Roman Concrete Ingredients at Pompeii Analyzed

CAMBRIDGE, MASSACHUSETTS—According to a Reuters report, Admir Masic of the Massachusetts Institute of Technology and his colleagues analyzed building materials discovered in a complex at Pompeii that includes a bakery and living areas. The structures were under renovation when Mount Vesuvius erupted in A.D. 79, burying the city in volcanic ash and preserving the work in progress at the bakery. Masic said the building materials demonstrate that the workers used a technique called “hot mixing” to make concrete as needed with quicklime, water, and a blend of volcanic rock and ash. When combined, these ingredients produce heat in a chemical reaction. Yet this method appears to contradict a recipe written by the Roman architect and engineer Vitruvius in the first century B.C. Roman hot-mixed concrete, however, contains remnants of lime from the reaction called lime clasts, which can dissolve, recrystallize, and repair cracks on its own, making it an improvement over the concrete described by Vitruvius. “Imagine what 100 years of difference could mean for the building technology,” Masic said. “This [hot-mixed concrete] allowed builders to construct massive monolithic structures, complex vaults and domes, and harbors with concrete that cured underwater,” he explained. Read the original scholarly article about this research in Nature Communications. To read about other structures made of Roman concrete, go to "Rome's Lost Aqueduct."