A concrete pumping unit comprising a pair of parallel piston pumps, alternately placed in communication with a concrete supply conduit and with a concrete delivery pipe, through a single baffle blade valve and respectively driven by coaxial fluid pressure piston cylinders is disclosed. The cylinders are interlocked with each other by a pipe which places in communication the chambers of said fluid pressure cylinders, opposite to the chambers in which the pressurized fluid is supplied and discharged through orifices near the ends of said cylinders. A hydraulic circuit is provided for placing a fluid supply pump, in communication with the fluid pressure piston cylinder performing the suction phase, while the orifice of the other fluid pressure piston cylinder is placed in communication through another circuit including, a four-way changeover electro-valve and an actuator distributor device with a discharge reservoir. The said actuator-distributor device comprises two hydraulic pistons and cylinders, operating in phase opposition, the piston rods of which are linked to the ends of a rocking bar, the pivot pin of which is integral with the spindle of the baffle blade valve. The hydraulic piston cylinders have closed ends and are each provided near each of its ends with an orifice. First orifices, positioned near one of the two ends of said cylinders are interconnected by a pipe, while second orifices which are arranged near the other ends are respectively connected by a respective pipe to the four-way changeover electrovalve. The electrovalve is connected to a fluid pump and to a pipe to return the fluid into the supply reservoir of said pump. A third orifice is arranged in an intermediate position relative to the first and second orifice of each hydraulic pump cylinder, and is positioned just downstream of the piston when it is reaches the limit position near the respective first orifice of the respective cylinder. The third orifices are connected respectively with one of the orifices for the supply of the fluid into or for the discharge of fluid from the fluid pressure piston cylinders. From the pipe interlocking the first orifices of said hydraulic distribution piston pumps there is a branch pipe directly connected to the fluid reservoir.