Abstract: A system for pumping cement slurry comprising two pumps connected in parallel in a piping system, each pump comprising a flexible tubular bladder connected between two tubular elements and surrounded by a cylindrical housing so as to provide a closed annular space between the bladder and the housing. There is an inlet check valve and an outlet check valve on each of the two pumps. Pressure fluid is provided by a cylinder and power driven piston, which oscillates in the cylinder, from one end to the other. Each end of the cylinder is connected to one of the two annular spaces so that when the annular spaces and the cylinder are filled with pressure fluid, oscillation of the piston will cause sequential compression and expansion of the bladders, and pumping of cement slurry through the inlet check valves and out of the outlet check valves providing a substantially constant flow of slurry.