ANCIENT ROMANS were masters of concrete, fashioning concoctions of sand, water, and rock into long-lasting marvels. Bridges, stadiums, and other structures they built with the stuff still stand tall—even harbors and breakwaters that have been soaked by tides and storms for nearly 2,000 years. This substance, robust to the microscopic level, far outlives the modern material, which generally requires steel supports in salt water and is still likely to corrode within decades.
When the Roman Empire ended, so did its method of making marine concrete. But by following chemical clues within ancient architecture, today’s scientists have revived this technique. In recent years, researchers have only gotten better at understanding it, applying lessons from fields as diverse as archaeology, civil engineering, and volcanology. They have pulled tubes of the ancient substance…