Ancient Roman architecture
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, 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.
Le Corbusier
During World War I, Le Corbusier taught at his old school in La-Chaux-de-Fonds, He concentrated on theoretical architectural studies using modern techniques. In December 1914, along with the engineer Max Dubois, he began a serious study of the use of reinforced concrete as a building material. He had first discovered concrete working with Auguste Perret in Paris, but now wanted to use it in new ways.