A mixer truck is a specialized truck used to transport concrete for construction; due to its shape, it is also often referred to as a conch truck or olive truck. These trucks are equipped with a cylindrical mixing drum to carry the mixed concrete. The drum is kept rotating during transportation to ensure that the concrete does not solidify. After the concrete is delivered, the interior of the mixing bowl is usually rinsed with water to prevent the residual concrete from hardening and taking up space, reducing the volume of the bowl.