Roman Concrete Wasn't Lost. The People Who Made It Were.
Roman concrete was not lost. Roman concrete remains, embedded in the Pantheon’s dome and in thousands of bridges and aqueducts that have stood for two thousand years. Vitruvius wrote down the recipe in the first century BCE. The texts have been continuously available. The materials still exist. By any reasonable test, the information about Roman concrete has been with us the entire time. What was lost, for roughly 1,400 years, was the ability to make it....