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.

Should you defend the free speech rights of neo-Nazis?

Former president of the ACLU Nadine Strossen discusses whether our society should always defend free speech rights, even for groups who would oppose such rights.

Sponsored by Charles Koch Foundation
  • Former ACLU president Nadine Strossen understands that protecting free speech rights isn't always a straightforward proposition.
  • In this video, Strossen describes the reasoning behind why the ACLU defended the free speech rights of neo-Nazis in Skokie, Illinois, 1977.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less

Harness the Power of Calm

Tap into the "Rest and Digest" System to Achieve Your Goals

Big Think Edge
  • In the fast-paced workplaces and productivity-focused societies many of us inhabit today, it is easy to burnout.
  • Emma Seppälä, a Stanford researcher on human happiness, recommends tapping into the parasympathetic nervous system instead—"rest and digest"rather than "fight or flight."
  • Aiming for energy management rather than time management will give you the resilience you need to excel at the things that really matter in your life and career, rather than living "mostly off" by attempting to seem "always on."

Apple co-founder says we should all ditch Facebook — permanently

Steve Wozniak doesn't know if his phone is listening, but he's minimizing risks.

Photo by Bryan Steffy/Getty Images
Technology & Innovation
  • Steve Wozniak didn't hold back his feelings about the social media giant when stopped at an airport.
  • The Apple co-founder admitted that devices spying on his conversations is worrisome.
  • Wozniak deleted his Facebook account last year, recommending that "most people" should do the same.
Keep reading Show less

Where the evidence of fake news is really hiding

When it comes to sniffing out whether a source is credible or not, even journalists can sometimes take the wrong approach.

Sponsored by Charles Koch Foundation
  • We all think that we're competent consumers of news media, but the research shows that even journalists struggle with identifying fact from fiction.
  • When judging whether a piece of media is true or not, most of us focus too much on the source itself. Knowledge has a context, and it's important to look at that context when trying to validate a source.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less