Why Ancient Roman concrete lasts for millennia but ours crumbles in decades

Scientists solve the mystery of why 2000-year-old Roman concrete still stands strong.

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 brace for 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.

 

mary-beard-on-sexual-practices-of-ancient-romans

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.

Researchers, led by University of Utah geologist Marie Jackson, looked at the microscopic structures of Roman concrete samples by subjecting them to numerous spectroscopic tests and imaging techniques. The tests showed a rare reaction took place that spurred the growth of aluminous tobermorite crystals. Further geology detective work proved that the crystals were formed when seawater percolated through the little cracks in the Roman concrete, reacting to the mineral phillipsite, found in volcanic rock.

Jackson expressed her admiration for the genius of the Romans - 

“They spent a tremendous amount of work [on developing] this – they were very, very intelligent people,” said Marie Jackson.

Structures like the Pantheon and Trajan’s Markets in Rome were also built with this kind of concrete.

Roman author Pliny the Elder, who wrote the ancient world’s famous science tract “Natural History” once praised Roman concrete, writing “that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass, impregnable to the waves." 

Indeed, that’s proven to be true. 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.

Check out this video from the University of Utah on how seawater strengthens Roman concrete:

Read the study in American Mineralogist.

​Is science synonymous with 'truth'? Game theory says, 'not always.'

Good science is sometimes trumped by the craving for a "big splash."

Videos
  • Scientists strive to earn credit from their peers, for grants from federal agencies, and so a lot of the decisions that they make are strategic in nature. They're encouraged to publish exciting new findings that demonstrate some new phenomenon that we have never seen before.
  • This professional pressure can affect their decision-making — to get acclaim they may actually make science worse. That is, a scientist might commit fraud if he thinks he can get away with it or a scientist might rush a result out of the door even though it hasn't been completely verified in order to beat the competition.
  • On top of the acclaim of their peers, scientists — with the increasing popularity of science journalism — are starting to be rewarded for doing things that the public is interested in. The good side of this is that the research is more likely to have a public impact, rather than be esoteric. The bad side? To make a "big splash" a scientist may push a study or article that doesn't exemplify good science.

People who constantly complain are harmful to your health

Moans, groans, and gripes release stress hormones in the brain.

Photo credit: Getty Images / Stringer
popular

Could you give up complaining for a whole month? That's the crux of this interesting piece by Jessica Hullinger over at Fast Company. Hullinger explores the reasons why humans are so predisposed to griping and why, despite these predispositions, we should all try to complain less. As for no complaining for a month, that was the goal for people enrolled in the Complaint Restraint project.

Participants sought to go the entirety of February without so much as a moan, groan, or bellyache.

Keep reading Show less

NASA and ESA team up for historic planetary defense test

Two space agencies plan missions to deflect an asteroid.

ESA's Hera mission above asteroid 65803 Didymos. Credit: ESA/ScienceOffice.org
Surprising Science
  • NASA and the European Space Agency (ESA) are working together on missions to a binary asteroid system.
  • The DART and Hera missions will attempt to deflect and study the asteroid Didymoon.
  • A planetary defense system is important in preventing large-scale catastrophes.
Keep reading Show less