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| Drilling at a marine structure in Portus Cosanus, Tuscany. Photo credit: J. P. Oleson. |
Scientists resolved the mystery of why coastal structures built by ancient Romans 2,000 years ago are still standing. The concrete used by Roman builders in piers and harbors was made in such a way that it grew even stronger over time. Modern concrete, by comparison, tends to decay in just decades when exposed to saltwater. These findings could have an important role to play as many communities worldwide face rising sea levels.
Romans created concrete by mixing volcanic ash, quicklime and chunks of volcanic rock. Even though they figured out the ingredients, scientists still didn’t know the recipe. How did the Romans manage to make the concrete so long-lasting? The key turned out to be in the chemical reaction caused by the addition of seawater.
The Roman concrete was made to interact with its environment, as opposed to modern concrete which stays inert and gets damaged over time. Seawater is the reason why the mixture gets stronger. As seawater reacts with volcanic material, new minerals are created that reinforce the concrete.
Structures like the Pantheon and Trajan’s Markets in Rome were also built with this kind of concrete.
Jackson is now working on recreating Roman concrete using seawater in San Francisco. This work might prove useful in building longer-lasting and stronger sea walls - a fact of growing importance. A study by European scientists predicts the costs of new coastal reinforcements will reach as high as $71 billion per year during the 21st century. Without them, coastal flooding will lead to trillions of dollars in damages.
