This document discusses concrete pumps and the properties of concrete suitable for pumping. It describes how piston pumps work, with a piston moving concrete from the hopper to the delivery valve. It also describes squeeze type concrete pumps, which use rotating blades and rollers to move concrete through a flexible pipe. Concrete pumps are advantageous when concrete must be transported long distances or to inaccessible areas. Proper concrete for pumping has a slump of 5.7-10 cm, water-cement ratio of 0.5-0.65, and uses well-graded aggregate under 20mm in size.