Opus caementicium

Opus caementicium was the Roman technique of constructing structures using concrete. It was used from the beginning of the Roman republic through the whole history of the Roman empire.

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Opus caementicium, like other forms of concrete, is made from a mix of aggregate and a binder which, when mixed with water, hardens over time. In Roman times gypsum and lime were used as binders, but volcanic dusts such as pozzolona (found in central Italy) were favored where they could be obtained. Reinforcing elements (such as the steel bars used in modern construction) were not used.

In most usage the raw concrete surface was considered unsightly and some sort of facing was applied. Different techniques were characteristic of different periods and included:

• Opus incertum: small irregular stones
• Opus reticulatum: small squared blocks laid in a diamond pattern
• Opus quadratum: regularly laid courses of ashlars
• Opus latericium: regularly laid courses of brick
• Opus spicatum: brick laid in a herringbone pattern

References

ROMAN CONCRETE

Opus caementicium roman walls