Roman breakwater in the Mediterranean Sea. The secret to its durability, they found, was a combination of limestone (heated and powdered into lime), volcanic rock and seawater. As the press statement noted, the Romans mixed the lime and volcanic ash into a mortar. They added volcanic tuff -- the rocks formed by explosive volcanic eruptions -- to the mortar and then packed the whole mixture into wood forms and submerged them.

"The seawater instantly triggered a hot chemical reaction," the press release said. "The lime was hydrated -- incorporating water molecules into its structure -- and reacted with the ash to cement the whole mixture together."

And even when seawater wasn't available, the Roman method used much less lime and lower baking temperatures than modern concrete. Researchers say along with cutting greenhouse emissions, adapting the Roman method could provide the world with a more durable concrete.

"In the middle 20th century, concrete structures were designed to last 50 years, and a lot of them are on borrowed time," Monteiro said. "Now we design buildings to last 100 to 120 years."

"The question remains: Can we translate the principles from ancient Rome to the production of modern concrete?" Marie Jackson, a research engineer at the University of California at Berkeley and part of the research team, told Bloomberg. "I think that is what is so exciting about this new area of research."

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Jun 24, 2013 4:38PM
I have wondered for a long time why Roman roads and structures continue to stand and ours fail dramatically after only 30 years.  Very interesting.
Jun 24, 2013 9:54PM
Rome's ruins are from 2000 years ago.  Detroit's ruins are from 50 years ago.  I think we are doing something wrong.
Jun 25, 2013 12:47AM
The fault with Detroit has much more to do with who lives there than the quality of the concrete......
Aug 21, 2013 10:21PM
Interesting but old and not very accurate news.  The type of cement that the Romans created in this case (such as in the artificial harbor at Caeserea, now part of Israel) was a Pozzolan cement.  This cement was aided in its water resistance by silica introduced by using the volcanic rock that was suitable for this purpose.  The material was called pozzolan cement by virtue of the fact that the Romans mined the material from Pozzuoli, Italy, an area near Naples. The ability to make Pozzolan cement was lost with the decline of the Roman empire but the secret of its water resistence was re-discovered by John Smeaton, the father of modern civil engineering.  He used it to create the the famous lighthouse at Eddystone in the English channel (its importance is underscored by the fact that the English minted a two pence piece coin commemorating its creation and its presence is mentioned in Herman Melville's novel, Moby Dick).  But the main ingredient of pozzolan cement is the same main ingredient found in modern cements, calcium carbonate.  And both processes require the heating of the calcium carbonate to the point of de-carbonization.  Therefor, both processes produce carbon dioxide.  So it is misleading to imply that somehow the Roman process would be more environmentally friendly.  Oh, and the Romans stoked their fires with wood and coal - not a very eco-friendly process.  They did, however, understand the importance of cooling the cement as it undegoes its exothermic transformation.  Something that modern scientists would do well to practice more often.  To assert that the sea water had more to do with it than that would be misleading - as is this entire article.
Aug 22, 2013 3:06PM
Thank you Tristan. In fact the photo accompanying this piece is of the Tempio de Serapide,  otherwise known as a marketplace, located in Pozzuoli, Italy. During the Roman era the town was called Puteoli which means "little wells." The city is referenced in Acts 28 as the place where the Apostle Paul landed and stayed for seven days on his trip to Rome to appear before Caesar. In all likelihood the Apostle went to this marketplace and spoke with the citizens of the town. This region is part of a larger area known as the Campi Flegrea or "Fields of Fire." The region is built on dormant volcanic land. On the hill above Pozzuoli is the Solfatara Volcano that is currently active in the form of mud pits and steam vents. Overall a truly beautiful and breath-taking town and people.    
Aug 21, 2013 7:31PM
most of the failures of modern concrete is due to the oxidation (rust) of the reinforcement bars
Aug 23, 2013 9:49PM
  During the times of the Roman activity, roads were designed to support horses and small horse drawn equipment that is dwarfed by today's vehicles that weigh tons. Modern society uses materials and aggregate that is readily available such as limestone. Other materials could be used, but we have become so used to products lasting no more than fifty years, we have agreed that it's ok for the shorter time frame. In addition to that, with the huge population in the world, what would people do if they couldn't repair things that are worn out, cracked and made useless over time?
Aug 21, 2013 8:57PM
and what will sea water do to the steel reinforcing bars?  I suppose we could use epoxy coated rebar but then we have to address what drives a lot of what gets built and how - money and the usual lack of it or at least the unwillingness to invest what we have now into the long term future.  We like the quick payoff and worrying about tomorrow then.  I can't imagine a lot of what we build out of concrete today will work without reinforcing so any future use of this recipe will have to incorporate a new way to keep it standing.
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