Made to Last

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The Pantheon in Rome has survived nearly intact for almost 2,000 years.

How is that possible, scientists have long wondered.

Recently, researchers at the Massachusetts Institute of Technology have figured out a few of the ancient tricks the Romans deployed to create structures that last for millennia, Smithsonian Magazine reported.

For their study, researchers took mortar samples from the walls of the ancient city of Privernum, near Rome. The samples had a similar composition to other Roman concrete structures from the same period.

They discovered that the mortar contained small chunks of calcium deposits known as lime clasts.

These deposits formed because Roman engineers used the most reactive form of limestone, called quicklime – instead of or in addition to slaked lime – which is combined with water first. This mixture causes a chemical reaction that results in hot temperatures – known as “hot mixing” – and forms the calcium deposits.

The team suggested that this method was ingenious: When water entered the cracks in concrete, the calcium would dissolve and then recrystallize – or react with other materials – to fill the fissures and strengthen the structure.

They tested this theory by creating concrete using a Roman recipe and a modern recipe. They then broke the concrete and let water pass through for 30 days.

Only the Roman concrete blocked the water flow.

Besides illustrating Rome’s advanced engineering, researchers said, the study could help engineers create more durable modern concrete.