A concrete mixer is commonly called a cement mixer. A concrete mixer is a device that evenly and consistently combines cement, sand or gravel and water to form concrete. A typical concrete mixer uses a revolving drum to mix components. Concrete mixers are also portable for smaller volume works. Special concrete transport trucks, known as in–transit mixers are made to transport and mix concrete up to the construction site. Concrete mixers as a rule do not travel far from their plant because the concrete begins to set soon.