Editing Ancient Roman architecture (section)

=== Roman concrete ===
{{Main|Roman concrete}}
[[File:OpusCaementiciumViaAppiaAntica.jpg|thumb|Example of ''opus caementicium'' on a tomb on the ancient [[Appian Way]] in Rome. The original covering has been removed.]]

Concrete quickly supplanted brick as the primary building material,{{citation needed|date=March 2016}} and more daring buildings soon followed, with great [[pillar]]s supporting broad [[arch]]es and [[domes]] rather than dense lines of columns suspending flat [[architrave]]s. The freedom of concrete also inspired the [[colonnade]] screen, a row of purely decorative columns in front of a load-bearing wall. In smaller-scale architecture, concrete's strength freed the [[floor plan]] from rectangular cells to a more free-flowing environment.{{Citation needed|date=July 2014}} Most of these developments are described by [[Vitruvius]], writing in the first century BC in his work ''[[De architectura]]''.

Although concrete had been used on a minor scale in Mesopotamia, Roman architects perfected [[Roman concrete]] and used it in buildings where it could stand on its own and support a great deal of weight. The first use of concrete by the Romans was in the town of [[Cosa]] sometime after 273 BC. Ancient Roman concrete was a mixture of [[lime mortar]], [[Aggregate (composite)|aggregate]], [[pozzolana]], water, and [[stones]], and was stronger than previously used concretes. The ancient builders placed these ingredients in wooden frames where they hardened and bonded to a facing of stones or (more frequently) bricks. The aggregates used were often much larger than in modern concrete, amounting to rubble.

When the framework was removed, the new wall was very strong, with a rough surface of bricks or stones. This surface could be smoothed and faced with an attractive [[stucco]] or thin panels of marble or other coloured stones called a "revetment". Concrete construction proved to be more flexible and less costly than building solid stone buildings. The materials were readily available and not difficult to transport. The wooden frames could be used more than once, allowing builders to work quickly and efficiently. Concrete is arguably the Roman contribution most relevant to modern architecture.