How was concrete improved in ancient Rome?

Answer 1

The Romans made a better concrete by mixing a volcanic rock called pozzolana (which is named after Pozzuoli, a suburb of Naples) with lime as a binder and adding pottery shreds or rubble from bricks or stones as aggregates which added body to it. The choice of aggregate depended on what concrete was used for or how heavy or light it needed to be.

Roman concrete (opus caementicium) was as resistant as modern concrete and also set underwater (and therefore could also be used to build docks for ports, dams, aqueducts and bridges). Concrete had technical and practical advantages. It was exceptionally strong and could span great distances when shaped into arches, vaults or domes as it could be moulded. It was layered into a formwork and it took the shape of its container. It did not require skilled labour and therefore was cheaper. It was much faster for construction than laborious masonry walls. It was safer because concrete vaulted roofing was fireproof, unlike the wooden-beamed roofs of traditional construction post-and-lintel methods.

Concrete was one of the three elements which led to what historians call the Roman architectural revolution or concrete revolution. The other two were the barrel (simple) arch and the vaulted arch. These three elements enabled the Romans to go beyond Greek methods of construction which used post-and-beam or post-and-lintel structures. The Romans were the first to fully appreciate the advantage of these structures. The (simple, barrel) arch has a strong load- bearing capacity. . The vault (vaulted arch) has an even greater load-bearing capacity and its structure is suited to support large roofs. The vaulted arch came into two forms: the groin arch is formed by two to four intersecting barrel (simple) arches and the rib arch, where the intersecting arches were not of the same diameter; the ribbed arch has intersected arches of different diameter. Their construction in concrete made them easier to build and even stronger. This led to the use larger and monumental arches and vaults on a grand scale.