Engineering · Roman Empire Daily
Roman builders could pour concrete that hardened underwater, letting them build harbors out in the open sea.
Deep dive
By using volcanic ash from Pozzuoli, Roman marine concrete cured through a chemical reaction even when submerged. This let engineers construct massive harbor works, such as at Caesarea Maritima, where no natural harbor existed.
Source: Vitruvius, 'On Architecture,' 2.6; Brandon et al., 'Building for Eternity,' 2014.
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