A concrete mixer truck is a large vehicle that is used to transport and mix concrete at a construction site. It typically consists of a truck chassis, a mixing drum, and a hydraulic system. The drum is rotated to mix the ingredients of the concrete as the truck is driven to the job site. Once on site, the drum is tilted to pour the concrete out of the truck, and the process is repeated until the entire load of concrete has been delivered. These types of trucks are commonly used in large construction projects, such as building bridges or high-rise buildings.