More often than not, the aesthetic quality associated with concrete is its polished finish, achieved using steel plates, first popularized as fundamental to the austere aesthetics of early Modernist architects. Later, concrete construction was celebrated in Brutalist architecture, which accentuated the rawness of the building materials it employed. Concrete was used to give the buildings a rough quality. The concrete was made with a large aggregate and worked on, often painstakingly hammered, after it was cured to give it a rough texture.
Source: Natural Impressions: Wood-Formed Concrete Homes | Architizer